CYP2D6 phenotypes and opioid metabolism: the path to personalized analgesia

Artificial intelligence to predict inhibitors of drug-metabolizing enzymes and transporters for safer drug design

INTRODUCTION

Drug-metabolizing enzymes (DMEs) and transporters (DTs) play integral roles in drug metabolism and drug-drug interactions (DDIs) which directly impact drug efficacy and safety. It is well-established that inhibition of DMEs and DTs often leads to adverse drug reactions (ADRs) and therapeutic failure. As such, early prediction of such inhibitors is vital in drug development. In this context, the limitations of the traditional in vitro assays and QSAR models methods have been addressed by harnessing artificial intelligence (AI) techniques.

AREAS COVERED

This narrative review presents the insights gained from the application of AI for predicting DME and DT inhibitors over the past decade. Several case studies demonstrate successful AI applications in enzyme-transporter interaction prediction, and the authors discuss workflows for integrating these predictions into drug design and regulatory frameworks.

EXPERT OPINION

The application of AI in predicting DME and DT inhibitors has demonstrated significant potential toward enhancing drug safety and effectiveness. However, critical challenges involve the data quality, biases, and model transparency. The availability of diverse, high-quality datasets alongside the integration of pharmacokinetic and genomic data are essential. Lastly, the collaboration among computational scientists, pharmacologists, and regulatory bodies is pyramidal in tailoring AI tools for personalized medicine and safer drug development.

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

INTRODUCTION

Drug-drug interactions (DDIs) are among factors that may affect the efficacy and safety of opioid treatment. Data on clinically manifested DDIs are scarse, and recommendations that might guide physicians are presently lacking. The aim of this study was to update a systematic review (2015) on studies reporting clinically significant DDIs involving opioids used for pain treatment in adult patients with cancer.

METHODS

Systematic literature searches in MEDLINE, Embase, and Cochrane Central Register of Controlled Trials from the start of the databases through 18 September 2023.

RESULTS

Of the 1968 retrieved papers, 16 were included in the final analysis, together with five papers identified through hand-searching of reference lists. Nineteen publications were case reports or case series. Nine, sixteen, and eight patients presented adverse effects from opioids, impaired pain control, or opioid withdrawal, respectively. The main mechanisms underlying DDIs were alteration of cytochrome P450 3A4 activity and pharmacodynamic antagonism resulting from concurrent use of an opioid analgesic and a peripheral mu-opioid receptor antagonist (PAMORA).

CONCLUSION

Knowledge about clinically significant DDIs associated with opioids in cancer patients is currently mostly based upon case reports. These cases give information about drug combinations that should be recognized as potentially harmful by physicians prescribing opioids.

PROSPERO ID

CRD42023481103.

Brain Cytochrome P450: Navigating Neurological Health and Metabolic Regulation

Human cytochrome P450 (CYP) enzymes in the brain represent a crucial frontier in neuroscience, with far-reaching implications for drug detoxification, cellular metabolism, and the progression of neurodegenerative diseases. The brain's complex architecture, composed of interconnected cell types and receptors, drives unique neuronal signaling pathways, modulates enzyme functions, and leads to distinct CYP gene expression and regulation patterns compared to the liver. Despite their relatively low levels of expression, brain CYPs exert significant influence on drug responses, neurotoxin susceptibility, behavior, and neurological disease risk. These enzymes are essential for maintaining brain homeostasis, mediating cholesterol turnover, and synthesizing and metabolizing neurochemicals, neurosteroids, and neurotransmitters. Moreover, they are key participants in oxidative stress responses, neuroprotection, and the regulation of inflammation. In addition to their roles in metabolizing psychotropic drugs, substances of abuse, and endogenous compounds, brain CYPs impact drug efficacy, safety, and resistance, underscoring their importance beyond traditional drug metabolism. Their involvement in critical physiological processes also links them to neuroprotection, with significant implications for the onset and progression of neurodegenerative diseases. Understanding the roles of cerebral CYP enzymes is vital for advancing neuroprotective strategies, personalizing treatments for brain disorders, and developing CNS-targeting therapeutics. This review explores the emerging roles of CYP enzymes, particularly those within the CYP1-3 and CYP46 families, highlighting their functional diversity and the pathological consequences of their dysregulation on neurological health. It also examines the potential of cerebral CYP-based biomarkers to improve the diagnosis and treatment of neurodegenerative disorders, offering new avenues for therapeutic innovation.

