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Antoniou T, McCormack D, Tadrous M, Juurlink DN, Gomes T. The Risk of Ventricular Dysrhythmia or Sudden Death in Patients Receiving Serotonin Reuptake Inhibitors With Methadone: A Population-Based Study. Front Pharmacol 2022; 13:861953. [PMID: 35517813 PMCID: PMC9065276 DOI: 10.3389/fphar.2022.861953] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 03/11/2022] [Indexed: 11/13/2022] Open
Abstract
Background: Methadone is associated with ventricular dysrhythmias and sudden death. Serotonin reuptake inhibitors (SRIs) may increase the risk of these events either by inhibiting metabolism of methadone’s proarrhythmic (S)-enantiomer, additive QT interval prolongation, or both. We sought to determine whether certain SRIs were associated with a higher risk of methadone-related ventricular dysrhythmias or sudden death. Methods: We conducted a nested case-control study of Ontario residents receiving methadone between April 1, 1996 and December 31, 2017. Cases, defined as patients who died of sudden cardiac death or were hospitalized with a ventricular dysrhythmia while on methadone, were matched with up to four controls who also received methadone on age, sex, and a disease risk score. We determined the odds ratio (OR) and p-value functions for the association between methadone-related cardiotoxicity and treatment with SRIs known to inhibit metabolism of (S)-methadone (paroxetine, fluvoxamine, sertraline) or prolong the QT interval (citalopram and escitalopram). Patients who were not treated with an SRI served as the reference group. Results: During the study period, we identified 626 cases and 2,299 matched controls. Following multivariable adjustment, we found that recent use of sertraline, fluvoxamine or paroxetine (adjusted OR 1.30; 95% confidence intervals [CI] 0.90–1.86) and citalopram and escitalopram (adjusted OR 1.26; 95% CI 0.97–1.63) were associated with small increases in the risk methadone-related cardiac toxicity, an assertion supported by the corresponding p-value functions. Interpretation: Certain SRIs may be associated with a small increase in cardiac toxicity in methadone-treated patients.
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Affiliation(s)
- Tony Antoniou
- Department of Family and Community Medicine, Unity Health Toronto, Toronto, ON, Canada.,Li Ka Shing Knowledge Institute, Unity Health Toronto, Toronto, ON, Canada.,Department of Family and Community Medicine, University of Toronto, Toronto, ON, Canada.,Institute for Clinical Evaluative Sciences, Toronto, ON, Canada
| | | | - Mina Tadrous
- Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.,Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada.,Women's College Research Institute, Toronto, ON, Canada
| | - David N Juurlink
- Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.,Sunnybrook Research Institute, Toronto, ON, Canada.,Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Tara Gomes
- Li Ka Shing Knowledge Institute, Unity Health Toronto, Toronto, ON, Canada.,Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.,Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada.,Institute for Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada
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Abstract
Recently, the opioid analgesic d,l-methadone has gained much attention as a potential antineoplastic compound, considerably triggered through lay press and media. In consequence, physicians and pharmacists are currently confronted with numerous patients willing to use d,l-methadone against their malignancies. Well-performed in vitro and in vivo models have in fact shown pro-apoptotic effects of d,l-methadone or other opioids, but also proliferation-stimulating properties. Moreover, the mechanisms of proposed opioid-stimulated apoptosis are incompletely described or contradicting. Finally, the receptors mostly responsible for induction of apoptosis by d,l-methadone remain unclear as contributions of both µ-opioid receptors, Fas cell death receptors, toll-like receptors, N-Methyl-d-aspartate receptors and opioid growth factor receptors were suggested. Such ambiguity prevents rational application of d,l-methadone or patient stratification to enhance beneficial antineoplastic effects. From a clinical point of view, d,l-methadone and other opioids might in fact prolong survival, but such effects likely originate from their analgesic and neuro-psychotropic properties and, thus, improvements of quality of life. Crucial obstacles to the administration of d,l-methadone are incomplete knowledge about its systemic disposition, highly variable pharmacokinetics, profound drug-drug- or drug-disease interaction and QT-prolongation potential. This article summarizes and rates the pharmacological basis of d,l-methadone as an antineoplastic agent and puts its administration in clinical oncology into perspective. Despite enthralling experimental findings about d,l-methadone-mediated apoptosis in cancerous cells or tissues, clinicians should realize the current lack of evidence for the use of d,l-methadone as an antineoplastic agent. Its administration against cancer pain is, however, tenable, albeit restricted to certain clinical situations.
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Affiliation(s)
- Dirk Theile
- Department of Clinical Pharmacology and Pharmacoepidemiology, University Hospital Heidelberg, Im Neuenheimer Feld 410, Heidelberg, 69120, Germany
| | - Gerd Mikus
- Department of Clinical Pharmacology and Pharmacoepidemiology, University Hospital Heidelberg, Im Neuenheimer Feld 410, Heidelberg, 69120, Germany
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Kirby BJ, Symonds WT, Kearney BP, Mathias AA. Pharmacokinetic, Pharmacodynamic, and Drug-Interaction Profile of the Hepatitis C Virus NS5B Polymerase Inhibitor Sofosbuvir. Clin Pharmacokinet 2016; 54:677-90. [PMID: 25822283 DOI: 10.1007/s40262-015-0261-7] [Citation(s) in RCA: 187] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Sofosbuvir (SOVALDI(®)), a potent, once-daily, orally administered nucleotide analog prodrug inhibitor of the hepatitis C virus (HCV) NS5B polymerase is approved in the USA, EU, Canada, and other regions for the treatment of HCV infection as a component of an antiviral treatment regimen. Sofosbuvir undergoes intracellular activation to form GS-461203 (active triphosphate, not detected in plasma), and ultimately the inactive, renally eliminated metabolite GS-331007. GS-331007 was identified as the primary analyte of interest for clinical pharmacology studies as it accounted for >90 % of systemic drug-related material exposure, and provided comparable exposure-response relationships for viral kinetics as observed for sofosbuvir. GS-331007 and sofosbuvir exhibit linear pharmacokinetics with minimal accumulation upon multiple dosing. Compared to healthy subjects, HCV-infected patients had modestly lower (39 %) GS-331007 area under the plasma concentration-time curve (AUC) and higher sofosbuvir AUC (60 %). Sofosbuvir can be administered without dose modification in HCV-infected patients with any degree of hepatic impairment or mild to moderate renal impairment. Sofosbuvir has a low propensity for clinically significant drug interactions with common concomitant medications used by HCV-infected patients. Clinically significant alterations in GS-331007 or sofosbuvir exposures are limited to potent inducers of intestinal P-glycoprotein that may lower exposure. In HCV-infected patients, demographic variables do not significantly influence GS-331007 and sofosbuvir exposures and no consistent exposure-response relationships were observed for efficacy or safety. This review focuses on the clinical pharmacokinetics, pharmacodynamics, and pharmacokinetic-pharmacodynamic relationships of sofosbuvir, and summarizes a number of drug interaction studies with important concomitant medications commonly used by HCV-infected patients.
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Affiliation(s)
- Brian J Kirby
- Gilead Sciences Inc., 333 Lakeside Drive, Foster City, CA, 94404, USA
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Methadone’s effect on nAChRs—a link between methadone use and smoking? Biochem Pharmacol 2015; 97:542-549. [DOI: 10.1016/j.bcp.2015.07.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 07/23/2015] [Indexed: 12/17/2022]
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Chevillard L, Declèves X, Baud FJ, Risède P, Mégarbane B. Respiratory effects of diazepam/methadone combination in rats: a study based on concentration/effect relationships. Drug Alcohol Depend 2013; 131:298-307. [PMID: 23332448 DOI: 10.1016/j.drugalcdep.2012.12.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 12/12/2012] [Accepted: 12/18/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND Methadone may cause respiratory depression and fatalities. Concomitant use of benzodiazepines in methadone-treated patients for chronic pain or as maintenance therapy for opiate abuse is common. However, the exact contribution of benzodiazepines to methadone-induced respiratory toxicity remains debatable. METHODS We investigated the respiratory effects of the combination diazepam (20mg/kg)/methadone (5mg/kg) in the rat, focusing on methadone concentration/effect relationships. Respiratory effects were studied using arterial blood gases and whole-body plethysmography. Plasma concentrations of both R- and S-methadone enantiomers were measured using high-performance liquid chiral chromatography coupled to mass spectrometry. To clarify mechanisms of diazepam/methadone interaction, methadone metabolism was investigated in vitro using rat liver microsomes. RESULTS Diazepam/methadone co-administration significantly increased methadone-related effects on inspiratory time (p<0.001) but did not significantly alter the other respiratory parameters when compared with methadone alone, despite significant increase in the area under the curve of plasma R-methadone concentrations measured during 240 min (p<0.05). Diazepam/methadone co-incubation with microsomes in vitro resulted in a significant inhibition of methadone metabolism (p<0.01), with 50%-inhibitory diazepam concentrations of 25.02 ± 0.18 μmol/L and 25.18 ± 0.23 μmol/L for R- and S-methadone, respectively. CONCLUSION We concluded that co-administration of high-doses of diazepam and methadone in rats is not responsible for additional respiratory depression in comparison to methadone alone, despite significant metabolic interaction between the drugs. In humans, although our experimental data may suggest the relative safety of benzodiazepine/methadone co-prescription, physicians should remain cautious as other underlying conditions may enhance this drug-drug interaction.
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Affiliation(s)
- Lucie Chevillard
- INSERM U705, CNRS UMR8206, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, Neuropsychopharmacologie des addictions, Paris, France.
