Methadone and fluconazole: respiratory depression by drug interaction

Population Pharmacokinetics of Methadone after Oral Administration in Japanese Patients with Cancer-Related Pain

Methadone tablets were approved for use in Japan in March 2013. The metabolism of methadone is complex and executed mainly by the cytochromes, CYP3A4 and CYP2B6. The aim of this study was to evaluate the pharmacokinetics of methadone upon oral administration in Japanese patients who experienced cancer-related pain. The concentration of the drug in blood samples was measured in 25 patients undergoing methadone therapy, and the factors leading to variations were investigated. A population pharmacokinetic analysis was evaluated using the Phoenix® NLME^TM software. Based on this, the ALBI (albumin-bilirubin) score was identified as a significant factor that could be used to assess variations in the serum concentration of methadone, which was then incorporated into the following final model formula: clearance (L/h) = 5.38 × (ALBI score/-2.139)^1.88. The results of these pharmacokinetic parameters suggested that, in clinical use, the dose of methadone should be reduced if liver function declined in patients with cancer-related pain.

Concomitant Filled Prescriptions of Oxymorphone or Oxycodone with CYP3A Inhibitors and Inducers

BACKGROUND

Oxymorphone's metabolism does not involve the hepatic cytochrome P450 (CYP) system. The effect of this pharmacokinetic feature of oxymorphone on opioid prescribing is unknown.

OBJECTIVE

To assess the relative frequency with which oxymorphone and oxycodone (a CYP3A-metabolized opioid analgesic) were each prescribed to patients concomitantly receiving CYP3A-modifying drugs (i.e., inducers and inhibitors) to characterize opioid-prescribing patterns in patients at risk for CYP3A-related drug interactions.

METHODS

We analyzed the Sentinel Distributed Database from January 1, 2013, to December 31, 2016, to identify the proportion of patients with concomitant dispensing of selected CYP3A modifiers among initiators of oxymorphone. We then repeated the analysis using oxycodone instead of oxymorphone. We conducted sensitivity analyses that varied the washout periods for each opioid to account for potential opioid switching.

RESULTS

In the primary analysis, the proportion of patients with concomitant incident dispensings of oxymorphone and selected CYP3A modifiers was 3.26% (95% CI = 3.09%-3.43%), and the proportion of patients with incident dispensings of oxycodone and selected CYP3A modifiers was 2.82% (95% CI = 2.79%-2.85%). The difference between proportions was 0.43% (95% CI = 0.26%-0.60%). Sensitivity analyses that varied the washout periods for each opioid with respect to the other opioid to account for switching yielded similar results.

CONCLUSIONS

We observed similar proportions of patients using selected CYP3A modifiers concomitantly with both oxymorphone and oxycodone. While the CIs of the point estimates did not overlap, the absolute differences between the proportions were small.

DISCLOSURES

This project was supported by Task Order HHSF22301001T under Master Agreement HHSF223201400030I from the U.S. Food and Drug Administration (FDA). The FDA approved the study protocol, including the statistical analysis plan, and reviewed and approved the manuscript. Coauthors from the FDA participated in the results interpretation and in the preparation and decision to submit the manuscript for publication. Coyle, Money, Staffa, Meyer, and Woods are employed by the FDA. The other authors have no financial conflicts of interest to report. The views expressed are those of the authors and not necessarily those of the U.S. Department of Health and Human Services, U.S. Food and Drug Administration.

Methadone against cancer: Lost in translation

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.

Pain management in trauma: A review study

Background:

Pain in trauma has a role similar to the double-edged sword. On the one hand, pain is a good indicator to determine the severity and type of injury. On the other hand, pain can induce sever complications and it may lead to further deterioration of the patient. Therefore, knowing how to manage pain in trauma patients is an important part of systemic approach in trauma. The aim of this manuscript is to provide information about pain management in trauma in the Emergency Room settings.

