Utilization of pharmacogenomics and therapeutic drug monitoring for opioid pain management

Methadone metabolism and cytochrome P450 polymorphisms: a systematic review and meta-analysis

INTRODUCTION

Confusion regarding methadone metabolism exists, hampering optimal clinical use. A systematic review was conducted to assess the impacts of cytochrome P450 (CYP) genetic polymorphisms on methadone outcomes.

METHODS

MEDLINE, EMBASE, Web of Science, PsycINFO, and CENTRAL were searched to identify studies reporting methadone dose-adjusted plasma concentrations, clearance, maintenance dose, or treatment response in relation to CYP polymorphisms in humans. ROBINS-I was used to evaluate risk of bias in included studies. Each outcome was synthesized for each CYP using the ratio of means or odds ratio as the effect size measure.

RESULTS

Ten, two, fourteen, and five studies were included in the meta-analyses of the concentration, clearance, dose, and treatment response, respectively. The CYP2B6 c.516 G>T variant was robustly associated with (S)-methadone concentrations (GT+TTvs.GG: ratio of means (RoM) 1.40, p < 0.01) and clearance (GT+TTvs.GG: RoM 0.65, p < 0.01) but less with (R)- or (R,S)-methadone. The CYP2B6 variant also affected methadone dose for opioid use disorder (GT+TTvs.GG: RoM 0.93, p = 0.04). CYP2C19, CYP2C9, CYP2D6, and CYP3A5 polymorphisms did not influence any of the assessed outcomes.

CONCLUSIONS

CYP2B6 genetics had statistically significant impacts on (S)-methadone and less so on (R)-methadone exposure and clearance and was statistically significantly but not clinically meaningfully associated with dose requirements.

Exogenous Opioids and the Human Endocrine System: An Endocrine Society Scientific Statement

The use and misuse of opioids are a growing global problem. Although the effects of these drugs on the human endocrine system have been studied for decades, attention on their related clinical consequences, particularly on the hypothalamic-pituitary system and bone health, has intensified over recent years. This Statement appraises research data related to the impact of opioids on the gonadal and adrenal function. Whereas hypogonadism is well recognized as a side effect of opioids, the significance of their inhibitory actions on the hypothalamic-pituitary-adrenal system and the occurrence of clinically relevant adrenal insufficiency is not fully elucidated. The often-inconsistent results of studies investigating how opioids affect the secretion of GH, prolactin, arginine vasopressin, and oxytocin are assessed. The accumulating evidence of opioid actions on bone metabolism and their negative sequelae on bone mineral density and risk of fracture are also reviewed. In each section, available data on diagnostic and management approaches for opioid endocrine sequelae are described. This Statement highlights a plethora of gaps in research associated with the effects and clinical consequences of opioids on the endocrine system. It is anticipated that addressing these gaps will improve the care of people using or misusing opioids worldwide. The Statement is not intended to serve as a guideline or dictate treatment decisions.

Opioid Monitoring in Clinical Settings: Strategies and Implications of Tailored Approaches for Therapy

This review emphasises the importance of opioid monitoring in clinical practice and advocates for a personalised approach based on pharmacogenetics. Beyond effectively managing pain, meticulous oversight is required to address concerns about side effects, specially due to opioid-crisis-related abuse and dependence. Various monitoring techniques, along with pharmacogenetic considerations, are critical for personalising treatment and optimising pain relief while reducing misuse and addiction risks. Future perspectives reveal both opportunities and challenges, with advances in analytical technologies holding promise for increasing monitoring efficiency. The integration of pharmacogenetics has the potential to transform pain management by allowing for a precise prediction of drug responses. Nevertheless, challenges such as prominent pharmacogenetic testing and guideline standardisation persist. Collaborative efforts are critical for transforming scientific advances into tangible improvements in patient care. Standardised protocols and interdisciplinary collaboration are required to ensure consistent and evidence-based opioid monitoring. Future research should look into the long-term effects of opioid therapy, as well as the impact of genetic factors on individual responses, to help guide personalised treatment plans and reduce adverse events. Lastly, embracing innovation and collaboration can improve the standard of care in chronic pain management by striking a balance between pain relief and patient safety.