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Kapur BM, Hutson JR, Chibber T, Luk A, Selby P. Methadone: a review of drug-drug and pathophysiological interactions. Crit Rev Clin Lab Sci 2012; 48:171-95. [PMID: 22035341 DOI: 10.3109/10408363.2011.620601] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Numerous established and potential drug interactions with methadone are clinically important in people treated with methadone either for addiction or for chronic pain. Methadone users often have comorbidities and are prescribed drugs that may interact with methadone. Methadone is extensively metabolized by cytochrome P450 (CYP) 3A4 and to a lesser extent by CYP 1A2, 2D6, 2D8, 2C9/2C8, 2C19, and 2B6. Eighty-six percent of methadone is protein bound, predominately to α1-acid glycoprotein (AGP). Polymorphisms in or interactions with CYPs that metabolize methadone, changes in protein binding, and other pathophysiological conditions affect the pharmacokinetic properties of methadone. It is critical for health care providers who treat patients on methadone to have adequate information on the interactions of methadone with other drugs of abuse and other medications. We set out to describe drug-drug interactions as well as physiological and pathophysiological factors that may impact the pharmacokinetics of methadone. Using MEDLINE, we conducted a systematic search for papers and related abstracts published between 1966 and June 2010. Keywords that included methadone, drug-drug interactions, CYP P450 and AGP identified a total of 7709 papers. Other databases, including the Cochrane Database of Systematic Reviews and Scopus, were also searched; an additional 929 papers were found. Final selection of 286 publications was based on the relevance of each paper to the topic. Over 50 such interactions were found. Interactions of methadone with other drugs can lead to increased or decreased methadone drug levels in patients and result in potential overdose or withdrawal, respectively. The former can contribute to methadone's fatality. Prescribers of methadone and pharmacists should enquire about any new medications (including natural products and over-the-counter medications) periodically, and especially when an otherwise stable patient suddenly experiences drug craving, withdrawal or intoxication.
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Affiliation(s)
- Bhushan M Kapur
- Department of Clinical Pathology, Sunnybrook Health Sciences Centre, Toronto, Canada.
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The role of toxicology interpretations in prevention of sudden death. Forensic Sci Med Pathol 2012; 8:263-9. [DOI: 10.1007/s12024-011-9309-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2011] [Indexed: 11/25/2022]
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Tod M, Goutelle S, Clavel-Grabit F, Nicolas G, Charpiat B. Quantitative Prediction of Cytochrome P450 (CYP) 2D6-Mediated Drug Interactions. Clin Pharmacokinet 2011; 50:519-30. [DOI: 10.2165/11592620-000000000-00000] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Fonseca F, de la Torre R, Díaz L, Pastor A, Cuyàs E, Pizarro N, Khymenets O, Farré M, Torrens M. Contribution of cytochrome P450 and ABCB1 genetic variability on methadone pharmacokinetics, dose requirements, and response. PLoS One 2011; 6:e19527. [PMID: 21589866 PMCID: PMC3093392 DOI: 10.1371/journal.pone.0019527] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 04/06/2011] [Indexed: 12/22/2022] Open
Abstract
Although the efficacy of methadone maintenance treatment (MMT) in opioid dependence disorder has been well established, the influence of methadone pharmacokinetics in dose requirement and clinical outcome remains controversial. The aim of this study is to analyze methadone dosage in responder and nonresponder patients considering pharmacogenetic and pharmacokinetic factors that may contribute to dosage adequacy. Opioid dependence patients (meeting Diagnostic and Statistical Manual of Mental Disorders, [4(th) Edition] criteria) from a MMT community program were recruited. Patients were clinically assessed and blood samples were obtained to determine plasma concentrations of (R,S)-, (R) and (S)-methadone and to study allelic variants of genes encoding CYP3A5, CYP2D6, CYP2B6, CYP2C9, CYP2C19, and P-glycoprotein. Responders and nonresponders were defined by illicit opioid consumption detected in random urinalysis. The final sample consisted in 105 opioid dependent patients of Caucasian origin. Responder patients received higher doses of methadone and have been included into treatment for a longer period. No differences were found in terms of genotype frequencies between groups. Only CYP2D6 metabolizing phenotype differences were found in outcome status, methadone dose requirements, and plasma concentrations, being higher in the ultrarapid metabolizers. No other differences were found between phenotype and responder status, methadone dose requirements, neither in methadone plasma concentrations. Pharmacokinetic factors could explain some but not all differences in MMT outcome and methadone dose requirements.
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Affiliation(s)
- Francina Fonseca
- Institut de Neuropsiquiatria i Addiccions - Parc de Salut Mar, Barcelona, Spain
- Universitat Pompeu Fabra (CEXS-UPF), Barcelona, Spain
- Disorders by Use of Substances Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
| | - Rafael de la Torre
- Universitat Pompeu Fabra (CEXS-UPF), Barcelona, Spain
- Human Pharmacology and Clinical Neurosciences Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
- CIBER de Fisiopatología de la Obesidad y Nutrición (CB06/03), Hospital Clínico Universitario Santiago de Compostela, Santiago de Compostela, Spain
| | - Laura Díaz
- Institut de Neuropsiquiatria i Addiccions - Parc de Salut Mar, Barcelona, Spain
- Disorders by Use of Substances Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
| | - Antonio Pastor
- Human Pharmacology and Clinical Neurosciences Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
- Pharmacology Department, Autonomous University of Barcelona, Barcelona, Spain
| | - Elisabet Cuyàs
- Human Pharmacology and Clinical Neurosciences Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
- Pharmacology Department, Autonomous University of Barcelona, Barcelona, Spain
| | - Nieves Pizarro
- Human Pharmacology and Clinical Neurosciences Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
- Pharmacology Department, Autonomous University of Barcelona, Barcelona, Spain
| | - Olha Khymenets
- Human Pharmacology and Clinical Neurosciences Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
- CIBER de Fisiopatología de la Obesidad y Nutrición (CB06/03), Hospital Clínico Universitario Santiago de Compostela, Santiago de Compostela, Spain
| | - Magí Farré
- Human Pharmacology and Clinical Neurosciences Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
- Pharmacology Department, Autonomous University of Barcelona, Barcelona, Spain
| | - Marta Torrens
- Institut de Neuropsiquiatria i Addiccions - Parc de Salut Mar, Barcelona, Spain
- Disorders by Use of Substances Research Group, Neuropsychopharmacology Research Program, Institut Municipal d'Investigació Mèdica (IMIM-Hospital del Mar Research Institute), Barcelona, Spain
- Psychiatric Department, Autonomous University of Barcelona, Barcelona, Spain
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Saber-Tehrani AS, Bruce RD, Altice FL. Pharmacokinetic drug interactions and adverse consequences between psychotropic medications and pharmacotherapy for the treatment of opioid dependence. THE AMERICAN JOURNAL OF DRUG AND ALCOHOL ABUSE 2011; 37:1-11. [PMID: 21247284 DOI: 10.3109/00952990.2010.540279] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Psychiatric comorbidities among opioid-dependent patients are common. Many medications used to treat both conditions are metabolized through complimentary cytochrome P450 isoenzymes. When medication-assisted treatment for opioid dependence is concurrently used with psychotropic medications, problematic pharmacokinetic drug interactions may occur. METHODS We reviewed relevant English language articles identified through the MedLine, Scopus, and Embase databases from 1950 to December 2009 using the specific generic names of medications and keywords such as pharmacokinetics and drug interactions with buprenorphine, methadone, and naltrexone. Selected references from these articles were reviewed. Additionally, a review was conducted of abstracts and conference proceedings from national and international meetings from 1990 to 2009. A total of 60 studies were identified and reviewed. RESULTS Clinical case series and carefully controlled pharmacokinetic interaction studies have been conducted between methadone, buprenorphine, or naltrexone and some psychoactive medications. Important pharmacokinetic drug interactions have been demonstrated within each class of medications affecting either methadone and buprenorphine or psychoactive drugs. Few studies, however, have been conducted with naltrexone. CONCLUSIONS Several interactions between methadone, buprenorphine, or naltrexone and psychoactive medications are described and may have important clinical consequences. To optimize care, clinicians must be alerted to these interactions.
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Affiliation(s)
- Ali S Saber-Tehrani
- Yale University AIDS Program, Section of Infectious Diseases, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, CT 06510, USA
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Deaths involving contraindicated and inappropriate combinations of serotonergic drugs. Int J Legal Med 2010; 125:803-15. [PMID: 21120513 DOI: 10.1007/s00414-010-0536-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 11/18/2010] [Indexed: 12/23/2022]
Abstract
In the Australian state of Victoria, all fatalities that were recorded from 2002 through to 2008 involving the use of certain serotonin active drugs (tramadol, venlafaxine, fluoxetine, sertraline, citalopram and paroxetine), were reviewed to assess the incidence of contraindicated or ill advised drug combinations. More than 1,000 were identified of which 326 cases formed the basis of this study. These cases involved contraindicated or inappropriate drug combinations that can lead to adverse drug reactions (ADRs) and subsequent fatal toxicity. Of these, 46% were drug-related, 35% were a result of natural disease and 13% were classified as external injury cases. The remaining cases were those where the cause of death (COD) was unascertained. Tramadol was the most common drug, usually detected alongside a serotonergic antidepressant (in 20% of cases). Twenty-five (8%) cases involved contraindicated drug combinations while the remainder (301 cases, 92%) involved drug combinations that are associated with adverse interactions ranging from minor to major severity. Of these 326 cases, the Coroner determined 166 cases (51%) to be acts of intentional self-harm or drug misuse, with the remainder unascertained or attributed to natural disease. Very few post-mortem reports and Coroners' findings made mention of possible ADRs when such combinations were actually present. The majority of cases comprising contraindicated drug combinations involved the combined use of five drugs (24%) at the time of death. A combination of three to five drugs was most common in cases involving inadvisable drug combinations. Combined drug toxicity was the most common COD, with heart disease the most common co-morbidity.