Methods:

In this review we searched among electronic and manual documents covering a 15-yr period between 2000 and 2016. Our electronic search included Pub Med, Google scholar, Web of Science, and Cochrane databases. We looked for articles in English and in peer-reviewed journals using the following keywords: acute pain management, trauma, emergency room and injury.

Results:

More than 3200 documents were identified. After screening based on the study inclusion criteria, 560 studies that had direct linkage to the study aim were considered for evaluation based World Health Organization (WHO) pain ladder chart.

Conclusions:

To provide adequate pain management in trauma patients require: adequate assessment of age-specific pharmacologic pain management; identification of adequate analgesic to relieve moderate to severe pain; cognizance of serious adverse effects of pain medications and weighting medications against their benefits, and regularly reassessing patients and reevaluating their pain management regimen. Patient-centered trauma care will also require having knowledge of barriers to pain management and discussing them with the patient and his/her family to identify solutions.

Drug-induced neurotoxicity in addiction medicine: From prevention to harm reduction

Neurotoxicity is considered as a major cause of neurodegenerative disorders. Most drugs of abuse have nonnegligible neurotoxic effects many of which are primarily mediated by several dopaminergic and glutamatergic neurotransmitter systems. Although many researchers have investigated the medical and cognitive consequences of drug abuse, the neurotoxicity induced by these drugs still requires comprehensive attention. The science of neurotoxicity promises to improve preventive and therapeutic strategies for brain disorders such as Alzheimer disease and Parkinson's disease. However, its clinical applications for addiction medicine remain to be defined adequately. This chapter reviews the most commonly discussed mechanisms underlying neurotoxicity induced by common drugs of abuse including amphetamines, cocaine, opiates, and alcohol. In addition, the known factors that trigger and/or predispose to drug-induced neurotoxicity are discussed. These factors include drug-related, individual-related, and environmental insults. Moreover, we introduce some of the potential pharmacological antineurotoxic interventions deduced from experimental animal studies. These interventions involve various targets such as dopaminergic system, mitochondria, cell death signaling, and NMDA receptors, among others. We conclude the chapter with a discussion of addicted patients who might benefit from such interventions.

Clinically significant drug-drug interactions involving opioid analgesics used for pain treatment in patients with cancer: a systematic review

BACKGROUND

Opioids are the most frequently used drugs to treat pain in cancer patients. In some patients, however, opioids can cause adverse effects and drug-drug interactions. No advice concerning the combination of opioids and other drugs is given in the current European guidelines.

OBJECTIVE

To identify studies that report clinically significant drug-drug interactions involving opioids used for pain treatment in adult cancer patients.

DESIGN AND DATA SOURCES

Systematic review with searches in Embase, MEDLINE, and Cochrane Central Register of Controlled Trials from the start of the databases (Embase from 1980) through January 2014. In addition, reference lists of relevant full-text papers were hand-searched.

RESULTS

Of 901 retrieved papers, 112 were considered as potentially eligible. After full-text reading, 17 were included in the final analysis, together with 15 papers identified through hand-searching of reference lists. All of the 32 included publications were case reports or case series. Clinical manifestations of drug-drug interactions involving opioids were grouped as follows: 1) sedation and respiratory depression, 2) other central nervous system symptoms, 3) impairment of pain control and/or opioid withdrawal, and 4) other symptoms. The most common mechanisms eliciting drug-drug interactions were alteration of opioid metabolism by inhibiting the activity of cytochrome P450 3A4 and pharmacodynamic interactions due to the combined effect on opioid, dopaminergic, cholinergic, and serotonergic activity in the central nervous system.

CONCLUSION

Evidence for drug-drug interactions associated with opioids used for pain treatment in cancer patients is very limited. Still, the cases identified in this systematic review give some important suggestions for clinical practice. Physicians prescribing opioids should recognize the risk of drug-drug interactions and if possible avoid polypharmacy.

Use of naloxone for reversal of life-threatening opioid toxicity in cancer-related pain

Objective

To review the emergency-based approach to opioid toxicity reversal in cancer-related pain patients.