Oxycodone, Morphine, and Fentanyl in Patients With Chronic Pain: Proposal of Dose-Specific Concentration Ranges

BACKGROUND

Interpreting opioid concentrations is challenging because of the lack of reference ranges. Therefore, the authors aimed to propose dose-specific concentration ranges in serum for oxycodone, morphine, and fentanyl in patients with chronic pain, based on concentration measurements from a large number of patients and supported by theoretical pharmacokinetic calculations and previously published concentrations.

METHODS

The opioid concentrations in patients undergoing therapeutic drug monitoring (TDM) for various indications (TDM group) and patients with cancer (cancer group) were investigated. Patients were divided based on the daily opioid doses, and the 10th and 90th percentiles of the concentrations in each dose interval were evaluated. In addition, the expected average serum concentrations were calculated for each dose interval based on published pharmacokinetic data, and a targeted literature search for previously reported dose-specific concentrations was performed.

RESULTS

The opioid concentrations in 1054 patient samples were included: 1004 in the TDM group and 50 in the cancer group. In total, 607 oxycodone, 246 morphine, and 248 fentanyl samples were evaluated. The authors proposed dose-specific concentration ranges based mainly on 10th-90th percentiles of the concentrations measured in patient samples, whereas the calculated average concentrations and previously published concentrations were used to adjust the ranges. In general, results from calculations and concentrations retrieved from previous literature were within the 10th-90th percentiles of concentrations from patient samples. However, the lowest calculated average concentrations of fentanyl and morphine were below the 10th percentiles of patient samples in all dose groups.

CONCLUSIONS

The proposed dose-specific ranges may be useful for interpreting steady-state opioid serum concentrations in clinical and forensic settings.

Pharmacogenetics of pain management in Zimbabwean patients with sickle cell disease

Background: Pain is a common cause of hospitalization in sickle cell disease (SCD) patients. Failure to effectively control pain remains a challenge in patient care. Materials & methods: The authors conducted a cross-sectional study to determine the effect of CYP2D6 and UGT2B7 polymorphisms on pain management in 106 Zimbabwean SCD patients. Participant information was collected on a questionnaire. Genotyping was conducted using the GenoPharm® pharmacogenomics open array panel containing CYP2D6 and UGT genetic variants implicated in opioid response. Results: The reduced function alleles CYP2D6*17 and *29 had high frequencies of 15.9% and 12.9%, respectively. UGT2B7 rs73823859 showed a statistically significant correlation with pain levels (p = 0.0454). Conclusion: This study demonstrated the role of UGT2B7 polymorphism in SCD patient pain management.

Reviewing pharmacogenetics to advance precision medicine for opioids

BACKGROUND

Adequate opioid prescribing is critical for therapeutic success of pain management. Despite the widespread use of opioids, optimized opioid therapy remains unresolved with risk of accidental lethal overdosing. With the emergence of accumulating evidence linking genetic variation to opioid response, pharmacogenetic based treatment recommendations have been proposed.

OBJECTIVE

The aim of this review is to evaluate pharmacogenetic evidence and provide an overview on genes involved in the pharmacokinetics and pharmacodynamics of opioids.

METHODS

For this review, a systematic literature search of published articles was used in PubMed®, with no language restriction and between the time period of January 2000 to December 2020. We reviewed randomized clinical studies, study cohorts and case reports that investigated the influence of genetic variants on selected opioid pharmacokinetics and pharmacodynamics. In addition, we reviewed current CPIC clinical recommendations for pharmacogenetic testing.

RESULTS

Results of this review indicate consistent evidence supporting the association between selected genetic variants of CYP2D6 for opioid metabolism. CPIC guidelines include recommendations that indicate the avoidance of tramadol use, in addition to codeine, in CYP2D6 poor metabolizers and ultrarapid metabolizers, and to monitor intermediate metabolizers for less-than-optimal response. While there is consistent evidence for OPRM1 suggesting increased postoperative morphine dosing requirements in A118G G-allele carriers, the clinical relevance remains limited.

CONCLUSION

There is emerging evidence of clinical relevance of CYP2D6 and, to a lesser extent, OPRM1 polymorphism in personalized opioid drug dosing. As a result, first clinics have started to implement pharmacogenetic guidelines for CYP2D6 and codeine.

