Pharmacogenomics of oxycodone: a narrative literature review

Implementing a pragmatic clinical trial to tailor opioids for chronic pain on behalf of the IGNITE ADOPT PGx investigators

Chronic pain is a prevalent condition with enormous economic burden. Opioids such as tramadol, codeine, and hydrocodone are commonly used to treat chronic pain; these drugs are activated to more potent opioid receptor agonists by the hepatic CYP2D6 enzyme. Results from clinical studies and mechanistic understandings suggest that CYP2D6-guided therapy will improve pain control and reduce adverse drug events. However, CYP2D6 is rarely used in clinical practice due in part to the demand for additional clinical trial evidence. Thus, we designed the ADOPT-PGx (A Depression and Opioid Pragmatic Trial in Pharmacogenetics) chronic pain study, a multicenter, pragmatic, randomized controlled clinical trial, to assess the effect of CYP2D6 testing on pain management. The study enrolled 1048 participants who are taking or being considered for treatment with CYP2D6-impacted opioids for their chronic pain. Participants were randomized to receive immediate or delayed (by 6 months) genotyping of CYP2D6 with clinical decision support (CDS). CDS encouraged the providers to follow the CYP2D6-guided trial recommendations. The primary study outcome is the 3-month absolute change in the composite pain intensity score assessed using Patient-Reported Outcomes Measurement Information System (PROMIS) measures. Follow-up will be completed in July 2024. Herein, we describe the design of this trial along with challenges encountered during enrollment.

Oxycodone enhances antitumor effect of paclitaxel on human breast cancer SKBR3 cells in vitro

BACKGROUND

The influences of Oxycodone (OXY) combined with Paclitaxel (PTX) on breast cancer cells are unclear. The present study aimed to examine the effects of OXY combined with PTX on the proliferation, apoptosis, and migration of human breast cancer SKBR3 cells and the underlying mechanism.

METHODS

The proliferation, apoptosis and invasion of SKBR3 cells were assessed by CCK-8, colony formation assay, flowcytometric, Transwell assay and scratch assays, respectively. In addition, Western blotting was used to detect the expression of related proteins in these cells. The autophagic bodies were observed under a transmission electron microscope.

RESULTS

OXY (0.25, 0.5 and 1 mM) significantly inhibited the viability, colony-forming, migration, and invasion of SKBR3 cells as compared to the control group. Furthermore, OXY (0.25, 0.5 and 1 mM) markedly induced the apoptosis of SKBR3 cells and the levels of apoptosis-related proteins. In addition, OXY (0.25, 0.5 and 1 mM) and PTX inhibited the proliferation of SKBR3 cells synergistically as compared to PTX group in vitro. Moreover, OXY (0.25, 0.5 and 1 mM) significantly elevated the PTX-induced apoptosis in SKBR3 cells via downregulating the expression of N-cadherin, Becline-1 LC3-Ⅱ, p-Akt and p-mTOR and upregulating E-cadherin expression. Compared with the control group, OXY (1 mM) treatment induced autophagy in SKBR3 cells.

CONCLUSIONS

The present study indicates that OXY can enhance the antitumor effect of PTX on breast cancer in vitro. Hence, the combination of OXY with PTX may serve as a potential strategy for the treatment of breast cancer.

Exploring the impact of CYP2D6 and UGT2B7 gene-drug interactions, and CYP-mediated DDI on oxycodone and oxymorphone pharmacokinetics using physiologically-based pharmacokinetic modeling and simulation