Sex differences in CYP450-based sodium dehydroacetate metabolism and its metabolites in rats

Sodium dehydroacetate (DHA-Na), a widely used preservative, can induce sex-differentiated coagulation disorders primarily resulting from its metabolism. However, the underlying mechanisms remain poorly understood. Here, we identified several Cytochrome P450 (CYP450) sub-enzymes involved in sex differences related to DHA-Na metabolism, along with two related DHA-Na metabolites. CYP1A2, CYP3A2, and CYP2D1 were primarily responsible for DHA-Na metabolism, which was stronger in male rats than in female rats. Inhibition of these isoforms separately resulted in the DHA-Na metabolic capacity in male rats becoming equal to, or even weaker than, that in female rats. Furthermore, Cyp1a2, Cyp3a2, Cyp2d1, and Cyp2c11 expression was higher in male rats than in female rats, suggesting these enzymes are related to exhibited sex differences in DHA-Na metabolism. Moreover, 3-glycoloyl-6-methy-2,3-dihydropyran-2,4-dione (C8H8O5) and 3-imino-6-methyl-2,3-dihydropran-2,4dione (C6H5O3N) were identified as the two main DHA-Na metabolites. These findings provide crucial insights into potential mechanisms underlying sex differences in DHA-Na metabolism and its metabolites in rats.

Case report: Dezocine's rapid and sustained antidepressant effects

Anhedonia and motivational impairments are cardinal features of depression, against which conventional antidepressants demonstrate limited efficacy. Preclinical investigations and extant clinical trial data substantiate the promise of opioid receptor modulators in addressing anhedonia, depression, and anxiety. While synthetic opioid agents like dezocine are conventionally employed for analgesia, their distinctive pharmacological profile has engendered interest in their potential antidepressant properties and translational applications. Herein, we present a case in which persistent bupropion treatment was ineffective. However, the incidental administration of a single low-dose intravenous injection of dezocine resulted in a rapid and sustained amelioration of depressive symptoms, particularly anhedonia and motivational deficits. Our findings posit a potentially novel role for the "legacy drug" dezocine.

Use of CYP2D6 substrates and inhibitors during pain management with analgesic opioids: Drug-drug interactions that lead to lack of analgesic effectiveness

BACKGROUND

Several opioids have pharmacogenetic and drug-drug interactions which may compromise their analgesic effectiveness, but are not routinely implemented into supportive pain management. We hypothesized that CYP2D6 phenotypes and concomitant use of CYP2D6 substrates or inhibitors would correlate with opioid analgesic outcomes.

MATERIALS AND METHODS

An observational cross-sectional study was conducted with 263 adult chronic non cancer pain (CNCP) patients from a real-world pain unit under long-term CYP2D6-related opioid treatment (tramadol, hydromorphone, tapentadol or oxycodone). Metabolizer phenotype (ultrarapid [UM], normal [NM], intermediate [IM] or poor [PM]) was determined by the CYP2D6 genotype. The socio-demographic (sex, age, employment status), clinical (pain intensity and relief, neuropathic component, quality of life, disability, anxiety and depression), pharmacological (opioid doses and concomitant pharmacotherapy) and safety (adverse events) variables were recorded.

RESULTS

The whole population (66 % female, 65 (14) years old, 70 % retired and 63 % attended for low back pain) were classified as PM (5 %), IM (32 %), NM (56 %) and UM (6 %). Multiple linear and logistic regressions showed higher pain intensity and neuropathic component at younger ages when using any CYP2D6 substrate (p = 0.022) or inhibitor (p = 0.030) drug, respectively, with poorer pain relief when CYP2D6 inhibitors (p=0.030) were present.