Endogenous and iatrogenic sources of variability in response to opioid therapy in Post-Surgical and injured orthopedic patients

BACKGROUND

Hydrocodone is the most prescribed opioid in the US. The objective was to evaluate associations between genetic, intrinsic, and extrinsic patient factors, plasma hydrocodone and metabolites, common side effects, and pain scores in a cohort of orthopedic surgery patients.

METHODS

Data for each patient was collected by review of the electronic hospital record (EHR), and patient interview. Patients were recruited from those with trauma or undergoing scheduled elective surgery for total knee replacement or total hip at the University of Louisville Hospital, Baptist East Hospital, and Jewish Hospital, Louisville, KY. Plasma opiate concentrations and a targeted genotyping panel was performed.

RESULTS

There were statistically significant correlations with daily (p < 0.001) and total dose (p = 0.002) of hydrocodone in hospital and duration of opioid therapy. The length of opioid administration was significantly shorter in CYP2D6 EM/UM versus CYP2D6 PM/IM patients (p = 0.018). Subjects with the OPRM1 c.118G variant were also on opioids longer (p = 0.022). The effect of co-administration of a CYP2D6 inhibitor had a significant effect on the length of opioid therapy (P < 0.001). And not surprisingly the effect of the inhibitor adjusted CYP2D6 phenotype was greater in both the hospital stay period and days of opioid use post hospital discharge (p < 0.001).

CONCLUSIONS

Based on this study, patients should be evaluated for the use of inhibitors of CYP2D6, during hydrocodone therapy can alter the phenotype of the patient (phenocopy) and increase the probability that the patient will be on opioids for longer periods of time.

Opportunities and challenges for nonaddictive interventions in chronic pain

The worlds of chronic pain and addiction continue to intersect too often in many ways. Chronic pain significantly impairs and disrupts the quality of life of millions of people worldwide. Opioids remain the most prescribed pharmacotherapy offered to patients to alleviate chronic pain. The extensive and often unnecessary prescription of opioids has created a surge in the prevalence of opioid use disorders and opioid overdose-related deaths. In this brief review, we aim to provide a bench-to-bedside overview of promising biomarkers, therapeutic targets, and challenges related to treating patients with chronic pain. We hope this review will inspire new opportunities and insights into the development of novel, nonaddictive treatments for chronic pain that will be available to patients in the near future.

Pharmacogenomics in chronic pain therapy: from disease to treatment and challenges for clinical practice

Pharmacogenomics (PGx) has emerged as an encouraging tool in chronic pain therapy. Genetic variations associated with drug effectiveness or adverse reactions (amitriptyline/nortriptyline/codeine/oxycodone/tramadol-CYP2D6, amitriptyline-CYP2C19, carbamazepine-HLA-A, carbamazepine/oxcarbazepine-HLA-B) can be used to guide chronic pain management. Despite this evidence, many obstacles still need to be overcome for the effective clinical implementation of PGx. To translate the pharmacogenetic testing into actionable clinical decisions, the Clinical Pharmacogenetics Implementation Consortium has been developing guidelines for several drug–gene pairs. This review will show the applicability of PGx in chronic pain from disease to treatment; report the drug–gene pairs with strongest evidences in the clinic; and the challenges for the clinical implementation of PGx.

A Single Site Population Study to Investigate CYP2D6 Phenotype of Patients with Persistent Non-Malignant Pain