Oxycodone is one of the most commonly used opioids to treat moderate to severe pain. It is metabolized mainly by CYP3A4 and CYP2D6, while only a small fraction of the dose is excreted unchanged into the urine. Oxymorphone, the metabolite primarily formed by CYP2D6, has a 40- to 60-fold higher mu-opioid receptor affinity than the parent compound. While CYP2D6-mediated gene-drug-interactions (GDIs) and drug-drug interactions (DDIs) are well-studied, they only account for a portion of the variability in oxycodone and oxymorphone exposure. The combined impact of CYP2D6-mediated GDIs and DDIs, CYP3A4-mediated DDIs, and UGT2B7 GDIs is not fully understood yet and hard to study in head-to-head clinical trials given the relatively large number of scenarios. Instead, we propose the use of a physiologically-based pharmacokinetic model that integrates available information on oxycodone's metabolism to characterize and predict the impact of DDIs and GDIs on the exposure of oxycodone and its major, pharmacologically-active metabolite oxymorphone. To this end, we first developed and verified a PBPK model for oxycodone and its metabolites using published clinical data. The verified model was then applied to determine the dose-exposure relationship of oxycodone and oxymorphone stratified by CYP2D6 and UGT2B7 phenotypes respectively, and administered perpetrators of CYP-based drug interactions. Our simulations demonstrate that the combination of CYP2D6 UM and a UGT2B7Y (268) mutation may lead to a 2.3-fold increase in oxymorphone exposure compared to individuals who are phenotyped as CYP2D6 NM / UGT2B7 NM. The extent of oxymorphone exposure increases up to 3.2-fold in individuals concurrently taking CYP3A4 inhibitors, such as ketoconazole. Inhibition of the CYP3A4 pathway results in a relative increase in the partial metabolic clearance of oxycodone to oxymorphone. Oxymorphone is impacted to a higher extent by GDIs and DDIs than oxycodone. We predict oxymorphone exposure to be highest in CYP2D6 UMs/UGT2B7 PMs in the presence of ketoconazole (strong CYP3A4 index inhibitor) and lowest in CYP2D6 PMs/UGT2B7 NMs in the presence of rifampicin (strong CYP3A4 index inducer) covering a 55-fold exposure range.

The Impact of Opioid Receptor Gene Polymorphism on Fentanyl and Alfentanil's Analgesic Effects in the Pediatric Perioperative Period

Introduction

The polymorphism of the gene coding mu-opioid receptor (OPRM1) is one of the factors contributing to the variability in the response to opioid analgesics in children. The goal of this study is to investigate its role in association with postoperative acute pain in children of various ages.

Methods

This prospective study analyzed 110 pediatric patients, after plastic or orthopedic surgery, who were genotyped and randomly assigned to receive fentanyl or alfentanil. Postoperative pain was rated using Numerical Rating Scale (0-10). All the patients were genotyped forOPRM1 118A>G (rs1799971) gene polymorphism.

Results

School children under the age of 11 with the OPRM1 AA genotype were shown to have a higher BMI (p<0.05). Children over the age of 12 carrying G allele OPRM1, had increased postoperative pain sensitivity and intensity (3.28±1.95 vs 4.91±2.17; p<0.05), as compared to AA allele carriers.

Discussion

OPRM1 118A>G polymorphism may explain the variation in the perception of postoperative pain in children over the age of 12 and may be a useful predictor for adjusting the dose of analgesics, but the dose is relative to the patient's needs regardless of his genetic characteristics. In younger children, carriers of polymorphic OPRM1 118G allele may be protected from obesity, due to diminished MOP expression.

Efficacy and Safety of Analgesics and Sedatives during Radiofrequency Catheter Ablation of Atrial Fibrillation: A Network Meta-Analysis

Background

Atrial fibrillation is the most common tachyarrhythmia, while catheter ablation is an effective therapy for atrial fibrillation. However, pain and nervousness may occur during the procedure. Moreover, a consensus has still not been reached on which is the best kind of analgesic and sedative to use in these procedures. Therefore, we conducted a network meta-analysis to evaluate the efficacy and safety of analgesics and sedatives used in catheter ablation for atrial fibrillation.

Methods

We searched PubMed, Cochrane Library, Web of Science, EMBASE, China National Knowledge Infrastructure, and Baidu Wenku document download website for randomized controlled trials from their inception to February 26, 2023. Only studies that made comparisons among analgesics or sedatives and involved patients with atrial fibrillation undergoing radiofrequency catheter ablation were included. The efficacy endpoints were Ramsay sedation scores and visual analog scale scores during the radiofrequency catheter ablation for atrial fibrillation. The safety endpoints were the incidence of respiratory depression, hypotension, nausea, and vomiting. Pairwise comparisons and frequency method analyses were conducted. Results were reported as odds ratio (OR), mean difference (MD), and corresponding 95% confidence intervals (CIs). We assessed the risk bias of the studies in accordance with the Cochrane Handbook for Systematic Reviews of Interventions.