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Review: Pharmacogenetic aspects of the effect of cytochrome P450 polymorphisms on serotonergic drug metabolism, response, interactions, and adverse effects. Forensic Sci Med Pathol 2010; 7:162-84. [PMID: 21052868 DOI: 10.1007/s12024-010-9188-3] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/05/2010] [Indexed: 12/26/2022]
Abstract
The field of pharmacogenetics contains a wealth of potential for the enhancement of clinical practice by providing a more effective match between patient and drug, consequently reducing the probability of an adverse drug reaction. Although a relatively novel concept in the forensic context, pharmacogenetics has the capability to assist in the interpretation of drug related deaths, particularly in unintentional drug poisonings where the cause of death remains unclear. However, the complex pharmacology of the drugs when subjected to genetic variations in metabolism makes interpretation of the expected response and adverse events difficult. Many possess multiple metabolic pathways, narrow therapeutic indices and active metabolites or enantiomers which may be eliminated via different pathways to the parent drug. A number of these drugs, which are metabolised primarily by the CYP450 system, are also associated with serotonin syndrome, or serotonin toxicity, especially when used concomitantly with other serotonin active drugs which rely on the same metabolic pathways for drug elimination. A comprehensive understanding of polymorphic drug metabolism and its expected outcomes is therefore essential when interpreting the involvement of drugs in adverse reactions. This review examines the genetically variable CYP450-mediated metabolism of a number of serotonin-active drugs that are often implicated in cases of serotonin toxicity, to assess the impact of pharmacogenetics on drug metabolism, response, interactions and adverse effects.
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Pilgrim J, Gerostamoulos D, Drummer OH. Deaths involving serotonergic drugs. Forensic Sci Int 2010; 198:110-7. [DOI: 10.1016/j.forsciint.2010.01.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2009] [Revised: 12/22/2009] [Accepted: 01/23/2010] [Indexed: 10/19/2022]
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Zhou SF, Liu JP, Chowbay B. Polymorphism of human cytochrome P450 enzymes and its clinical impact. Drug Metab Rev 2009; 41:89-295. [PMID: 19514967 DOI: 10.1080/03602530902843483] [Citation(s) in RCA: 502] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.
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Affiliation(s)
- Shu-Feng Zhou
- School of Health Sciences, RMIT University, Bundoora, Victoria, Australia.
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Shiran MR, Lennard MS, Iqbal MZ, Lagundoye O, Seivewright N, Tucker GT, Rostami-Hodjegan A. Contribution of the activities of CYP3A, CYP2D6, CYP1A2 and other potential covariates to the disposition of methadone in patients undergoing methadone maintenance treatment. Br J Clin Pharmacol 2009; 67:29-37. [PMID: 19133059 DOI: 10.1111/j.1365-2125.2008.03312.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
AIMS To investigate the influence of different cytochrome P450 (CYP) activities and other potential covariates on the disposition of methadone in patients on methadone maintenance therapy (MMT). METHODS Eighty-eight patients (58 male; 21-55 years; 84 White) on MMT were studied. CYP2D6 activity [3 h plasma metabolic ratio of dextromethorphan (DEX) to dextrorphan (DOR)] was determined in 44 patients (29 male; 24-55 years), CYP1A2 activity (salivary caffeine elimination half-life) in 44 patients (21 male; 24-55 years) and CYP3A activity (oral clearance of midazolam) in 49 patients (33 male; 23-55 years). Data on all three CYPs were obtained from 32 subjects. Total plasma concentrations of (RS)-methadone and total and unbound plasma concentrations of both enantiomers were measured by LC/MS. Population pharmacokinetics and subsequent multiple regression analysis were used to calculate methadone oral clearance and to identify its covariates. RESULTS Between 61 and 68% of the overall variation in total plasma trough concentrations of (RS)-, (R)- and (S)-methadone was explained by methadone dose, duration of addiction before starting MMT, CYP3A activity and illicit morphine use. CYP3A activity explained 22, 16, 15 and 23% of the variation in unbound (R)-, unbound (S)-, total (RS)- and total (S)-methadone clearances, respectively. Neither CYP2D6 nor CYP1A2 activity was related to methadone disposition. CONCLUSIONS CYP3A activity has a modest influence on methadone disposition. Inhibitors and inducers of this enzyme should be monitored in patients taking methadone.
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Affiliation(s)
- Mohammad-Reza Shiran
- Academic Unit of Clinical Pharmacology, University of Sheffield and Sheffield Care Trust, Substance Misuse Services, Sheffield, UK
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Abstract
Opioids have been used for centuries to treat a variety of psychiatric conditions with much success. The so-called "opium cure" lost popularity in the early 1950s with the development of non-addictive tricyclic antidepressants and monoamine oxidase inhibitors. Nonetheless, recent literature supports the potent role of methadone, buprenorphine, tramadol, morphine, and other opioids as effective, durable, and rapid therapeutic agents for anxiety and depression. This article reviews the medical literature on the treatment of psychiatric disorders with opioids (notably, methadone and buprenorphine) in both the non-opioid-dependent population and in the opioid-dependent methadone maintenance population. The most recent neurotransmitter theories on the origin of depression and anxiety will be reviewed, including current information on the role of serotonin, N-Methyl d-Aspartate, glutamate, cortisol, catecholamine, and dopamine in psychiatric disorders. The observation that methadone maintenance patients with co-existing psychiatric morbidity (so called dual diagnosis patients) require substantially higher methadone dosages by between 20% and 50% will be explored and qualified. The role of methadone and other opioids as beneficial psychiatric medications that are independent of their drug abuse mitigating properties will be discussed. The mechanisms by which methadone and other opioids can favorably modulate the neurotransmitter systems controlling mood will also be discussed.
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Affiliation(s)
- Peter L Tenore
- Albert Einstein College of Medicine, Division of Substance Abuse, Department of Psychiatry, 1500 Waters Place, Bronx, NY 10461, USA.
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Clinically relevant pharmacokinetic drug interactions with second-generation antidepressants: an update. Clin Ther 2008; 30:1206-27. [PMID: 18691982 DOI: 10.1016/s0149-2918(08)80047-1] [Citation(s) in RCA: 250] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND The second-generation antidepressants include selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), and other compounds with different mechanisms of action. All second-generation antidepressants are metabolized in the liver by the cytochrome P450 (CYP) enzyme system. Concomitant intake of inhibitors or inducers of the CYP isozymes involved in the biotransformation of specific antidepressants may alter plasma concentrations of these agents, although this effect is unlikely to be associated with clinically relevant interactions. Rather, concern about drug interactions with second-generation antidepressants is based on their in vitro potential to inhibit > or = 1 CYP isozyme. OBJECTIVE The goal of this article was to review the current literature on clinically relevant pharmacokinetic drug interactions with second-generation antidepressants. METHODS A search of MEDLINE and EMBASE was conducted for original research and review articles published in English between January 1985 and February 2008. Among the search terms were drug interactions, second-generation antidepressants, newer antidepressants, SSRIs, SNRIs, fluoxetine, paroxetine, fluvoxamine, sertraline, citalopram, escitalopram, venlafaxine, duloxetine, mirtazapine, reboxetine, bupropion, nefazodone, pharmacokinetics, drug metabolism, and cytochrome P450. Only articles published in peer-reviewed journals were included, and meeting abstracts were excluded. The reference lists of relevant articles were hand-searched for additional publications. RESULTS Second-generation antidepressants differ in their potential for pharmacokinetic drug interactions. Fluoxetine and paroxetine are potent inhibitors of CYP2D6, fluvoxamine markedly inhibits CYP1A2 and CYP2C19, and nefazodone is a substantial inhibitor of CYP3A4. Therefore, clinically relevant interactions may be expected when these antidepressants are coadministered with substrates of the pertinent isozymes, particularly those with a narrow therapeutic index. Duloxetine and bupropion are moderate inhibitors of CYP2D6, and sertraline may cause significant inhibition of this isoform, but only at high doses. Citalopram, escitalopram, venlafaxine, mirtazapine, and reboxetine are weak or negligible inhibitors of CYP isozymes in vitro and are less likely than other second-generation antidepressants to interact with co-administered medications. CONCLUSIONS Second-generation antidepressants are not equivalent in their potential for pharmacokinetic drug interactions. Although interactions may be predictable in specific circumstances, use of an antidepressant with a more favorable drug-interaction profile may be justified.
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Li Y, Kantelip JP, Gerritsen-van Schieveen P, Davani S. Interindividual variability of methadone response: impact of genetic polymorphism. Mol Diagn Ther 2008; 12:109-24. [PMID: 18422375 DOI: 10.1007/bf03256276] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Methadone, an opioid analgesic, is used clinically in pain therapy as well as for substitution therapy in opioid addiction. It has a large interindividual variability in response and a narrow therapeutic index. Genetic polymorphisms in genes coding for methadone-metabolizing enzymes, transporter proteins (p-glycoprotein; P-gp), and mu-opioid receptors may explain part of the observed interindividual variation in the pharmacokinetics and pharmacodynamics of methadone. Cytochrome P450 (CYP) 3A4 and 2B6 have been identified as the main CYP isoforms involved in methadone metabolism. Methadone is a P-gp substrate, and, although there are inconsistent reports, ABCB1 genetic polymorphisms also contribute slightly to the interindividual variability of methadone kinetics and influence dose requirements. Genetic polymorphism is the cause of high interindividual variability of methadone blood concentrations for a given dose; for example, in order to obtain methadone plasma concentrations of 250 ng/mL, doses of racemic methadone as low as 55 mg/day or as high as 921 mg/day can be required in a 70-kg patient without any co-medication. The clinician must be aware of the pharmacokinetic properties and pharmacological interactions of methadone in order to personalize methadone administration. In the future, pharmacogenetics, at a limited level, can also be expected to facilitate individualized methadone therapy.