Background and Objectives: Codeine requires biotransformation by the CYP2D6 enzyme, encoded by the polymorphic CYP2D6 gene, to morphine for therapeutic efficacy. CYP2D6 phenotypes of poor, intermediate, and ultra-rapid metabolisers are at risk of codeine non-response and adverse drug reactions due to altered CYP2D6 function. The aim of this study was to determine whether genotype, inferred phenotype, and urinary and oral fluid codeine O-demethylation metabolites could predict codeine non-response following a short course of codeine. Materials and Methods: There were 131 Caucasians with persistent pain enrolled. Baseline assessments were recorded, prohibited medications ceased, and DNA sampling completed before commencing codeine 30 mg QDS for 5 days. Day 4 urine samples were collected 1–2 h post morning dose for codeine O-demethylation metabolites analysis. Final pain assessments were conducted on day 5. Results: None of the poor, intermediate, ultra-rapid metabolisers and only 24.5% of normal metabolisers responded to codeine. A simple scoring system to predict analgesic response from day 4 urinary metabolites was devised with overall prediction success of 79% (sensitivity 0.8, specificity 0.78) for morphine and 79% (sensitivity 0.76, specificity 0.83) for morphine:creatinine ratio. Conclusions: In conclusion, this study provides tentative evidence that day 4 urinary codeine O-demethylation metabolites could predict non-response following a short course of codeine and could be utilised in the clinical assessment of codeine response at the point of care to improve analgesic efficacy and safety in codeine therapy. We offer a scoring system to predict codeine response from urinary morphine and urinary morphine:creatinine ratio collected on the morning of day 4 of codeine 30 mg QDS, but this requires validation before it could be considered for use to assess codeine response in clinical practice.

CYP2D6 Pharmacogenetics Testing and Post-Cesarean Section Pain Scores-a Preliminary Study

OBJECTIVE

Prospective observational study to analyze CYP2D6 pharmacogenetics in 55 Portuguese adult parturients undergoing elective cesarean section and to investigate the association between CYP2D6 alleles and pain score.

METHODS

DNA was extracted from peripheral blood by standard methods. Genetic analysis included allelic discrimination (CYP2D6*1, *2, *3, *4, *5, *6, *10, *17, and *41) and copy number determination with TaqMan probes by real-time polymerase chain reaction (PCR). Allele duplications were confirmed (long PCR and PCR-restriction fragment length polymorphism). Theoretical metabolic profiles prediction was based on genetic data and activity scores. Association was investigated between genotypes and predicted phenotypes with pain scores. Statistical analysis was performed by using a χ2 test, and significance was set at P < 0.05.

RESULTS

The percentage of poor, intermediate, extensive, and ultrarapid metabolizers found were 9%, 38%, 46%, and 7%, respectively. The results reveal a positive association between alleles *4, *10, and pain.

CONCLUSIONS

A positive association was found between predicted reduced or null activity of CYP2D6 and increased pain. It can be hypothesized that if CYP2D6 activity is reduced, tyramine metabolism will decrease, resulting in reduced formation of endogenous dopamine. Consequently, activation of the signal transduction pathways that controls pain and analgesic effect may be reduced, leading to an increase in pain. Therefore, we would recommend CYP2D6 genotyping to anticipate the needs for analgesia, which will help to adjust opioid dose and maximize clinical efficacy while reducing side effects.

Pharmacogenomics and Patient Treatment Parameters to Opioid Treatment in Chronic Pain: A Focus on Morphine, Oxycodone, Tramadol, and Fentanyl

Objective

Opioids are one of the most commonly prescribed medicines for chronic pain. However, their use for chronic pain has been controversial. The objective of this literature review was to identify the role of genetic polymorphisms on patient treatment parameters (opioid dose requirements, response, and adverse effects) for opioids used in malignant and nonmalignant chronic pain. The opioids that this review focuses on are codeine, morphine, oxycodone, tramadol, and fentanyl.

Method

A literature search of databases Medline and Embase was carried out, and studies up to April 2016 were included in this review. Studies were included based on a combination of key words: chronic pain and related terms, pharmacogenetics and related terms, and opioids and related terms.

Results

Among the 1,408 individual papers retrieved from the search in Medline and Embase, 32 original articles were included in this review, with none related to codeine. The 32 papers reported various study designs, opioids, and polymorphisms being studied for associations with treatment outcomes. This literature review reveals that variants in ABCB1, OPRM1, and COMT have been replicated for opioid dosing and variants in ABCB1 have been replicated for both treatment response and adverse effects.

Conclusions

Currently, there are few validated studies to form a strong evidence base to support pharmacogenomics testing when initiating opioid therapy. However, the field of pharmacogenomics in chronic pain is likely to expand over the coming years, with the increasing number of treatment options available and larger cohorts being assembled in order to identify true associations.