Data source

A MEDLINE and PubMed search was conducted (1966 to May 2014) using the terms opioids, cancer, naloxone, respiratory depression, morphine, morphine derivatives, emergency, and anaphylaxis.

Methods of study selection

English articles in human subjects identified from the MEDLINE and PubMed search were evaluated. Citations were excluded if they addressed acute overdoses, non-cancer pain, and/or acute, non-chronic pain.

Data extraction and synthesis

Pain is a common occurrence in the oncology population. Although toxicity from opioids is common, life-threatening toxicities are not. The use of naloxone in this particular patient population occurs frequently for any perceived opioid-related effect and can be detrimental to the oncology patient’s care and quality of life. Difficulties exist when attempting to separate opioid toxicity from disease progression or metastases and, therefore, a thorough history is needed prior to complete opioid reversal in this population. Severity of the opioid intoxication should dictate reversal strategy. Dosing strategies that take into account both the treatment of the opioid-related effects as well as the negative effects reversal will have on the patient are offered. We also review the pre-hospital setting and identified the need for protocols that not only take the patient’s symptoms into account, but also the patient’s cancer history.

Conclusion

Opioid reversal protocols should be developed by a multi-disciplinary team. Each protocol should differentiate those toxicities which are life-threatening and require complete opioid reversal with toxicities that require small aliquots of naloxone to mitigate the presenting symptoms.

Safe methadone induction and stabilization: report of an expert panel

OBJECTIVES

Methadone is a well-studied, safe, and effective medication when dispensed and consumed properly. However, a number of studies have identified elevated rates of overdose and death in patients being treated with methadone for either addiction or chronic pain. Among patients being treated with methadone in federally certified opioid treatment programs, deaths most often occur during the induction and stabilization phases of treatment. To address this issue, the federal Substance Abuse and Mental Health Services Administration invited the American Society of Addiction Medicine to convene an expert panel to develop a consensus statement on methadone induction and stabilization, with recommendations to reduce the risk of patient overdose or death related to methadone maintenance treatment of addiction.

METHODS

A comprehensive literature search of English-language publications (1979-2011) was conducted via MEDLINE and EMBASE. Methadone Action Group members evaluated the resulting information and collaborated in formulating the consensus statement presented here, which subsequently was reviewed by more than 100 experts in the field.

RESULTS

Published data indicate that deaths during methadone induction occur because the initial dose is too high, the dose is increased too rapidly, or the prescribed methadone interacts with another drug. Therefore, the Methadone Action Group has developed recommendations to help methadone providers avoid or minimize these risks.

CONCLUSIONS

Careful management of methadone induction and stabilization, coupled with patient education and increased clinical vigilance, can save lives in this vulnerable patient population.

Prevalence of potential drug-drug interactions in cancer patients treated with oral anticancer drugs

BACKGROUND

Potential drug-drug interactions (PDDIs) in patients with cancer are common, but have not previously been quantified for oral anticancer treatment. We assessed the prevalence and seriousness of potential PDDIs among ambulatory cancer patients on oral anticancer treatment.

METHODS

A search was conducted in a computer-based medication prescription system for dispensing oral anticancer drugs to outpatients in three Dutch centres. Potential drug-drug interactions were identified using electronic (Drug Interaction Fact software) and manual screening methods (peer-reviewed reports).

RESULTS

In the 898 patients included in the study, 1359 PDDIs were identified in 426 patients (46%, 95% confidence interval (CI)=42-50%). In 143 patients (16%), a major PDDI was identified. The drug classes most frequently involved in a major PDDI were coumarins and opioids. The majority of cases concerned central nervous system interactions, PDDIs that can cause gastrointestinal toxicity and prolongation of QT intervals. In multivariate analysis, concomitant use of more drugs (odds ratio (OR)=1.66, 95% CI=1.54-1.78, P<0001) and genito-urinary cancer (OR=0.25, 95% CI=0.12-0.52, P<0001) were risk factors.