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Affiliation(s)
- Yongfang Li
- Department of Clinical Pharmacology and Toxicology, University Hospital Besançon, Besançon, France
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Weschules DJ, Bain KT, Richeimer S. Actual and potential drug interactions associated with methadone. PAIN MEDICINE 2008; 9:315-44. [PMID: 18386306 DOI: 10.1111/j.1526-4637.2006.00289.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVE To identify and characterize methadone-related drug interactions, as well as factors accounting for the variability in manifesting these interactions clinically. DESIGN Systematic review of the primary literature. METHODS Over 200 articles, reports of clinical trials, and case reports were reviewed. Studies and case reports were included if they revealed either quantitative or qualitative methods to identify, evaluate severity of, or compare methadone-related drug interactions. RESULTS OF DATA SYNTHESIS The evidence base associated with methadone drug interactions is underdeveloped in general, as the majority of references found were case reports or case series. Most of the studies and reports focused on inpatients receiving methadone maintenance treatment (MMT) that were between 20 and 60 years of age, taking 200 mg/day of methadone or less. Evidence supporting the involvement of lesser known cytochrome P450 enzymes such as 2B6 is emerging, which may partially explain the inconsistencies previously found in studies looking specifically at 3A4 in vitro and in vivo. Genetic variability may play a role in the pharmacokinetics and pharmacodynamics of many medications, including methadone. CONCLUSIONS Drug interactions associated with methadone and their clinical significance are still poorly understood in general. Many tertiary drug information references and review articles report interactions associated with methadone in a general sense, much of which is theoretical and not verified by case reports, much less well-designed clinical trials. The majority of drug interaction reports that do exist were performed in the MMT population, which may differ significantly from chronic pain or cancer pain populations.
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Uehlinger C, Crettol S, Chassot P, Brocard M, Koeb L, Brawand-Amey M, Eap CB. Increased (R)-methadone plasma concentrations by quetiapine in cytochrome P450s and ABCB1 genotyped patients. J Clin Psychopharmacol 2007; 27:273-8. [PMID: 17502774 DOI: 10.1097/jcp.0b013e3180592ad2] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Steady-state plasma concentrations of (R)- (ie, the active form), (S)-, and (R,S)-methadone were measured in 14 addict patients in methadone maintenance treatment, before and after introduction of quetiapine, administered at a mean dosage of 138 mg/d (SD, 87 mg/d; median, 125 mg/d; range, 50-300 mg/d) during a mean period of 30 days (SD, 8 days; median, 30 days; range, 20-48 days). Eleven patients were genotyped as being CYP2D6 extensive metabolizers (EMs) and 3 patients as poor metabolizers. Eleven patients had the ABCB1 3435 CT or CC genotypes, and 3 patients had the ABCB1 3435 TT genotype, the latter genotype being associated with lower P-glycoprotein activity. Quetiapine significantly increases (R)-methadone concentration-dose ratios in the whole group [increase for (R)-methadone: mean, +21%; SD, +28%; median, +13%; range, -23% to +85%; P = 0.026], but not for (S)-methadone (mean, +23%; SD, +43%; median, +6%; range, -30% to +115%; P = 0.12) or for (R,S)-methadone (mean, +21%; SD, +34%; median, +9%; range, -21% to +95%; P = 0.064). The mean increases of (R)-methadone concentration-dose ratios were of 7%, 21%, and 30% in the CYP2D6 poor metabolizers, heterozygous EMs, and homozygous EMs, respectively, whereas they were of 3%, 23%, and 33% in the subjects with the ABCB1 3435 TT, CT, and CC genotypes, respectively. Thus, quetiapine increases the plasma concentrations of (R)-methadone, possibly in part by an interaction with CYP2D6 and/or with the P-glycoprotein transporter system. No signs of overmedication caused by increased methadone plasma concentrations were noticed by the staff or reported by the patients.
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Affiliation(s)
- Claude Uehlinger
- Centre Psychosocial, Unité de Traitement des Addictions, Fribourg, Switzerland
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Crettol S, Monnat M, Eap CB. Could pharmacogenetic data explain part of the interindividual sensitivity to methadone-induced respiratory depression? CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2007; 11:119. [PMID: 17338832 PMCID: PMC2151888 DOI: 10.1186/cc5699] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In this issue of Critical Care, Megarbane and colleagues present a case report of methadone-induced respiratory depression and conduct a toxicokinetic/toxicodynamic evaluation. An opioid-dependent patient receiving methadone maintenance treatment (daily dose 70 mg) was found unconscious after ingesting 240 mg methadone and 2 mg flunitrazepam. Significant improvement in consciousness was achieved after an intravenous bolus of 0.3 mg naloxone followed by a continuous infusion of naloxone at 0.3 mg/hour. In patients receiving methadone maintenance treatment, an occasional intake of two to four times the usual daily dose of methadone is not an exceptional occurrence. However, few such patients experience episodes of life-threatening respiratory depression. Here, we discuss whether recent pharmacogenetic data could help us to understand interindividual variability in sensitivity to respiratory depression and, ultimately, to predict which patients are most likely to be affected.
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Affiliation(s)
- Séverine Crettol
- Unit of Biochemistry and Clinical Psychopharmacology, Centre for Psychiatric Neurosciences, University Psychiatry Department, Cery Hospital, CH-1008 Prilly-Lausanne, Switzerland
| | - Martine Monnat
- Center St Martin, Unit of toxicodependency, University Psychiatry Department, Rue St-Martin 7, CH-1003 Lausanne, Switzerland
| | - Chin B Eap
- Unit of Biochemistry and Clinical Psychopharmacology, Centre for Psychiatric Neurosciences, University Psychiatry Department, Cery Hospital, CH-1008 Prilly-Lausanne, Switzerland
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Abstract
Opioids are used for acute and chronic pain and dependency. They have a narrow therapeutic index and large interpatient variability in response. Genetic factors regulating their pharmacokinetics (metabolizing enzymes, transporters) and pharmacodynamics (receptors and signal transduction elements) are contributors to such variability. The polymorphic CYP2D6 regulates the O-demethylation of codeine and other weak opioids to more potent metabolites with poor metabolizers having reduced antinociception in some cases. Some opioids are P-glycoprotein substrates, whereas, ABCB1 genotypes inconsistently influence opioid pharmacodynamics and dosage requirements. Single-nucleotide polymorphisms in the mu opioid receptor gene are associated with increasing morphine, but not methadone dosage requirements and altered efficacy of mu opioid agonists and antagonists. As knowledge regarding the interplay between genes affecting opioid pharmacokinetics including cerebral kinetics and pharmacodynamics increases, our understanding of the role of pharmacogenomics in mediating interpatient variability in efficacy and side effects to this important class of drugs will be better informed. Opioid drugs as a group have withstood the test of time in their ability to attenuate acute and chronic pain. Since the isolation of morphine in the early 1800s by Friedrich Sertürner, a large number of opioid drugs beginning with modification of the 4,5-epoxymorphinan ring structure were developed in order to improve their therapeutic margin, including reducing dependence and tolerance, ultimately without success.
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Affiliation(s)
- Andrew A Somogyi
- Discipline of Pharmacology, School of Medical Sciences, University of Adelaide, Adelaide, Australia.
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Liu P, Foster G, Labadie R, Somoza E, Sharma A. Pharmacokinetic interaction between voriconazole and methadone at steady state in patients on methadone therapy. Antimicrob Agents Chemother 2006; 51:110-8. [PMID: 17074798 PMCID: PMC1797667 DOI: 10.1128/aac.00559-06] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This trial was aimed to estimate the pharmacokinetic interaction between voriconazole and methadone at steady state in male patients on methadone therapy and to characterize the safety and tolerability profile during the coadministration. Twenty-three patients on individualized methadone therapy (30 to 100 mg once daily) were enrolled into this randomized, patient- and investigator-blind, placebo-controlled, parallel-group study. Methadone pharmacokinetic samples were collected from patients receiving methadone alone as the baseline before they were randomized to coadminister either 200 mg voriconazole twice daily (BID) (400-mg BID loading doses on the first day) (n = 16) or matching placebo (n = 7) for the next 5 days. Pharmacokinetic samples for methadone and voriconazole were collected on the last day of voriconazole dosing. The safety data were collected throughout the study. Voriconazole increased the steady-state exposure of pharmacologically active enantiomer (R)-methadone: the mean area under the concentration-time curve from 0 to 24 h (AUC(0-24)) was increased by 47.2% (90% confidence intervals [CI]: 37.7%, 57.4%), and the mean peak concentration (C(max)) was increased by 30.7% (90% CI: 22.2%, 39.8%). The magnitude of increase in (S)-methadone exposure was greater than that of (R)-methadone: the AUC(0-24) was increased by 103.4% (90% CI: 85.0%, 123.6%), and the C(max) was increased by 65.4% (90% CI: 52.6%, 79.2%). Methadone appeared to have no effect on the steady-state voriconazole pharmacokinetics compared to the historical data for voriconazole alone. Methadone patients receiving voriconazole showed no signs or symptoms of significant opioid withdrawal or overdose. Coadministration of 200 mg voriconazole BID with methadone was generally safe and well tolerated. Nevertheless, caution should be exercised when voriconazole is coadministered with methadone due to the increase in (R)-methadone exposure, which in turn may require a dose reduction of methadone.
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Affiliation(s)
- Ping Liu
- Department of Clinical Pharmacology, Pfizer Global Research and Development, 50 Pequot Avenue, New London, CT 06320, USA
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26
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Elsayem A, Bruera E. Methadone-induced respiratory depression in a patient with a history of alcoholism. J Palliat Med 2006; 8:1062-6. [PMID: 16238524 DOI: 10.1089/jpm.2005.8.1062] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Ahmed Elsayem
- Department of Palliative Care and Rehabilitation Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas.
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Waxmonsky JG, Wilens TE. Pharmacotherapy of adolescent substance use disorders: a review of the literature. J Child Adolesc Psychopharmacol 2005; 15:810-25. [PMID: 16262597 DOI: 10.1089/cap.2005.15.810] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Substance use disorders (SUD) are increasingly conceptualized as developing during adolescence. Moreover, adolescent SUD are viewed as one of the most difficult mental health conditions to treat. The role of pharmacotherapy for adolescents with SUD is not well delineated. We systematically reviewed existing pharmacotherapy studies of adolescent SUD. METHODS A computerized search of the literature addressing the pharmacotherapy of SUD in adolescents was performed. Data from relevant peer-reviewed scientific presentations were also included. RESULTS Five case reports (n = 8 subjects), six open studies that primarily addressed SUD with comorbid psychiatric disorders (n = 73 subjects), and five placebo-controlled studies (n = 156 subjects) on the pharmacological treatment of youths with SUD were identified. Pharmacological agents appear to reduce comorbid psychopathology with a milder reduction in SUD symptoms. The most robust evidence exists for the treatment of SUD comorbid with affective disorders. There is a limited database supporting the use of agents to reduce substance craving and the preventative effects of pharmacotherapy on subsequent SUD development in adolescents with specific psychiatric disorders. CONCLUSION Further controlled studies directed at reducing drug use and craving, and guiding the integration of pharmacotherapy and psychosocial interventions for SUD with the treatment of comorbid psychiatric illness, are necessary.