The pharmacogenetics of medications used in general anesthesia

General anesthesia is a state of unconsciousness, amnesia, analgesia and akinesia induced by drugs including opioids, hypnotic-sedative agents, muscle relaxants and antiemetics. Clinical and genetic factors are reported to influence the efficacy and side effects of these agents. Based on the evidence, clinical action is needed to improve clinical outcomes. This review summarizes the latest knowledge with regards to the pharmacogenetics of anesthetics and general anesthesia related complications.

Avoidable drug-gene conflicts and polypharmacy interactions in patients participating in a personalized medicine program

AIM

Determine the ability of a pharmacogenetic service, PRIMER, to identify drug-gene (DGI) and drug-drug interactions (DDI) in patients across multiple conditions. PRIMER consists of patient selection criteria, a gene panel and actionable guidance for DGIs and DDIs.

RESULTS

The average patient was prescribed 12 medications. PRIMER identified significant DGIs in 73% of patients tested, with 43% having more than one DGI. DDIs were found in 87% of patients. The most common actionable DGIs were for opioid, psychotropic and cardiovascular medications.

CONCLUSION

The pairing of patient selection criteria, a multigene panel with evidence-based interpretation and review of DDIs maximizes the patients tested who have actionable benefit and alerts physicians to potentially critical adjustments needed for the patient's medication regimen.

Individualized Hydrocodone Therapy Based on Phenotype, Pharmacogenetics, and Pharmacokinetic Dosing

OBJECTIVES

(1) To quantify hydrocodone (HC) and hydromorphone (HM) metabolite pharmacokinetics with pharmacogenetics in CYP2D6 ultra-rapid metabolizer (UM), extensive metabolizer (EM), and poor metabolizer (PM) metabolizer phenotypes. (2) To develop an HC phenotype-specific dosing strategy for HC that accounts for HM production using clinical pharmacokinetics integrated with pharmacogenetics for patient safety.

SETTING

In silico clinical trial simulation.

PARTICIPANTS

Healthy white men and women without comorbidities or history of opioid, or any other drug or nutraceutical use, age 26.3±5.7 years (mean±SD; range, 19 to 36 y) and weight 71.9±16.8 kg (range, 50 to 108 kg).

MAIN OUTCOME MEASURES

CYP2D6 phenotype-specific HC clinical pharmacokinetic parameter estimates and phenotype-specific percentages of HM formed from HC.

RESULTS

PMs had lower indices of HC disposition compared with UMs and EMs. Clearance was reduced by nearly 60% and the t1/2 was increased by about 68% compared with EMs. The canonical order for HC clearance was UM>EM>PM. HC elimination mainly by the liver, represented by ke, was reduced about 70% in PM. However, HC's apparent Vd was not significantly different among UMs, EMs, and PM. The canonical order of predicted plasma HM concentrations was UM>EM>PM. For each of the CYP2D6 phenotypes, the mean predicted HM levels were within HM's therapeutic range, which indicates HC has significant phenotype-dependent pro-drug effects.

CONCLUSIONS

Our results demonstrate that pharmacogenetics afford clinicians an opportunity to individualize HC dosing, while adding enhanced opportunity to account for its conversion to HM in the body.

Pharmacokinetics of Tramadol and O-Desmethyltramadol Enantiomers Following Administration of Extended-Release Tablets to Elderly and Young Subjects

BACKGROUND

Tramadol is frequently used in geriatric patients; however, pharmacokinetic (PK) publications on tramadol and O-desmethyltramadol (ODM) in elderly patients are rare.

OBJECTIVE

Our objective was to characterize the PK of tramadol and ODM, including absorption processes and covariates for tramadol, in elderly and young subjects after single-dose administration of 200-mg extended-release tablets.

METHODS

We conducted a PK study in 15 elderly (aged ≥75 years) subjects with mild renal insufficiency and 20 young (18-40 years) subjects; blood and urine samples were collected for 48 h post-dose. Non-compartmental analysis (NCA) of each tramadol and ODM enantiomer included area under the concentration-time curve (AUC), terminal elimination rate (k el), total body clearance, volume of distribution (V area/ F), and renal clearance (Clr0-48). A one-compartment population model of total tramadol concentration was parameterized with clearance (CL/F), volume of distribution (V/F), and mixed order absorption (first-order and zero-order absorption rate constants with lag times).