CONCLUSION

Potential drug-drug interactions are very common among cancer patients on oral cancer therapy. Physicians and pharmacists should be more aware of these potential interactions.

Methadone: a review of drug-drug and pathophysiological interactions

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.

Methadone for Cancer Pain

Pain is one of the most common and incapacitating symptoms experienced by patients with advanced cancer. Methadone is a potent opioid with strong affinity for the µ opioid receptor. In addition to being a potent µ opioid receptor ligand, methadone blocks the N-methyl-D-aspartic acid receptor and modulates neurotransmitters involved in descending pain modulation. These 3 properties enhance analgesic activity. Methadone's lack of active metabolites makes it an attractive option when opioid responsiveness declines and renal insufficiency complicates opioid therapy. A lipophilic opioid, methadone can be given by multiple routes. Clinical trial data show equivalence with morphine as an analgesic in moderate to severe cancer pain. Further investigations are needed to define the role of methadone in the management of breakthrough pain and neuropathic pain and to determine whether it is truly superior to morphine, the gold standard of cancer analgesia.

The role of methadone in cancer pain treatment--a review

BACKGROUND

Methadone is an opioid analgesic of step 3 of the World Health Organization (WHO) analgesic ladder.

AIM AND METHODS

To outline pharmacodynamics, pharmacokinetics, drug interactions, equianalgesic dose ratio with other opioids, dosing rules, adverse effects and methadone clinical studies in patients with cancer pain. A review of relevant literature on methadone use in cancer pain was conducted.

RESULTS

Methadone is used in opioid rotation and administered to patients with cancer pain not responsive to morphine or other strong opioids when intractable opioid adverse effects appear. Methadone is considered as the first strong opioid analgesic and in patients with renal impairment. Methadone possesses different pharmacodynamics and pharmacokinetics in comparison to other opioids. The advantages of methadone include multimode analgesic activity, high oral and rectal bioavailability, long lasting analgesia, lack of active metabolites, excretion mainly with faeces, low cost and a weak immunosuppressive effect. The disadvantages include long and changeable plasma half-life, high bound to serum proteins, metabolism through P450 system, numerous drug interactions, lack of clear equianalgesic dose ratio to other opioids, QT interval prolongation, local reactions when administered subcutaneously.

CONCLUSIONS

Methadone is an important opioid analgesic at step 3 of the WHO analgesic ladder. Future controlled studies may focus on establishment of methadone equianalgesic dose ratio with other opioids and its role as the first strong opioid in comparative studies with analgesia, adverse effects and quality of life taken into consideration.

Interindividual variability of methadone response: impact of genetic polymorphism

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.

Actual and potential drug interactions associated with methadone

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.

Methadone-associated long QT syndrome: improving pharmacotherapy for dependence on illegal opioids and lessons learned for pharmacology

Methadone is used as the pharmacologic mainstay for substitution for illegal opiates and as analgesic for chronic or cancer-related pain. Given the benefits of methadone substitution for illicit opioids, the finding of an association between methadone and prolongation of cardiac depolarization (QT prolongation) and torsades de pointes is of great concern. QT prolongation can occur with many drugs and is a potentially lethal adverse drug reaction, necessitating risk monitoring and therapeutic alternatives in some patients. Recent studies suggest that QT prolongation with methadone is context dependent: occurrence is more frequent with high doses of methadone, concomitant administration of CYP3A4 inhibitors, hypokalemia, hepatic failure, administration of other QT prolonging drugs and pre-existing heart disease. The valued benefit of methadone substitution therapy on the one hand and the increased cardiovascular risk in particular situations on the other illustrate the difficulties in dealing with drug-induced QT prolongation in general.

Methadone Induction Doses

PURPOSE

To review the literature on methadone deaths and propose evidence-based dosing guidelines.

METHODS

A literature search was conducted on overdose deaths during the induction phase. Data on methadone deaths from the Ontario coroner's office, as well as prescribing guidelines from different countries and jurisdictions, were reviewed. The information was collectively considered and, using the best available evidence, translated into safe dosing guidelines for methadone induction.