Results

Out of the 709 articles initially retrieved, 14 studies, with a total of 1156 participants, were included. In terms of efficacy, patients receiving dexmedetomidine during radiofrequency ablation for atrial fibrillation had higher Ramsay sedation scores than those receiving midazolam plus fentanyl, or its derivatives (MD -0.88, 95% CI [-0.04 to -0.72]). Compared with morphine, dezocine (MD 1.88, 95% CI [1.16 to 2.60]), hydromorphone (MD 4.07, 95% CI [3.56 to 4.58]), butorphanol (MD 3.18, 95% CI [2.38 to 3.96]), and fentanyl or its derivatives (MD 1.57, 95% CI [1.25 to 1.89]) had a better analgesic effect. In terms of safety, propofol (OR 16.46; 95% CI [1.54 to 175.95]) and midazolam plus fentanyl or its derivatives (OR 7.02; 95% CI [1.33 to 36.99]) significantly increased the incidence of respiratory depression compared with dexmedetomidine plus fentanyl or its derivatives. Dexmedetomidine plus fentanyl or its derivatives reduced the incidence of nausea and vomiting compared with fentanyl alone (OR 4.74; 95% CI [1.01 to 22.22]). Propofol was associated with a lower incidence of nausea and vomiting than hydromorphone (OR 0.01; 95% CI [0.00 to 0.59]) and fentanyl or its derivatives (OR 0.01; 95% CI [0.00 to 0.51]). There was no statistically significant difference in the incidence of hypotension between any two strategies.

Conclusions

Hydromorphone and butorphanol had better analgesic effects than fentanyl or its derivates. Dexmedetomidine had better sedative effects. In terms of safety, dexmedetomidine, oxymorphone, and butorphanol were superior. It is necessary to explore the regimen that can consider both the effectiveness and safety during radiofrequency catheter ablation for atrial fibrillation (AF).

The PROSPERO Registration

This study was registered with PROSPERO, number: CRD42023403661.

Oxycodone-acetaminophen versus celecoxib for postoperative pain in knee osteoarthritis patients after total knee arthroplasty: a randomized, controlled study

PURPOSE

Oxycodone-acetaminophen is a synergic combination of semisynthetic opioid agonis and analgesic/antipyretic agent, which improves analgesic efficacy. This randomized, controlled study intended to evaluate the analgesic efficacy and tolerance of oxycodone-acetaminophen compared to celecoxib alone in post-total knee arthroplasty (TKA) knee osteoarthritis patients.

METHODS

One hundred and six knee osteoarthritis patients were randomized into oxycodone-acetaminophen group (N = 54) and celecoxib group (N = 52) at a 1:1 ratio. Each patient orally received oxycodone-acetaminophen (5 mg/325 mg, four times per day) or celecoxib (200 mg, twice per day) from 2 h to day (D) 3 after TKA; meanwhile, each patient received 2-day patient-controlled analgesia (PCA). The primary outcome was pain visual analog scale (VAS) score at rest; other assessments were the secondary outcomes.

RESULTS

Pain VAS scores at rest at D1, D2, D3, and pain VAS scores at flexion at D0.5, D1, D2, D3 were lower in oxycodone-acetaminophen group compared to celecoxib group (all P < 0.050). Besides, extra (P < 0.001) and total (P < 0.001) PCA consumption were declined in oxycodone-acetaminophen group compared with celecoxib group. Furthermore, patients' satisfaction score at D3 (P = 0.012) and D7 (P = 0.043) was higher in oxycodone-acetaminophen group versus celecoxib group. Hospital for special surgery knee score (HSS) at preoperation, M1, and M3 did not differ between the two groups (all P > 0.050). The incidences of all adverse events were not varied between oxycodone-acetaminophen and celecoxib groups (all P > 0.050).

CONCLUSION

Oxycodone-acetaminophen exerts superior analgesic efficacy, patients' satisfaction, and similar tolerance compared to celecoxib in post-TKA knee osteoarthritis patients.