RESULTS

NCA demonstrated comparable maximum plasma concentration (C max) and AUC between age groups for tramadol enantiomers, but significant differences in V area/ F (mean 34% higher) and k el (mean 28% lower) in the elderly. PK of ODM were significantly different in the elderly for AUC0-inf (mean 35% higher), Clr0-48 (mean 29% lower), and k el (mean 33% lower). The population analysis identified age as a covariate of V/F (young 305 L; elderly 426 L), with a 50% longer mean elimination half-life in the elderly. No differences in absorption processes were observed.

CONCLUSIONS

Tramadol exposure was similar between the age groups; exposure to ODM was higher in elderly subjects.

Role of CYP2D6 Polymorphisms in the Outcome of Postoperative Pain Treatment

OBJECTIVE

To investigate the role of CYP2D6 phenotype in the outcome of postoperative (PO) pain (POP) treatment.

DESIGN

Longitudinal cohort study. Open-label trial with post hoc analysis.

SETTING

General Hospital Surgery and Recovery Units.

PATIENTS

Ninety unrelated Caucasians submitted to abdominal/thoracic surgery.

INTERVENTIONS

Standard multimodal POP treatment including opioids (tramadol) and nonsteroidal anti-inflammatory drugs (ketoprofen) at different dosages and infusion rates according to the predicted mild, moderate, or severe POP.

OUTCOME MEASURES

Pain (Numeric Rating Scale-NRS) and sedation (Ramsay Sedation Scale-RSS) up to 24 hours after surgery. By genotyping 16 CYP2D6 alleles, the four CYP2D6 phenotypes poor metabolizer (PM), intermediate metabolizers (IM), extensive metabolizers (EM) and ultrarapid metabolizers (UM) were predicted.

RESULTS

As compared with the CYP2D6-EM phenotype, in the early PO time (30 min) a higher RSS mean score in IM was observed (P = 0.035). A suggestion towards higher mean score in PM (P = 0.091) and a minor mean score in UM (P = 0.091) was also detected. No difference in the outcome of pain across the CYP2D6 phenotypes was observed.

CONCLUSIONS

In respect to the normal CYP2D6 phenotype, our results suggested that slowly metabolizers (IMs and PMs) might have a major sedation, whereas more rapid metabolizers (UM) a minor sedation, in the early time after surgery. A minor role of CYP2D6 phenotype in PO analgesia may be suggested.

Improved drug therapy: triangulating phenomics with genomics and metabolomics

Embracing the complexity of biological systems has a greater likelihood to improve prediction of clinical drug response. Here we discuss limitations of a singular focus on genomics, epigenomics, proteomics, transcriptomics, metabolomics, or phenomics-highlighting the strengths and weaknesses of each individual technique. In contrast, 'systems biology' is proposed to allow clinicians and scientists to extract benefits from each technique, while limiting associated weaknesses by supplementing with other techniques when appropriate. Perfect predictive modeling is not possible, whereas modeling of intertwined phenomic responses using genomic stratification with metabolomic modifications may greatly improve predictive values for drug therapy. We thus propose a novel-integrated approach to personalized medicine that begins with phenomic data, is stratified by genomics, and ultimately refined by metabolomic pathway data. Whereas perfect prediction of efficacy and safety of drug therapy is not possible, improvements can be achieved by embracing the complexity of the biological system. Starting with phenomics, the combination of linking metabolomics to identify common biologic pathways and then stratifying by genomic architecture, might increase predictive values. This systems biology approach has the potential, in specific subsets of patients, to avoid drug therapy that will be either ineffective or unsafe.

State of art of managing pain in patients with cancer

Pain in cancer patients involves complex interactions between physiological, psychological, sociocultural, sensory, cognitive, and behavioral dimensions. Pain management interventions will be most effective when pharmacological and nonpharmacological treatments are individualized after exploring the various contributors to pain and suffering, and the patient and family are educated and involved in decision making. This entails a systematic multidimensional approach with frequent reassessments of pain and related outcomes.