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Asnis GM, De La Garza R. Interferon-induced depression: strategies in treatment. Prog Neuropsychopharmacol Biol Psychiatry 2005; 29:808-18. [PMID: 15907352 DOI: 10.1016/j.pnpbp.2005.03.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/01/2005] [Indexed: 12/17/2022]
Abstract
Interferon (IFN) is a pro-inflammatory cytokine that is widely used for the treatment of a number of disorders including viral infections, hematological proliferative disorders, and skin malignancies. Unfortunately, IFN frequently induced depression and has led to compromised tolerability with lowering of the dose of IFN and even discontinuation of treatment. Thus, it is imperative to diagnose IFN-induced depression early, evaluate whether this depression is associated with IFN-induced anemia or thyroid dysfunction, which can be corrected, and if necessary treat with antidepressants. IFN-induced depression is highly responsive to antidepressants with benefits occurring frequently at relatively low doses and after only a few weeks. Although SSRIs have mainly been studied, non-SSRIs appear to be effective also. Antidepressants have a number of risks and side effects that must be considered and may enter into the decision as to which antidepressant to choose. If IFN induces a depression in a patient with a bipolar disorder history, antidepressant treatment must include a mood stabilizer. In the case of vulnerable patients (e.g., those who have significant depressive symptoms prior to IFN or who have had an IFN-induced depression in the past) prophylactic antidepressant treatment appears to decrease the likelihood of having an IFN-induced depression. On the basis of known and effective treatment strategies, IFN-induced depression should not be an obstacle for continued treatment in most patient populations.
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Affiliation(s)
- Gregory M Asnis
- Albert Einstein College of Medicine, Montefiore Medical Center, Anxiety and Depression Program, 111 E. 210th Street, Bronx, NY, USA.
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Draper JC, McCance-Katz EF. Medical illness and comorbidities in drug users: implications for addiction pharmacotherapy treatment. Subst Use Misuse 2005; 40:1899-921, 2043-8. [PMID: 16282085 DOI: 10.1080/10826080500294775] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Providing effective medical care to those with substance use disorders can be a challenge to clinicians. In this article, we briefly summarize issues that occur frequently in the medical treatment of substance users. The focus of this article is twofold. The first is to briefly summarize common co-occurring medical illnesses in those manifesting substance use disorders with an emphasis on issues related to providing effective treatment for these diseases in this population. Using specific examples of frequently occurring comorbid medical illness in substance users, including infectious diseases (hepatitis C and HIV disease), sexually transmitted diseases, and pregnancy as examples, the complexities of medical care for this population is demonstrated. Second, this article addresses some of the difficulties encountered in pharmacotherapy aimed specifically at treatment of substance use disorders. For example, difficulties in managing concomitant opiate therapy in those requiring medications for medical illness that may have strong and adverse interactions with opiates are addressed. Adverse events reported for some substance use disorder pharmacotherapies are also highlighted. We conclude with a brief review of models of care that have been effective in addressing the needs of this challenging population that can provide additional means for enhancing the clinical care of substance users.
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Affiliation(s)
- Joy C Draper
- Department of Obstetrics and Gynecology, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23219, USA
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Corkery JM, Schifano F, Ghodse AH, Oyefeso A. The effects of methadone and its role in fatalities. Hum Psychopharmacol 2004; 19:565-76. [PMID: 15378662 DOI: 10.1002/hup.630] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Methadone is a synthetic opioid, used both as an analgesic in severe pain relief and now mainly in the treatment of opiate dependence. Such use of the drug has increased as its advantages have become widely recognized. There are undesirable outcomes from its greater use, including a substantial market in diverted methadone and a high number of deaths where the drug has been implicated. It is important to understand how and why methadone causes death so that such fatalities can be minimized, and to disseminate such information. This paper presents an overview of the chief effects of methadone on the human body, considering its metabolism, drug interactions and tolerance. The principal mechanisms by which methadone causes death are discussed: respiratory depression, aspiration of vomit, pulmonary oedema, bronchopneumonia, cardiac problems and renal failure. Many such deaths are preventable, if drug interactions and polydrug use are avoided, its longer period of metabolism and individuals' tolerance levels are considered. It is hoped that this paper will (a) help guide health professionals in their management and treatment of patients participating in methadone treatment programmes, and (b) provide some basic information for those dealing with individuals who have consumed methadone.
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Affiliation(s)
- John M Corkery
- National Programme on Substance Abuse Deaths, Department of Mental Health-Addictive Behaviour, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK.
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Foster DJR, Somogyi AA, White JM, Bochner F. Population pharmacokinetics of (R)-, (S)- and rac-methadone in methadone maintenance patients. Br J Clin Pharmacol 2004; 57:742-55. [PMID: 15151520 PMCID: PMC1884530 DOI: 10.1111/j.1365-2125.2004.02079.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
AIM To construct a population pharmacokinetic model for methadone enantiomers in the setting of methadone maintenance treatment for opioid dependence. METHODS A population pharmacokinetic model was developed using P-Pharm software for rac-, (R)- and (S)-methadone using data (8-13 plasma samples per subject) obtained from 59 methadone maintenance patients during one interdosing interval at steady state. The patients were randomly assigned to either a development (n = 38) or a validation dataset (n = 21). The model was refined by inclusion of all subjects to construct a final basic model, which was used to construct a covariate model. RESULTS A population-based two-compartment open model with first-order absorption and lag time was developed and validated for all analytes. The population geometric mean (coefficient of variation) of maximum a posteriori probability Bayesian estimated values for clearance, terminal half-life and volume of distribution at steady-state of the active (R)-enantiomer were 8.7 (42%) l h(-1), 51 (45%) h and 597 (45%) l, respectively. For all analytes, the volume of the central compartment was decreased with increasing plasma alpha(1)-acid glycoprotein concentration and was lower in females, while the delay in absorption was longer at higher doses. No covariates were identified for apparent oral clearance. The apparent oral clearance of (R)-methadone (geometric mean ratio; 95% confidence interval) was 105% (99, 110), that of (S)-methadone (P = 0.19), while (R)-methadone V(c)/F (154%; 151, 157), V(dss) /F (173%; 164, 183), t(1/2beta) (162%; 153, 172) and mean residence time (166%; 156, 176) were significantly greater (P < 0.0001) than for (S)-methadone. The population pharmacokinetic models were able to predict accurately oral clearance values from limited (one or two samples) blood sampling protocols. CONCLUSIONS The substantial stereoselectivity in methadone disposition reinforces the potential for misinterpretation of racemic methadone disposition data. The marked interindividual variability in (R)-methadone clearance, with no covariates identified, highlights the need for alternative methods to determine an individual's metabolic clearance. The ability to predict (R)-methadone clearance from one to two blood samples at steady state may prove clinically useful if a drug-drug interaction or poor adherence are suspected and guide the prescriber in deciding if a client's request for a dose increase is warranted or whether an alternative opioid would be more appropriate.
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Affiliation(s)
- David J R Foster
- Department of Clinical and Experimental Pharmacology, The University of Adelaide, Adelaide 5005, Australia.
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Suspected Pharmacological Interactions in a Cancer Patient During Methadone Maintenance. ADDICTIVE DISORDERS & THEIR TREATMENT 2004. [DOI: 10.1097/00132576-200406000-00006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Abstract
New psychotropic drugs introduced in clinical practice in recent years include new antidepressants, such as selective serotonin reuptake inhibitors (SSRI) and 'third generation' antidepressants, and atypical antipsychotics, i.e. clozapine, risperidone, olanzapine, quetiapine, ziprasidone and amisulpride. These agents are extensively metabolized in the liver by cytochrome P450 (CYP) enzymes and are therefore susceptible to metabolically based drug interactions with other psychotropic medications or with compounds used for the treatment of concomitant somatic illnesses. New antidepressants differ in their potential for metabolic drug interactions. Fluoxetine and paroxetine are potent inhibitors of CYP2D6, fluvoxamine markedly inhibits CYP1A2 and CYP2C19, while nefazodone is a potent inhibitor of CYP3A4. These antidepressants may be involved in clinically significant interactions when coadministered with substrates of these isoforms, especially those with a narrow therapeutic index. Other new antidepressants including sertraline, citalopram, venlafaxine, mirtazapine and reboxetine are weak in vitro inhibitors of the different CYP isoforms and appear to have less propensity for important metabolic interactions. The new atypical antipsychotics do not affect significantly the activity of CYP isoenzymes and are not expected to impair the elimination of other medications. Conversely, coadministration of inhibitors or inducers of the CYP isoenzymes involved in metabolism of the various antipsychotic compounds may alter their plasma concentrations, possibly leading to clinically significant effects. The potential for metabolically based drug interactions of any new psychotropic agent may be anticipated on the basis of knowledge about the CYP enzymes responsible for its metabolism and about its effect on the activity of these enzymes. This information is essential for rational prescribing and may guide selection of an appropriate compound which is less likely to interact with already taken medication(s).
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Affiliation(s)
- Edoardo Spina
- Department of Clinical and Experimental Medicine and Pharmacology, Section of Pharmacology, University of Messina, Policlinico Universitario, Via Consolare Valeria, 98125 Messina, Italy.