Oxycodone: A Current Perspective on Its Pharmacology, Abuse, and Pharmacotherapeutic Developments

Oxycodone, a semisynthetic derivative of naturally occurring thebaine, an opioid alkaloid, has been available for more than 100 years. Although thebaine cannot be used therapeutically due to the occurrence of convulsions at higher doses, it has been converted to a number of other widely used compounds that include naloxone, naltrexone, buprenorphine, and oxycodone. Despite the early identification of oxycodone, it was not until the 1990s that clinical studies began to explore its analgesic efficacy. These studies were followed by the pursuit of several preclinical studies to examine the analgesic effects and abuse liability of oxycodone in laboratory animals and the subjective effects in human volunteers. For a number of years oxycodone was at the forefront of the opioid crisis, playing a significant role in contributing to opioid misuse and abuse, with suggestions that it led to transitioning to other opioids. Several concerns were expressed as early as the 1940s that oxycodone had significant abuse potential similar to heroin and morphine. Both animal and human abuse liability studies have confirmed, and in some cases amplified, these early warnings. Despite sharing a similar structure with morphine and pharmacological actions also mediated by the μ-opioid receptor, there are several differences in the pharmacology and neurobiology of oxycodone. The data that have emerged from the many efforts to analyze the pharmacological and molecular mechanism of oxycodone have generated considerable insight into its many actions, reviewed here, which, in turn, have provided new information on opioid receptor pharmacology. SIGNIFICANCE STATEMENT: Oxycodone, a μ-opioid receptor agonist, was synthesized in 1916 and introduced into clinical use in Germany in 1917. It has been studied extensively as a therapeutic analgesic for acute and chronic neuropathic pain as an alternative to morphine. Oxycodone emerged as a drug with widespread abuse. This article brings together an integrated, detailed review of the pharmacology of oxycodone, preclinical and clinical studies of pain and abuse, and recent advances to identify potential opioid analgesics without abuse liability.

Pharmacological Treatments and Therapeutic Drug Monitoring in Patients with Chronic Pain

Pain is an unpleasant sensory and emotional experience that affects every aspect of a patient's life and which may be treated through different pharmacological and non-pharmacological approaches. Analgesics are the drugs most commonly used to treat pain, and in specific situations, the use of opioids may be considered with caution. These drugs, in fact, do not always induce optimal analgesia in patients, and several problems are associated with their use. The purpose of this narrative review is to describe the pharmacological approaches currently used for the management of chronic pain. We review several aspects, from the pain-scale-based methods currently available to assess the type and intensity of pain, to the most frequently administered drugs (non-narcotic analgesics and narcotic analgesics), whose pharmacological characteristics are briefly reported. Overall, we attempt to provide an overview of different pharmacological treatments while also illustrating the relevant guidelines and indications. We then report the strategies that may be used to reduce problems related to opioid use. Specifically, we focus our attention on therapeutic drug monitoring (TDM), a tool that could help clinicians select the most suitable drug and dose to be used for each patient. The actual potential of using TDM to optimize and personalize opioid-based pain treatments is finally discussed based on recent scientific reports.

Pharmacogenetic Analysis Enables Optimization of Pain Therapy: A Case Report of Ineffective Oxycodone Therapy

Patients suffering from chronic pain may respond differently to analgesic medications. For some, pain relief is insufficient, while others experience side effects. Although pharmacogenetic testing is rarely performed in the context of analgesics, response to opiates, non-opioid analgesics, and antidepressants for the treatment of neuropathic pain can be affected by genetic variants. We describe a female patient who suffered from a complex chronic pain syndrome due to a disc hernia. Due to insufficient response to oxycodone, fentanyl, and morphine in addition to non-steroidal anti-inflammatory drug (NSAID)-induced side effects reported in the past, we performed panel-based pharmacogenotyping and compiled a medication recommendation. The ineffectiveness of opiates could be explained by a combined effect of the decreased activity in cytochrome P450 2D6 (CYP2D6), an increased activity in CYP3A, and an impaired drug response at the µ-opioid receptor. Decreased activity for CYP2C9 led to a slowed metabolism of ibuprofen and thus increased the risk for gastrointestinal side effects. Based on these findings we recommended hydromorphone and paracetamol, of which the metabolism was not affected by genetic variants. Our case report illustrates that an in-depth medication review including pharmacogenetic analysis can be helpful for patients with complex pain syndrome. Our approach highlights how genetic information could be applied to analyze a patient's history of medication ineffectiveness or poor tolerability and help to find better treatment options.