CONCLUSION

The concomitant use of CYP2D6 substrates or inhibitors during opioid therapy for CNCP may result in lack of analgesic effectiveness. This aspect could be relevant for pharmacological decision making during CNCP management.

Sex-Gender Differences Are Completely Neglected in Treatments for Neuropathic Pain

As sex-gender differences have been described in the responses of patients to certain medications, we hypothesized that the responses to medications recommended for neuropathic pain may differ between men and women. We conducted a literature review to identify articles reporting potential sex-gender differences in the efficacy and safety of these medications. Only a limited number of studies investigated potential sex-gender differences. Our results show that women seem to achieve higher blood concentrations than men during treatment with amitriptyline, nortriptyline, duloxetine, venlafaxine, and pregabalin. Compared to men, higher rates of women develop side effects during treatment with gabapentin, lidocaine, and tramadol. Globally, the sex-gender differences would suggest initially administering smaller doses of these medications to women with neuropathic pain compared to those administered to men. However, most of these differences have been revealed by studies focused on the treatment of other diseases (e.g., depression). Studies focused on neuropathic pain have overlooked potential sex-gender differences in patient responses to medications. Despite the fact that up to 60% of patients with neuropathic pain fail to achieve an adequate response to medications, the potential role of sex-gender differences in the efficacy and safety of pharmacotherapy has not adequately been investigated. Targeted studies should be implemented to facilitate personalized treatments for neuropathic pain.

Clinical prediction of opioid use disorder in chronic pain patients: a cohort-retrospective study with a pharmacogenetic approach

BACKGROUND

Opioids are widely used in chronic non-cancer pain (CNCP) management. However, they remain controversial due to serious risk of causing opioid use disorder (OUD). Our main aim was to develop a predictive model for future clinical translation that include pharmacogenetic markers.

METHODS

An observational study was conducted in 806 pre-screened Spanish CNCP patients, under long-term use of opioids, to compare cases (with OUD, N.=137) with controls (without OUD, N.=669). Mu-opioid receptor 1 (OPRM1, A118G, rs1799971) and catechol-O-methyltransferase (COMT, G472A, rs4680) genetic variants plus cytochrome P450 2D6 (CYP2D6) liver enzyme phenotypes were analyzed. Socio-demographic, clinical and pharmacological outcomes were also registered. A logistic regression model was performed. The model performance and diagnostic accuracy were calculated.

RESULTS

OPRM1-AA genotype and CYP2D6 poor and ultrarapid metabolizers together with three other potential predictors: 1) age; 2) work disability; 3) oral morphine equivalent daily dose (MEDD), were selected with a satisfactory diagnostic accuracy (sensitivity: 0.82 and specificity: 0.85), goodness of fit (P=0.87) and discrimination (0.89). Cases were ten-year younger with lower incomes, more sleep disturbances, benzodiazepines use, and history of substance use disorder in front of controls.

CONCLUSIONS

Functional polymorphisms related to OPRM1 variant and CYP2D6 phenotypes may predict a higher OUD risk. Established risk factors such as young age, elevated MEDD and lower incomes were identified. A predictive model is expected to be implemented in clinical setting among CNCP patients under long-term opioids use.

Ethical issues in pain and palliation

PURPOSE OF REVIEW

Increased public awareness of ethical issues in pain and palliative care, along with patient advocacy groups, put pressure on healthcare systems and professionals to address these concerns.Our aim is to review the ethics dilemmas concerning palliative care in ICU, artificial intelligence applications in pain therapy and palliative care, and the opioids epidemics.

RECENT FINDINGS

In this focus review, we highlighted state of the art papers that were published in the last 18 months, on ethical issues in palliative care within the ICU, artificial intelligence trajectories, and how opioids epidemics has impacted pain management practices (see Visual Abstract).