Exploring rates of abnormal pharmacogenetic findings in a pain practice

Pharmacogenetic testing (PGT) is part of increasing efforts to personalize medicine, hopefully leading to better medication selection with more effective, less toxic therapies. Pharmacogenetic testing has relevance for chronic pain treatment, given the frequent comorbidities and polypharmacy. This retrospective study explored the prevalence of polymorphisms in a specialty pain practice in Louisiana. Pharmacogenetic testing was conducted for the cytochrome P450 (CYP) enzymes CYP2B6, CYP2C19, and CYP2D6, or the uridine diphosphate-glucuronosyltransferase 2 family polypeptide B15 (UGT2B15) enzyme utilizing a noninvasive, saliva-based test based on clinical decision-making. The sample consisted of 61 men (58.7%) and 41 women (39.4%), with an average age of 46.7 years (range = 23-83, SD = 11.5 years). Across all tests, 164 (42.3%) were extensive, 99 (25.5%) were intermediate, 28 (7.2%) were ultrarapid, and 27 (7%) were poor metabolizers. Only three patients who had been tested were found to be extensive (normal) for all four genes. These data demonstrate that genetic polymorphisms were frequently encountered. Consideration should be given to obtaining PGT as an aspect of evaluation and treatment planning when working with patients in need of specialty pain consultation and care. Caution is needed, as this brief report encompasses results from a single pain practice in one geographic location with a potentially distinct prevalence of genetic polymorphisms. Further prospective study is needed.

The CYP2D6 gene determines oxycodone's phenotype-specific addictive potential: implications for addiction prevention and treatment

We propose a hypothesis for predicting addictive potential of oral drugs, in general, and oxycodone's addictive potential, in particular. We hypothesize that a patient's CYP2D6 phenotype determines oxycodone's addictive potential, in part, via genotype-specific regulation of its clearance; although, other possible modulators of oxycodone's addiction potential exist. For example, brain CYPs related to phenotype could be involved. To pilot test our hypothesis, we used a mathematical model which postulates that oxycodone's addictive potential is given by: LAP=E/(ka/ke), where LAP represents addictive potential, E represents euphoric potency, ka is the absorption rate constant of drug from the gastrointestinal tract, and ke is the systemic elimination rate constant of drug by all processes responsible for its removal from plasma. Using CYP2D6 phenotype-specific oxycodone pharmacokinetic parameter values derived from published data, our hypothesis predicted that the canonical order of oxycodone's addictive potential was UM>EM>IM>PM, with corresponding LAP values of 0.24, 0.21, 0.17, and 0.15 respectively. Our hypothesis about oxycodone's addictive potential may provide a unifying approach useful for both personalized medicine dosing and predicting addictive potential of oral drugs in humans, since it is based on both oxycodone's pharmacogenetics and pharmacokinetics.

Do CYP2D6 genotypes reflect oxycodone requirements for cancer patients treated for cancer pain? A cross-sectional multicentre study

Objective

Opioids are recommended by the World Health Organization for moderate to severe cancer pain. Oxycodone is one of the most commonly used opioids and is metabolized in the liver by CYP3A4 and CYP2D6 enzymes. The aim of this cross-sectional study was to assess the relationship between oxycodone pharmacokinetics, pharmacodynamics and the CYP2D6 genotypes “poor metaboliser” (PM), “extensive metaboliser” (EM) and “ultra-rapid metaboliser” (URM) in a cohort of patients with cancer pain.

Methods

The patients were genotyped for the most common CYP2D6 variants and serum concentrations of oxycodone and metabolites were determined. Pain was assessed using the Brief Pain Inventory (BPI). The EORTC QLQ-C30 was used to assess the symptoms of tiredness and nausea. Cognitive function was assessed by the Mini Mental State (MMS) examination. Associations were examined by analyses of variance (ANOVA) and covariance (ANCOVA), or ordinal logistic regressions with and without covariates.

Results

The sample consisted of 27 PM, 413 EM (including heterozygotes) and 10 URM. PM had lower oxymorphone and noroxymorphone serum concentrations and oxymorphone to oxycodone ratios than EM and URM. No differences between PM, EM and URM in pain intensity, nausea, tiredness or cognitive function was found.