Patterns and Trends in Pharmacological Treatment for Outpatients with Postherpetic Neuralgia in Six Major Areas of China, 2015-2019

The aim of this study was to assess the patterns and trends of pharmacological treatment for outpatients with postherpetic neuralgia (PHN) in China in the period 2015-2019. Prescription data for outpatients with PHN were extracted from the database of the Hospital Prescription Analysis Program of China according to the inclusion criteria. The trends in yearly prescriptions and corresponding costs were analyzed and stratified by drug class and specific drugs. A total of 19,196 prescriptions from 49 hospitals in 6 major regions of China were included for analysis. The yearly prescriptions increased from 2534 in 2015 to 5676 in 2019 (p = 0.027), and the corresponding expenditures increased from CNY 898,618 in 2015 to CNY 2,466,238 in 2019 (p = 0.027). Gabapentin and pregabalin are the most commonly used drugs for PHN, and more than 30% of these two drugs were combined with mecobalamin. Opioids were the second most frequently prescribed drug class, and oxycodone accounted for the largest share of the cost. Topical drugs and TCAs are rarely used. The frequent use of pregabalin and gabapentin was in accordance with current guidelines; however, the use of oxycodone raised concerns about rationality and economic burden. The results of this study may benefit the allocation of medical resources and management for PHN in China and other countries.

Effects of oxycodone pharmacogenetics on postoperative analgesia and related clinical outcomes in children: a pilot prospective study

Background: Variability in the pharmacokinetics and pharmacodynamics of oxycodone in children undergoing surgery could be due to genetic polymorphisms. Materials & methods: The authors studied the association between clinical outcomes and pharmacogenes in children undergoing major surgery. A total of 89 children (35 undergoing pectus excavatum repair and 54 undergoing spinal fusion) were recruited. Results: OPRM1 SNP rs6902403 showed an association with maximum pain score and total morphine equivalent dose (p < 0.05). Other polymorphisms in OPRM1 SNP, PXR, COMT and ABCB1 were also shown to be associated with average morphine equivalent dose, length of hospital stay and maximum surgical pain (p < 0.05). Conclusion: This study demonstrates novel associations between the above pharmacogenes and oxycodone's pharmacokinetics as well as postoperative outcomes in children. Clinical trial registration: NCT03495388 (ClinicalTrials.gov).

Association of CYP2D6 genotype predicted phenotypes with oxycodone requirements and side effects in children undergoing surgery

Background

Oxycodone is a commonly used oral opioid in children for treating postoperative pain. Highly polymorphic gene CYP2D6 metabolizes oxycodone into its more potent metabolite, oxymorphone. We hypothesized that altered activity due to CYP2D6 polymorphisms will influence oxycodone requirements {relative oxycodone use [oxycodone morphine equivalents (MEq)/total MEq] to maintain analgesia} (primary outcome) and risk for oxycodone induced side-effects such as respiratory depression (RD) and emesis (secondary outcomes). We also explored the influence of genotype availability and provider guidance on oral opioid prescription patterns.

Methods

Patients who underwent Nuss procedure and spine fusion with CYP2D6 genotyping results available preoperatively were included. Data on demographics, genotypes, oral opioids, pain scores, RD and emesis were collected. Univariate and multivariable regression for comparison of CYP2D6 genotype predicted poor, ultrarapid, intermediate metabolizers (PM, UM and IM) phenotype with normal metabolizers (NM) for outcomes were performed. Stratified logistic regression was conducted in low (oxycodone/total MEq <0.5) and high (and oxycodone/total MEq >0.5) oxycodone use groups for RD and emesis, with application of firth correction due to quasi-complete separations. Breslow-Day test was used to evaluate odds ratios for prescribing genotype directed opioid between control group (2012-15) (where providers were alerted to genotyping results availability but not directed to use them while prescribing) and genotype directed groups (2016-18) (where providers were directed to use the genotyping results available to them while prescribing oxycodone after surgery).