RESULTS

A literature review found high death rates during the methadone induction period. Data from the Ontario coroner's office revealed that of deaths that were felt to be attributable to methadone overdose, the majority occurred in those who had consumed diverted methadone: of those deaths within a registered program, the majority occurred during the initial dosing phase. Despite high death rates during induction onto methadone treatment, many jurisdictions do not have prescribing guidelines that take this evidence into account.

CONCLUSIONS

Safer prescribing guidelines are needed to reduce deaths during induction onto methadone treatment. Recommendations are made for safe methadone induction doses.

Liver enzyme induction and inhibition: implications for anaesthesia

Recent breakthroughs in molecular biology have enabled a reclassification of drug metabolising enzymes based on their amino acid sequence. This has led to a better understanding of drug metabolism and drug interactions. The majority of these drug metabolising enzymes may be either induced or inhibited by drugs or by extraneous substances including foodstuffs, cigarette smoke and environmental pollutants. Virtually all drugs used in anaesthesia are metabolised by either hepatic phase 1 or phase II enzymes. This review considers the classification of drug metabolising enzymes, explains the mechanisms of enzyme induction and inhibition, and also considers how the action of drugs commonly used by anaesthetists, including opioids and neuromuscular blocking drugs, may be altered by this mechanism.

Frequency of potential azole drug-drug interactions and consequences of potential fluconazole drug interactions

PURPOSE

To assess the frequency of potential azole-drug interactions and consequences of interactions between fluconazole and other drugs in routine inpatient care.

METHODS

We performed a retrospective cohort study of hospitalized patients treated for systemic fungal infections with an oral or intravenous azole medication between July 1997 and June 2001 in a tertiary care hospital. We recorded the concomitant use of medications known to interact with azole antifungals and measured the frequency of potential azole drug interactions, which we considered to be present when both drugs were given together. We then performed a chart review on a random sample of admissions in which patients were exposed to a potential moderate or major drug interaction with fluconazole. The list of azole-interacting medications and the severity of interaction were derived from the DRUGDEX System and Drug Interaction Facts.

RESULTS

Among the 4,185 admissions in which azole agents (fluconazole, itraconazole or ketoconazole) were given, 2,941 (70.3%) admissions experienced potential azole-drug interactions, which included 2,716 (92.3%) admissions experiencing potential fluconazole interactions. The most frequent interactions with potential moderate to major severity were co-administration of fluconazole with prednisone (25.3%), midazolam (17.5%), warfarin (14.7%), methylprednisolone (14.1%), cyclosporine (10.7%) and nifedipine (10.1%). Charts were reviewed for 199 admissions in which patients were exposed to potential fluconazole drug interactions. While four adverse drug events (ADEs) caused by fluconazole were found, none was felt to be caused by a drug-drug interaction (DDI), although in one instance fluconazole may have contributed.

CONCLUSIONS

Potential fluconazole drug interactions were very frequent among hospitalized patients on systemic azole antifungal therapy, but they had few apparent clinical consequences.

[Methadone and sleep apnea syndrome]

BACKGROUND

Sleep apnea syndrome occurs when, during sleep, breathing stops for 10 seconds or longer, with an index of 5 times or more an hour. It is clinically characterized by loud snoring at night, continuous or interrupted by pauses followed by loud breathing. Sleep is fitful, broken by arousals, and yields little rest. There is daytime excessive sleepiness with repeated involuntary falling asleep, often unknown by the subject.

CLINICAL DESCRIPTION

In this article, we describe an observation of central sleep apnea syndrome in a female patient receiving an opiate replacement therapy.

METHOD

An analysis of the before and after methadone withdrawal polysomnograhic tracing was done for this patient.

RESULTS

This diagnosis etiology and physiopathology are critically approached. Clinicians should be careful in treating induced sleep disorders in such patients.

CONCLUSION

Prescribing benzodiazepines during an opiate withdrawal of the methadone type is not recommended when central apnea occurs.