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Wang JS, DeVane CL. Involvement of CYP3A4, CYP2C8, and CYP2D6 in the metabolism of (R)- and (S)-methadone in vitro. Drug Metab Dispos 2003; 31:742-7. [PMID: 12756206 DOI: 10.1124/dmd.31.6.742] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To clarify the oxidative metabolism of methadone (R)- and (S)-enantiomers, the depletion of parent (R)- and (S)-methadone and the formation of racemic 2-ethylidene-1,5-dimethyl-3,3-diphe-nylpyrolidine were studied using human liver microsomes and recombinant cytochrome P450 enzymes. Based on studies with isoform-selective chemical inhibitors and expressed enzymes, CYP3A4 was the predominant enzyme involved in the metabolism of (R)-methadone. However, it has different stereoselectivity toward (R)- and (S)-methadone. In recombinant CYP3A4, the metabolic clearance of (R)-methadone was about 4-fold higher than that of (S)-methadone. CYP2C8 is also involved in the metabolism of methadone, but its contribution to the metabolism of (R)-methadone was smaller than that of CYP3A4. But for the metabolism of (S)-methadone, the roles of CYP2C8 and CYP3A4 appeared equal. Although CYP2D6 is involved in the metabolism of (R)- and (S)-methadone, its role was smaller compared with CYP3A4 and CYP2C8. Using clinically relevant concentrations of ketoconazole (1 microM, selective CYP3A4 inhibitor), trimethoprim (100 microM, selective CYP2C8 inhibitor), and paroxetine (5 microM, potent CYP2D6 inhibitor), these inhibitors decreased the hepatic metabolism of (R)-[(S)-]methadone by 69% (47%), 22% (51%), and 41% (77%), respectively. However, inhibition of the metabolism of (R)- and (S)-methadone by paroxetine was due to inhibition not only of CYP2D6, but also CYP3A4 and, to a minor extent, CYP2C8. The present in vitro findings indicated that CYP3A4, CYP2C8, and CYP2D6 are all involved in the stereoselective metabolism of methadone (R)- and (S)-enantiomers. These data suggest that coadministration of inhibitors of CYP3A4 and CYP2C8 may produce clinically significant drug-drug interactions with methadone.
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Affiliation(s)
- Jun-Sheng Wang
- Laboratory of Drug Disposition & Pharmacogenetics, Institute of Psychiatry, Medical University of South Carolina, 67 President St, Suite 246 North, Charleston, SC 29425, USA
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Eap CB, Buclin T, Baumann P. Interindividual variability of the clinical pharmacokinetics of methadone: implications for the treatment of opioid dependence. Clin Pharmacokinet 2003; 41:1153-93. [PMID: 12405865 DOI: 10.2165/00003088-200241140-00003] [Citation(s) in RCA: 396] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Methadone is widely used for the treatment of opioid dependence. Although in most countries the drug is administered as a racemic mixture of (R)- and (S)- methadone, (R)-methadone accounts for most, if not all, of the opioid effects. Methadone can be detected in the blood 15-45 minutes after oral administration, with peak plasma concentration at 2.5-4 hours. Methadone has a mean bioavailability of around 75% (range 36-100%). Methadone is highly bound to plasma proteins, in particular to alpha(1)-acid glycoprotein. Its mean free fraction is around 13%, with a 4-fold interindividual variation. Its volume of distribution is about 4 L/kg (range 2-13 L/kg). The elimination of methadone is mediated by biotransformation, followed by renal and faecal excretion. Total body clearance is about 0.095 L/min, with wide interindividual variation (range 0.02-2 L/min). Plasma concentrations of methadone decrease in a biexponential manner, with a mean value of around 22 hours (range 5-130 hours) for elimination half-life. For the active (R)-enantiomer, mean values of around 40 hours have been determined. Cytochrome P450 (CYP) 3A4 and to a lesser extent 2D6 are probably the main isoforms involved in methadone metabolism. Rifampicin (rifampin), phenobarbital, phenytoin, carbamazepine, nevirapine, and efavirenz decrease methadone blood concentrations, probably by induction of CYP3A4 activity, which can result in severe withdrawal symptoms. Inhibitors of CYP3A4, such as fluconazole, and of CYP2D6, such as paroxetine, increase methadone blood concentrations. There is an up to 17-fold interindividual variation of methadone blood concentration for a given dosage, and interindividual variability of CYP enzymes accounts for a large part of this variation. Since methadone probably also displays large interindividual variability in its pharmacodynamics, methadone treatment must be individually adapted to each patient. Because of the high morbidity and mortality associated with opioid dependence, it is of major importance that methadone is used at an effective dosage in maintenance treatment: at least 60 mg/day, but typically 80-100 mg/day. Recent studies also show that a subset of patients might benefit from methadone dosages larger than 100 mg/day, many of them because of high clearance. In clinical management, medical evaluation of objective signs and subjective symptoms is sufficient for dosage titration in most patients. However, therapeutic drug monitoring can be useful in particular situations. In the case of non-response trough plasma concentrations of 400 microg/L for (R,S)-methadone or 250 microg/L for (R)-methadone might be used as target values.
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Affiliation(s)
- Chin B Eap
- Unit of Biochemistry and Clinical Psychopharmacology, University Department of Adult Psychiatry, Cery Hospital, Prilly-Lausanne, Switzerland.
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Farney RJ, Walker JM, Cloward TV, Rhondeau S. Sleep-disordered breathing associated with long-term opioid therapy. Chest 2003; 123:632-9. [PMID: 12576394 DOI: 10.1378/chest.123.2.632] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Three patients are described who illustrate distinctive patterns of sleep-disordered breathing that we have observed in patients who are receiving long-term, sustained-release opioid medications. Polysomnography shows respiratory disturbances occur predominantly during non-rapid eye movement (NREM) sleep and are characterized by ataxic breathing, central apneas, sustained hypoxemia, and unusually prolonged obstructive "hypopneas" secondary to delayed arousal responses. In contrast to what is usually observed in subjects with obstructive sleep apnea (OSA), oxygen desaturation is more severe and respiratory disturbances are longer during NREM sleep compared to rapid eye movement sleep. Further studies are needed regarding the effects of opioids on respiration during sleep as well as the importance of interaction with other medications and associated risk factors for OSA.
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Affiliation(s)
- Robert J Farney
- Intermountain Sleep Disorders Center, LDS Hospital, Salt Lake City, UT 84143, USA.
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Eap CB, Lessard E, Baumann P, Brawand-Amey M, Yessine MA, O'Hara G, Turgeon J. Role of CYP2D6 in the stereoselective disposition of venlafaxine in humans. PHARMACOGENETICS 2003; 13:39-47. [PMID: 12544511 DOI: 10.1097/00008571-200301000-00006] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
CYP2D6 is involved in the O-demethylation metabolic pathway of venlafaxine in humans. In this study, we investigated whether this isozyme is stereoselective. Plasma samples from seven CYP2D6 extensive metabolizers (EMs) and five CYP2D6 poor metabolizers (PMs), collected during a period without and with coadministration of quinidine, were analysed. Subjects were administered venlafaxine hydrochloride 18.75 mg orally every 12 h for 48 h on two occasions (1 week apart); once alone and once during the concomitant administration of quinidine sulphate every 12 h. Blood and urine samples were collected under steady-state conditions over one dosing interval (12 h). The present results show that, although CYP2D6 catalyses the O-demethylation of both enantiomers of venlafaxine, it displays a marked stereoselectivity towards the (R)-enantiomer. The oral clearance of (R)-venlafaxine was found to be nine-fold higher in EMs compared to PMs [median (range) 173 (29-611) l/h versus 20 (16-24) l/h, P < 0.005], while it was two-fold higher for (S)-venlafaxine [73 (32-130) l/h versus 37 (21-44) l/h, P < 0.05]. In EMs, quinidine decreased (R)- and (S)-venlafaxine oral clearance by 12-fold ( 0.05) and four-fold ( 0.05), respectively. In contrast, quinidine did not have any effects on renal clearance of (R)-venlafaxine [4 (2-10) l/h for venlafaxine alone versus 5 (0.6-7) l/h for venlafaxine + quinidine] and of (S)-venlafaxine [4 (1-7) l/h for venlafaxine alone versus 3 (0.4-6) l/h for venlafaxine + quinidine]. The coadministration of quinidine to EMs resulted in an almost complete inhibition of the partial metabolic clearance of (R)-venlafaxine to O-demethylated metabolites [127 (10-493) l/h down to 1 (0.1-3) l/h, 0.05], while a seven-fold reduction was measured for (S)-venlafaxine [47 (14-94) l/h versus 7 (1-19) l/h, 0.05]. In PMs, coadministration of quinidine did not significantly change oral clearance and partial metabolic clearance of (R)- and (S)-venlafaxine to its various metabolites. In contrast, data obtained on the partial metabolic clearance of (R)- and (S)-venlafaxine to N-demethylated metabolites, a reaction which is mediated by CYP3A4, suggest a lack of stereoselectivity of this enzyme.
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Affiliation(s)
- Chin B Eap
- Unité de Biochimie et Psychopharmacologie Clinique, Département Universitaire de Psychiatrie Adulte, Hôpital de Cery, Lausanne, Switzerland.
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Fishman SM, Wilsey B, Mahajan G, Molina P. Methadone Reincarnated: Novel Clinical Applications with Related Concerns. PAIN MEDICINE 2002; 3:339-48. [PMID: 15099239 DOI: 10.1046/j.1526-4637.2002.02047.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Methadone has numerous advantages as an analgesic, which have supported its recent increase in use. However, methadone also has a pharmacological profile as an opioid that differentiates it from other, better known or more widely used opioids. It also has unusual pharmacodynamics, pharmacokinetics, and metabolism that must be considered for safe use of methadone as an analgesic. This review looks at the history of methadone use as an analgesic and its properties that distinguish it as an unusual, and potentially, unstable opioid.
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Affiliation(s)
- Scott M Fishman
- Division of Pain Medicine, Department of Anesthesiology and Pain Medicine, University of California, Davis 95817, USA.