Results

Of 193 subjects (age 15.9±0.25 years, 28.5% female, 93.78% White; 101 NM, 76 IM, 10 PM and 6 UM), 77.72% underwent pectus surgery. CYP2D6 phenotype was associated with oxycodone MEq/total MEq requirements (P<0.001). Both PM and UM phenotypes had lower oxycodone requirements compared to NM [-0.316 (SE 0.098), P=0.005 and -0.432 (SE 0.113), P<0.001 respectively]. CYP2D6 phenotype was associated with RD in high use oxycodone group (P=0.018) but not low use oxycodone groups (P=0.634). No phenotype association was found for emesis. Oxycodone was prescribed to 91.24% of NM/IM vs. 66.67% of PM/UM (P=0.129) in control group and 94.64% of NM/IM vs. 28.57% of PM/UM (P<0.001) in the genotype-directed group. PM/UM phenotypes in genotype directed group had a lower chance of being prescribed oxycodone (effect size =-2.775; SE 1.566; P=0.076).

Conclusions

Our findings suggest CYP2D6 genotypes are associated with oxycodone requirements for analgesia and may influence risk for RD. Genotype availability and guidance likely influence oral opioid prescription pattern after surgery. Our findings are limited by small sample size for UM/PM groups.

The respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine

Background and Purpose

Mitragynine, the major alkaloid in Mitragyna speciosa (kratom), is a partial agonist at the μ opioid receptor. CYP3A‐dependent oxidation of mitragynine yields the metabolite 7‐OH mitragynine, a more efficacious μ receptor agonist. While both mitragynine and 7‐OH mitragynine can induce anti‐nociception in mice, recent evidence suggests that 7‐OH mitragynine formed as a metabolite is sufficient to explain the anti‐nociceptive effects of mitragynine. However, the ability of 7‐OH mitragynine to induce μ receptor‐dependent respiratory depression has not yet been studied.

Experimental Approach

Respiration was measured in awake, freely moving, male CD‐1 mice, using whole body plethysmography. Anti‐nociception was measured using the hot plate assay. Morphine, mitragynine, 7‐OH mitragynine and the CYP3A inhibitor ketoconazole were administered orally.

Key Results

The respiratory depressant effects of mitragynine showed a ceiling effect, whereby doses higher than 10 mg·kg⁻¹ produced the same level of effect. In contrast, 7‐OH mitragynine induced a dose‐dependent effect on mouse respiration. At equi‐depressant doses, both mitragynine and 7‐OH mitragynine induced prolonged anti‐nociception. Inhibition of CYP3A reduced mitragynine‐induced respiratory depression and anti‐nociception without affecting the effects of 7‐OH mitragynine.

Conclusions and Implications

Both the anti‐nociceptive effects and the respiratory depressant effects of mitragynine are partly due to its metabolic conversion to 7‐OH mitragynine. The limiting rate of conversion of mitragynine into its active metabolite results in a built‐in ceiling effect of the mitragynine‐induced respiratory depression. These data suggest that such ‘metabolic saturation’ at high doses may underlie the improved safety profile of mitragynine as an opioid analgesic.

Pharmacogenetics of Addiction Therapy

Drug addiction is a serious relapsing disease that has high costs to society and to the individual addicts. Treatment of these addictions is still in its nascency, with only a few examples of successful therapies. Therapeutic response depends upon genetic, biological, social, and environmental components. A role for genetic makeup in the response to treatment has been shown for several addiction pharmacotherapies with response to treatment based on individual genetic makeup. In this chapter, we will discuss the role of genetics in pharmacotherapies, specifically for cocaine, alcohol, and opioid dependences. The continued elucidation of the role of genetics should aid in the development of new treatments and increase the efficacy of existing treatments.

The Role of Pharmacogenomics in Postoperative Pain Management

Pharmacogenomics can improve pain management by considering individual variations in pain perception and susceptibility and sensitivity to medicines related to genetic diversity. Due to the subjective nature of pain and the fact that people respond differently to medicines, it can be challenging to develop a consistent and successful regimen for pain disorders. Numerous factors influence the outcome of pain treatment programs, but two stand out: altered perception of pain and varying responsiveness to analgesic medicines. Numerous polymorphisms in genes such as CYP2D6, OPRM1, and ABCB1 have been identified, culminating in a heterogeneous response to pain medication in people who have these genetic polymorphisms. Improved treatment regimens that factor in pharmacogenetic differences in patients would help reduce the risk of opioid dependency and help effectively treat postoperative pain.