Conclusion

CYP2D6 genotypes caused expected differences in pharmacokinetics, but they had no pharmacodynamic consequence. CYP2D6 genotypes did not influence pain control, the adverse symptoms nausea and sedation or the risk for cognitive failure in this study of patients treated with oxycodone for cancer pain.

The World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for the biological treatment of substance use and related disorders. Part 2: Opioid dependence

OBJECTIVES

To develop evidence-based practice guidelines for the pharmacological treatment of opioid abuse and dependence.

METHODS

An international task force of the World Federation of Societies of Biological Psychiatry (WFSBP) developed these practice guidelines after a systematic review of the available evidence pertaining to the treatment of opioid dependence. On the basis of the evidence, the Task Force reached a consensus on practice recommendations, which are intended to be clinically and scientifically meaningful for physicians who treat adults with opioid dependence. The data used to develop these guidelines were extracted primarily from national treatment guidelines for opioid use disorders, as well as from meta-analyses, reviews, and publications of randomized clinical trials on the efficacy of pharmacological and other biological treatments for these disorders. Publications were identified by searching the MEDLINE database and the Cochrane Library. The literature was evaluated with respect to the strength of evidence for efficacy, which was categorized into one of six levels (A-F).

RESULTS

There is an excellent evidence base supporting the efficacy of methadone and buprenorphine or the combination of buprenorphine and naloxone for the treatment of opioid withdrawal, with clonidine and lofexidine as secondary or adjunctive medications. Opioid maintenance with methadone and buprenorphine is the best-studied and most effective treatment for opioid dependence, with heroin and naltrexone as second-line medications.

CONCLUSIONS

There is enough high quality data to formulate evidence-based guidelines for the treatment of opioid abuse and dependence. This task force report provides evidence for the efficacy of a number of medications to treat opioid abuse and dependence, particularly the opioid agonists methadone or buprenorphine. These medications have great relevance for clinical practice.

Influences on the pharmacokinetics of oxycodone: a multicentre cross-sectional study in 439 adult cancer patients

Objective

Oxycodone is widely used for the treatment of cancer pain, but little is known of its pharmacokinetics in cancer pain patients. The aim of this study was to explore the relationships between ordinary patient characteristics and serum concentrations of oxycodone and the ratios noroxycodone or oxymorphone/oxycodone in cancer patients.

Methods

Four hundred and thirty-nine patients using oral oxycodone for cancer pain were included. The patients’ characteristics (sex, age, body mass index [BMI], Karnofsky performance status, “time since starting opioids”, “oxycodone total daily dose”, “time from last oxycodone dose”, use of CYP3A4 inducer/inhibitor, “use of systemic steroids”, “number of medications taken in the last 24 h”, glomerular filtration rate (GFR) and albumin serum concentrations) influence on oxycodone serum concentrations or metabolite/oxycodone ratios were explored by multiple regression analyses.

Results

Sex, CYP3A4 inducers/inhibitors, total daily dose, and “time from last oxycodone dose” predicted oxycodone concentrations. CYP3A4 inducers, total daily dose, and “number of medications taken in the last 24 h” predicted the oxymorphone/oxycodone ratio. Total daily dose, “time from last dose to blood sample”, albumin, sex, CYP3A4 inducers/inhibitors, steroids, BMI and GFR predicted the noroxycodone/oxycodone ratio.

Conclusion

Women had lower oxycodone serum concentrations than men. CYP3A4 inducers/inhibitors should be used with caution as these are predicted to have a significant impact on oxycodone pharmacokinetics. Other characteristics explained only minor parts of the variability of the outcomes.

Pharmacogenetics and forensic toxicology

Large inter-individual variability in drug response and toxicity, as well as in drug concentrations after application of the same dosage, can be of genetic, physiological, pathophysiological, or environmental origin. Absorption, distribution and metabolism of a drug and interactions with its target often are determined by genetic differences. Pharmacokinetic and pharmacodynamic variations can appear at the level of drug metabolizing enzymes (e.g., the cytochrome P450 system), drug transporters, drug targets or other biomarker genes. Pharmacogenetics or toxicogenetics can therefore be relevant in forensic toxicology. This review presents relevant aspects together with some examples from daily routines.

Recent Publications on Medications and Pharmacy

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