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Begré S, von Bardeleben U, Ladewig D, Jaquet-Rochat S, Cosendai-Savary L, Golay KP, Kosel M, Baumann P, Eap CB. Paroxetine increases steady-state concentrations of (R)-methadone in CYP2D6 extensive but not poor metabolizers. J Clin Psychopharmacol 2002; 22:211-5. [PMID: 11910269 DOI: 10.1097/00004714-200204000-00017] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Steady-state blood concentrations of (R)- methadone (i.e., the active form), (S)-methadone, and (R,S)-methadone were measured before and after introduction of paroxetine 20 mg/day during a mean period of 12 days in 10 addict patients in methadone maintenance treatment. Eight patients were genotyped as CYP2D6 homozygous extensive metabolizers (EMs) and two patients as poor metabolizers (PMs). Paroxetine significantly increased concentrations of both enantiomers of methadone in the whole group (mean increase for (R)-methadone +/- SD, 26 +/- 32%; range, -14% to +83%, p = 0.032; for (S)-methadone, 49 +/- 51%; range, -29% to +137%, p = 0.028; for (R,S)-methadone, 35 +/- 41%; range, -20% to +112%, p = 0.032) and in the group of eight EMs (mean increase, 32%, p = 0.036; 53%, p = 0.028; and 42%, p = 0.036, for (R)-methadone, (S)-methadone, and (R,S)-methadone, respectively). On the other hand, in the two PMs, (S)-methadone but not (R)-methadone concentrations were increased by paroxetine (mean increases of 36% and 3%, respectively). Paroxetine is a strong CYP2D6 inhibitor, and these results confirm previous studies showing an involvement of CYP2D6 in methadone metabolism with a stereoselectivity toward the (R)-enantiomer. Because paroxetine is a mild inhibitor of CYP1A2, CYP2C9, CYP2C19, and CYP3A4, increase of (S)-methadone concentrations in both EMs and PMs could be mediated by inhibition of any of these isozymes.
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Affiliation(s)
- Stefan Begré
- Psychiatrische Universitätsklinik Basel, Basel, Switzerland
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Abstract
A 60-year-old man with advanced gastric cancer achieved good pain control on a stable dose of methadone for 10 days. However, he developed respiratory depression 2 days after intravenous fluconazole was administrated for refractory oral candidiasis. Intravenous naloxone effectively reversed the respiratory depression. This case illustrates a significant interaction between methadone and fluconazole, and highlights the need for awareness of potential interactions between drugs used in palliative care.
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Affiliation(s)
- Yoko Tarumi
- Palliative Care Program, Grey Nuns Community Hospital, Edmonton, Alberta, Canada
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Gex-Fabry M, Balant-Gorgia AE, Balant LP. Therapeutic drug monitoring databases for postmarketing surveillance of drug-drug interactions. Drug Saf 2002; 24:947-59. [PMID: 11735651 DOI: 10.2165/00002018-200124130-00002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Drug-drug interactions can be associated with patient morbidity due to either increased toxicity or a potentially ineffective concentration. Because interactions cannot always be anticipated during drug development and actual patients receiving a drug for therapeutic use often differ from those included in clinical trials, postmarketing surveillance is essential. Therapeutic drug monitoring (TDM) databases offer a unique opportunity in this respect. Prerequisites for TDM databases to provide valid information in a pharmacoepidemiological perspective include the following: precise description of exposure to the potentially interacting drugs; measurement of parent compound and active metabolites through accurate and precise analytical techniques; documentation of relevant patient characteristics that may act as confounding factors (e.g. gender, age, smoking habits); repeated assessments over time if possible; and sound pharmacokinetic framework for data selection, analysis and interpretation. The contribution of TDM to the documentation of drug-drug interactions takes advantage of different possible study designs, discussed on the basis of recently published studies. The single case report plays an important role as an alert signal. It is illustrated for a patient on long-term treatment, who displayed an unexpectedly high clozapine concentration after the introduction of ciprofloxacin comedication. The prospective on and off comedication panel study shows advantages in terms of carefully selected inclusion criteria and control of treatment modalities. A study of the thioridazine-fluvoxamine interaction is presented, with patients followed on thioridazine monotherapy, after introduction of fluvoxamine and after its discontinuation. The main advantage of the retrospective large-scale TDM database screen is representativeness of patients actually treated, whereas drawbacks are related to quality of data and suitability for valid interpretation. Such an approach is illustrated by a review of data collected over 10 years of routine TDM that allowed documenting induction of nortriptyline metabolism by carbamazepine and inhibition by several phenothiazines. Finally, population pharmacokinetics is well suited to observational data collected for TDM purpose, provided quality is ascertained. Focus is placed on interindividual variability and relationship between pharmacokinetic parameters and patient characteristics, including comedication. The population approach is discussed with respect to a study that documented a 32% increase of haloperidol clearance associated with anticonvulsant comedication, in addition to effects of age and bodyweight. Among factors to consider for improved effectiveness in the use of TDM databases for postmarketing surveillance of drug-drug interactions, integration of efficacy and safety data in future studies and communication of expert recommendations to prescribing physicians are essential.
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Affiliation(s)
- M Gex-Fabry
- Clinical Research Unit, Department of Psychiatry, Geneva University Hospitals, Geneva, Switzerland.
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Abstract
AIM: To study the influence of inducers of drug metabolism enzyme, β-naphthoflavone (BNF) and dexamethasone (DEX), on the stereoselective metabolism of propafenone in the rat hepatic microsomes.
METHODS: Phase I metabolism of propafenone was studied using the microsomes induced by BNF and DEX and the non-induced microsome was used as the control. The enzymatic kinetics parameters of propafenone enantiomers were calculated by regress analysis of Eadie-Hofstee Plots. Propafenone enantiomer concentrations were assayed by a chiral HPLC.
RESULTS: The metabolite of propafenone, N-desalkylpropafenone, was found after incubation of propafenone with the rat hepatic microsomes induced by BNF and DEX. In these two groups, the stereoselectivity favoring R (-) isomer was observed in metabolism at low substrate concentrations of racemic propafenone, but lost the stereoselectivity at high substrate concentrations. However, in control group, no stereoselectivity was observed. The enzyme kinetic parameters were: ① Km. Control group: R (-) 83 ± 6, S (+) 94 ± 7; BNF group: R (-) 105 ± 6, S (+) 128 ± 14; DEX group: R (-) 86 ± 11, S (+) 118 ± 16; ② υmax. Control group: R (-) 0.75 ± 0.16, S (+) 0.72 ± 0.07; BNF group: R (-)1.04 ± 0.15, S (+)1.0 7 ± 14; DEX group: R (-) 0.93 ± 0.06, S (+) 1.04 ± 0.09; ③ Clint. Control group: R (-) 8.9 ± 1.1, S (+) 7.6 ± 0.7; BNF group: R (-)9.9 ± 0.9, S (+)8.3 ± 0.7; DEX group: R (-) 10.9 ± 0.8, S (+) 8.9 ± 0.9. The enantiomeric differences in Km and Clint were both significant, but not in υmax, in BNF and DEX group. Whereas enantiomeric differences in three parameters were all insignificant in control group. Furthermore, Km and υ max were both significantly less than those in BNF or DEX group. In the rat liver microsome in duced by DEX, nimodipine (NDP) decreased the stereoselectivity in propafenone metabolism at low substrate concentration. The inhibition of NDP on the metabolism of propafenone was stereo selective with R (-)-isomer being impaired more than S (+)-isomer. The inhibition constant (Ki) of S (+)- and R (-)-propafenone, calculated from Dixon plots, was 15.4 and 8.6 mg•L¯¹, respectively.
CONCLUSION: CYP1A subfamily (induced by BNF) and CYP3A4 (induced by DEX) have pronounced contribution to propafenone N-desalkylation which exhibited stereose lectivity depending on substrate concentration. The molecular base for this phenomenon is the stereo selectivity in affinity of substrate to the enzyme activity centers instead of at the catalyzing sites.
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Affiliation(s)
- Q Zhou
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang Province, China
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Moolchan ET, Umbricht A, Epstein D. Therapeutic drug monitoring in methadone maintenance: choosing a matrix. J Addict Dis 2001; 20:55-73. [PMID: 11318398 DOI: 10.1300/j069v20n02_05] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Methadone maintenance is the premier pharmacological treatment for opioid addiction, but it is rarely informed by evidence-based practice guidelines for dosage monitoring and adjustment. Such guidelines are crucial because the pharmacokinetics of methadone vary greatly among patients, and this variation may account for differences in treatment outcome. We review the pharmacokinetics of methadone and factors that may alter it (including drug interactions, disease states, and idiosyncratic differences among patients). Also reviewed are prospects for therapeutic drug monitoring (TDM) of methadone in plasma, urine, sweat, and saliva. Due to its ease of collection and its presumed representation of the bioavailable free-fraction of methadone, saliva may be a promising matrix. However, saliva methadone concentrations are influenced by salivary pH, and future studies are needed to determine how to control for that. Administrative, medical, and social implications of methadone TDM are briefly discussed.
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Affiliation(s)
- E T Moolchan
- Department of Health and Human Services, National Institute of Health, National Institute of Drug Abuse, Baltimore, MD 21224, USA.
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Robles E, Miller FB, Gilmore-Thomas KK, McMillan DE. Implementation of a clinic policy of client-regulated methadone dosing. J Subst Abuse Treat 2001; 20:225-30; discussion 231. [PMID: 11516591 DOI: 10.1016/s0740-5472(00)00168-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A six-month interval (baseline) during which methadone doses above 99 mg required individual approval by the clinic's physician was compared with the subsequent 16-month period in which a policy of patient-regulated methadone dosing with no preset upper limit was implemented. During the later phase, all patients were required to remain at each selected dose for a minimum of four days, and standard compliance-based take-home dosing procedures were followed. For patients in the study sample (n=57), the daily maximum methadone dose increased from 165 mg during baseline to 300 mg during the self-regulation period, while their average daily methadone dose increased from 76.84 mg to 80.04 mg (W=473, n=57, p=0.01). Monthly percent of opiate-positive urine specimens decreased significantly from 5.26% during baseline to 1.64% during the self-regulated dose period (W=169, n=57, p<0.01), and use of other drugs remained unchanged. No patient failed to show possession of recalled take-home doses, and no instances of liquid methadone diversion were reported by law enforcement agencies in the area.
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Affiliation(s)
- E Robles
- Department of Pharmacology and Toxicology, Substance Abuse Treatment Clinic, University of Arkansas for Medical Sciences, 4301 West Markham St., Slot 611-1, Little Rock, AR 72205-7199, USA.