SUMMARY

Palliative care in the ICU should involve a multidisciplinary team, to mitigate patients suffering and futility. Providing spiritual support in the ICU is an important aspect of holistic patient care too.Increasingly sophisticated tools for diagnosing and treating pain, as those involving artificial intelligence, might favour disparities in access, cause informed consent problems, and surely, they need prudence and reproducibility.Pain clinicians worldwide continue to face the ethical dilemma of prescribing opioids for patients with chronic noncancer pain. Balancing the need for effective pain relief with the risk of opioid misuse, addiction, and overdose is a very controversial task.

Pharmacogenetic Guided Opioid Therapy Improves Chronic Pain Outcomes and Comorbid Mental Health: A Randomized, Double-Blind, Controlled Study

Interindividual variability in analgesic response is at least partly due to well-characterized polymorphisms that are associated with opioid dosing and adverse outcomes. The Clinical Pharmacogenetics Implementation Consortium (CPIC) has put forward recommendations for the CYP2D6 phenotype, but the list of studied drug-gene pairs continues to grow. This clinical trial randomized chronic pain patients (n = 60), referred from primary care to pain unit care into two opioid prescribing arms, one guided by CYP2D6, μ-opioid receptor (OPRM1), and catechol-O-methyl transferase (COMT) genotypes vs. one with clinical routine. The genotype-guided treatment reduced pain intensity (76 vs. 59 mm, p < 0.01) by improving pain relief (28 vs. 48 mm, p < 0.05), increased quality of life (43 vs. 56 mm p < 0.001), and lowered the incidence of clinically relevant adverse events (3 [1-5] vs. 1 [0-2], p < 0.01) and 42% opioid dose (35 [22-61] vs. 60 [40-80] mg/day, p < 0.05) as opposed to usual prescribing arm. The final health utility score was significantly higher (0.71 [0.58-0.82] vs. 0.51 [0.13-0.67] controls, p < 0.05) by improving sleepiness and depression comorbidity, with a significant reduction of 30-34% for headache, dry mouth, nervousness, and constipation. A large-scale implementation analysis could help clinical translation, together with a pharmaco-economic evaluation.

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.

Ameliorative Effect of Rice Husk Methanol Extract on Liver and Kidney Toxicities Induced by Subchronic Codeine Administration

Background and Objective. Rice husk remains a key by-product of rice milling generated in significant amount. Accumulated evidence indicates that rice husk contains numerous bioactive compounds; however, its application is limited. This study was designed to introduce an in vivo application of rice husk extract, against opioid-induced liver and kidney injuries. Codeine was considered a psychotic inducer in this study due to its global alarming misuse recently. The hepatorenal ameliorative proclivity of rice husk extract against codeine-induced toxicity on the liver and kidney in male albino Wistar rats was examined. To this effect, thirty-six (36) albino Wistar rats of weight 100-110 g were utilized and weight-matched animals placed in 6 groups of 6 rats each. After 30 days of the combined administration of codeine and the rice husk extract, the experimental animals were assayed for basic liver and renal markers such as AST, ALP, ALT, total protein, albumin, conjugated and total bilirubin, urea, creatinine, and electrolytes (sodium, potassium, chloride, and bicarbonate). Rice husks were collected from a local rice mill, and the extraction was done with methanol. Findings. Rice husk extract (RHE) significantly ameliorated the recorded hepatic damage. More so, the extract showed a significant action on the renal markers as well. A histopathology examination of the liver and kidney tissues revealed that RHE showed a hepatorenal ameliorative potential in a dose-dependent manner. Conclusion. Phytonutrient from RH possesses a healing ability against opioid-induced hepatorenal toxicity. Thus, RH is safe for human and may be adopted to obviate and manage codeine-induced hepatorenal damage or injury. Significance and Novelty. Data on the application of RHE as a phytonutrient to combat liver and kidney injuries were demonstrated. Future studies should evaluate its potential on other organs.