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Boulton DW, Arnaud P, DeVane CL. A single dose of methadone inhibits cytochrome P-4503A activity in healthy volunteers as assessed by the urinary cortisol ratio. Br J Clin Pharmacol 2001; 51:350-4. [PMID: 11318772 PMCID: PMC2014462 DOI: 10.1046/j.1365-2125.2001.01360.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2000] [Accepted: 12/12/2000] [Indexed: 12/26/2022] Open
Abstract
AIMS To examine the effect of a single oral dose of methadone on cytochrome P450 (CYP) 3A activity using the urinary 6beta-hydroxycortisol to cortisol ratio (UCR) as a marker of CYP3A activity. METHODS A single oral dose (0.2 mg kg-1) of rac-methadone was administered to eight healthy female volunteers. Frequent blood samples and all urine over seven time periods was collected for 96 h following dosing. The UCR and the concentration of the major CYP3A metabolite of methadone, EDDP, were measured in urine. Methadone enantiomer concentrations were determined in plasma and urine. All quantifications were performed by validated high performance liquid chromatography assays. RESULTS In all volunteers a significant decline of the UCR from immediately predose values was observed at the 4-8 and 8-12 h collection periods (P < 0.05, 95% CI for the differences: 0.4,16 and 0.6,16, respectively) with a return to immediately predose values after 2-3 days, suggesting methadone was an inhibitor of CYP3A. The UCR was found to be significantly correlated with the amount of EDDP excreted in the urine and with the area under the plasma concentration vs time profile for total (R + S) methadone, supporting in vitro data that CYP3A is primarily responsible for EDDP formation and has a significant influence on methadone disposition. CONCLUSIONS Methadone appears to be a CYP3A inhibitor in vivo following a single oral dose and measurements of the urinary cortisol ratio appear to be a useful index to follow this inhibition.
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Affiliation(s)
- D W Boulton
- Laboratory of Drug Disposition and Pharmacogenetics, Department of Psychiatry and Behavioural Sciences and Department of Microbiology and Immunology, Medical University of South Carolina, Charleston 29425, USA
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Eap CB, Broly F, Mino A, Hämmig R, Déglon JJ, Uehlinger C, Meili D, Chevalley AF, Bertschy G, Zullino D, Kosel M, Preisig M, Baumann P. Cytochrome P450 2D6 genotype and methadone steady-state concentrations. J Clin Psychopharmacol 2001; 21:229-34. [PMID: 11270921 DOI: 10.1097/00004714-200104000-00016] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A genetic polymorphism of cytochrome P450 2D6 has been described with the existence of poor (zero functional genes), extensive (one or two functional genes), and ultrarapid metabolizers (three or more functional genes). The authors measured the steady-state trough (R)- (i.e., the active enantiomer), (S)-, and (R,S)-methadone plasma levels in opiate-dependent patients receiving methadone maintenance treatment (MMT) and genotyped them for cytochrome P4502D6. The patients' medical records were reviewed to assess the outcome of the MMT with regard to the absence of illicit opiate consumption and to the absence of withdrawal complaints in ultrarapid and poor metabolizers. Of 256 patients included, 18 were found to be poor metabolizers, 228 to be extensive metabolizers, and 10 to be ultrarapid metabolizers. Significant differences were found between genotypes for (R)- (p = 0.024), (S)- (p = 0.033), and (R,S)-methadone (p = 0.026) concentrations to dose-to-weight ratios. For (R)-methadone, a significant difference was found between ultrarapid metabolizers and poor metabolizers (p = 0.009), with the median value in the former group being only 54% of the median value in the latter group. These results confirm the involvement of cytochrome P450 2D6 in methadone metabolism. Although the difference was nonsignificant (p = 0.103), 13 (72%) of the 18 poor metabolizers and only 4 (40%) of the 10 ultrarapid metabolizers were considered successful in their treatment. More studies are needed to examine the influence of the ultrarapid metabolizer status on the outcome of the MMT.
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Affiliation(s)
- C B Eap
- Département Universitaire de Psychiatrie Adulte, H pital de Cery, Prilly-Lausanne, Switzerland.
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47
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Eap CB, Bourquin M, Martin J, Spagnoli J, Livoti S, Powell K, Baumann P, Déglon J. Plasma concentrations of the enantiomers of methadone and therapeutic response in methadone maintenance treatment. Drug Alcohol Depend 2000; 61:47-54. [PMID: 11064183 DOI: 10.1016/s0376-8716(00)00121-6] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Methadone is a 50:50 mixture of two enantiomers and (R)-methadone accounts for the majority of its opioid effect. The aim of this study was to determine whether a blood concentration of (R)-methadone can be associated with therapeutic response in addict patients in methadone maintenance treatment. Trough plasma concentrations of (R)-, (S)- and (R,S)-methadone were measured in 180 patients in maintenance treatment. Therapeutic response was defined by the absence of illicit opiate or cocaine in urine samples collected during a 2-month period prior to blood sampling. A large interindividual variability of (R)-methadone concentration-to-dose-to-weight ratios was found (mean, S.D., median, range: 112, 54, 100, 19-316 ng x kg/ml x mg). With regard to the consumption of illicit opiate (but not of cocaine), a therapeutic response was associated with (R)- (at 250 ng/ml) and (R,S)-methadone (at 400 ng/ml) but not with (S)-methadone concentrations. A higher specificity was calculated for (R)- than for (R,S)-methadone, as the number of non-responders above this threshold divided by the total number of non-responders was higher for (R,S)-methadone (19%) than for (R)-methadone (7%). The results support the use of therapeutic drug monitoring of (R)-methadone in cases of continued intake of illicit opiates. Due to the variability of methadone concentration-to-dose-to-weight ratios, theoretical doses of racemic methadone could be as small as 55 mg/day and as large as 921 mg/day to produce a plasma (R)-methadone concentration of 250 ng/ml in a 70-kg patient. This demonstrates the importance of individualizing methadone treatment.
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Affiliation(s)
- C B Eap
- Unité de Biochimie et Psychopharmacologie Clinique, Département Universitaire de Psychiatrie Adulte, Hôpital de Cery, CH-1008, Prilly-Lausanne, Switzerland.
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48
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Abstract
Ciprofloxacin, given to a patient successfully treated with methadone for more than 6 years, caused profound sedation, confusion, and respiratory depression. We suggest that this was caused by ciprofloxacin inhibition of CYP1A2 and CYP3A4 activity, two of the cytochrome p450 isozymes involved in the metabolism of methadone.
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Rudaz S, Ortelli D, Gex-Fabry M, Déglon JJ, Balant L, Veuthey JL. Development of validated stereoselective methods for methadone determination in clinical samples. Chirality 1999; 11:487-94. [PMID: 10419284 DOI: 10.1002/(sici)1520-636x(1999)11:5/6<487::aid-chir22>3.0.co;2-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A stereoselective analysis of methadone (Mtd) in whole blood and serum was developed using liquid chromatography on a protein based chiral stationary phase. Liquid-liquid extraction (LLE) and solid phase extraction methods were applied before chromatographic analysis. The extraction procedure, as well as the choice of the biological matrix, showed significant differences in the extraction yield and in the precision of the assays. Serum was selected for this assay and LLE was chosen as the preparation step because of its simplicity and rapidity. The total procedure was validated and applied to clinical samples. Samples taken from 45 heroin-addicted patients were analyzed. A correlation was found between the dose administered and Mtd concentration (total and R-form), but interindividual variability of the total normalized Mtd was seen (concentration varied from 90 to 530 ng/ml). Furthermore, two populations were apparently observed with a mean Mtd concentration of 200 and 475 ng/ml, respectively. Stereoselective analyses showed that more than 50% of the patients presented a nonracemic ratio, and particularly about 25% showed a preferential metabolism of the active R-Mtd enantiomer. Therefore, the stereoselective determination of Mtd is necessary to improve the quality of the treatment of heroin addiction.
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Affiliation(s)
- S Rudaz
- Laboratory of Pharmaceutical Analytical Chemistry, University of Geneva, Switzerland
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50
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Rostami-Hodjegan A, Wolff K, Hay AW, Raistrick D, Calvert R, Tucker GT. Population pharmacokinetics of methadone in opiate users: characterization of time-dependent changes. Br J Clin Pharmacol 1999; 48:43-52. [PMID: 10383559 PMCID: PMC2014882 DOI: 10.1046/j.1365-2125.1999.00974.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/1998] [Accepted: 03/12/1999] [Indexed: 11/20/2022] Open
Abstract
AIMS Although methadone is widely used to treat opiate dependence, guidelines for its dosage are poorly defined. There is increasing evidence to suggest that a strategy based on plasma drug monitoring may be useful to detect non-compliance. Therefore, we have developed a population-based pharmacokinetic (POP-PK) model that characterises adaptive changes in methadone kinetics. METHODS Sparse plasma rac-methadone concentrations measured in 35 opiate-users were assessed using the P-Pharm software. The final structural model comprised a biexponential function with first-order input and allowance for time-dependent change in both clearance (CL) and initial volume of distribution (V ). Values of these parameters were allowed to increase or decrease exponentially to an asymptotic value. RESULTS Increase in individual values of CL and increase or decrease in individual values of V with time was observed in applying the model to the experimental data. CONCLUSIONS A time-dependent increase in the clearance of methadone is consistent with auto-induction of CYP3A4, the enzyme responsible for much of the metabolism of the drug. The changes in V with time might reflect both up- and down-regulation of alpha1-acid glycoprotein, the major plasma binding site for methadone. By accounting for adaptive kinetic changes, the POP-PK model provides an improved basis for forecasting plasma methadone concentrations to predict and adjust dosage of the drug and to monitor compliance in opiate-users on maintenance treatment.
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Affiliation(s)
- A Rostami-Hodjegan
- University of Sheffield, Section of Molecular Pharmacology and Pharmacogenetics, Division of Clinical Sciences, The Royal Hallamshire Hospital, Sheffield
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