Update on the pharmacogenomics of pain management

Risk Factors Associated With Drug-Related Side Effects in Children: A Scoping Review

Objective. Children's vulnerability to drug-related side effects has been highlighted in several studies. However, there is no consensus on the risk factors associated with these side effects. This study aimed to investigate risk factors associated with drug-related side effects in children. Methods. This scoping review was conducted across multiple databases. The search strategy was created with a focus on drug-related side effects, as they are more predictable based on the pre-determined risk factors. Data were collected, and reported narratively. Results. The demographic, health, hospital, and drug-related risk factors may cause drug-related side effects in children. Among them, low age, sex, polypharmacy, length of hospitalization, and medications used for comorbidities may increase the risk. Conclusion. While most of the risk factors might be similar in adults and children, their impact might be different in these 2 groups. Therefore, future studies should identify more details about the impact of the risk factors in children.

Pharmacogenetic landscape of pain management variants among Mediterranean populations

Background

Chronic pain is a major socioeconomic burden in the Mediterranean region. However, we noticed an under-representation of these populations in the pharmacogenetics of pain management studies. In this context, we aimed 1) to decipher the pharmacogenetic variant landscape among Mediterranean populations compared to worldwide populations in order to identify therapeutic biomarkers for personalized pain management and 2) to better understand the biological process of pain management through in silico investigation of pharmacogenes pathways.

Materials and Methods

We collected genes and variants implicated in pain response using the Prisma guidelines from literature and PharmGK database. Next, we extracted these genes from genotyping data of 829 individuals. Then, we determined the variant distribution among the studied populations using multivariate (MDS) and admixture analysis with R and STRUCTURE software. We conducted a Chi2 test to compare the interethnic frequencies of the identified variants. We used SNPinfo web server, miRdSNP database to identify miRNA-binding sites. In addition, we investigated the functions of the identified genes and variants using pathway enrichment analysis and annotation tools. Finally, we performed docking analysis to assess the impact of variations on drug interactions.

Results

We identified 63 variants implicated in pain management. MDS analysis revealed that Mediterranean populations are genetically similar to Mexican populations and divergent from other populations. STRUCTURE analysis showed that Mediterranean populations are mainly composed of European ancestry. We highlighted differences in the minor allele frequencies of three variants (rs633, rs4680, and rs165728) located in the COMT gene. Moreover, variant annotation revealed ten variants with potential miRNA-binding sites. Finally, protein structure and docking analysis revealed that two missense variants (rs4680 and rs6267) induced a decrease in COMT protein activity and affinity for dopamine.

Conclusion

Our findings revealed that Mediterranean populations diverge from other ethnic groups. Furthermore, we emphasize the importance of pain-related pathways and miRNAs to better implement these markers as predictors of analgesic responses in the Mediterranean region.

Unraveling the Tapestry of Pain: A Comprehensive Review of Ethnic Variations, Cultural Influences, and Physiological Mechanisms in Pain Management and Perception

The medical management of pain is a nuanced challenge influenced by sociocultural, demographic, and ethical factors. This review explores the intricate interplay of these dimensions in shaping pain perception and treatment outcomes. Sociocultural elements, encompassing cultural beliefs, language, societal norms, and healing practices, significantly impact individuals' pain experiences across societies. Gender expectations further shape these experiences, influencing reporting and responses. Patient implications highlight age-related and socioeconomic disparities in pain experiences, particularly among the elderly, with challenges in managing chronic pain and socioeconomic factors affecting access to care. Healthcare provider attitudes and biases contribute to disparities in pain management across racial and ethnic groups. Ethical considerations, especially in opioid use, raise concerns about subjective judgments and potential misuse. The evolving landscape of placebo trials adds complexity, emphasizing the importance of understanding psychological and cultural factors. In conclusion, evidence-based guidelines, multidisciplinary approaches, and tailored interventions are crucial for effective pain management. By acknowledging diverse influences on pain experiences, clinicians can provide personalized care, dismantle systemic barriers, and contribute to closing knowledge gaps, impacting individual and public health, well-being, and overall quality of life.

[Design of a Tool for Patient Classification Based on Pharmacotherapeutic Attitudes]

Introduction

Perception and relief of pain exhibit variability among individuals. Age, gender, ethnicity, educational level, actual stress level, mood, or medical conditions can modify the personal interpretation of pain and responses to pharmacological treatment. These differences may play a significant role in the effects, sometimes unwanted, of analgesic treatment.

Objectives

Define patient typologies with Failed Back Syndrome regarding attitudes toward the disease, treatment, healthcare, and the follow-up they receive from their healthcare professionals. Create a tool for patient profile identification.

Materials and Methods

A clinical case series study, observational, descriptive, and cross-sectional. Study population: patients from the Pain Unit of Nuestra Señora de La Candelaria University Hospital (HUNSC) in Tenerife, conducted in three phases: collection of medical history data (F0), initial visit (F1), and personal interview (F2).

Results

Five patient typologies are obtained based on responses to 17 items. Regression equations are calculated from these responses to predict the patient type. They are grouped into "Classics," "Dependents," "Critics," "Unconscious," and "Responsible." Additionally, two tools with 17 items and another with 7 optimized items are developed to simplify the process.

Conclusions

These tools enable Community Pharmacy (CP) to identify patients based on their characteristics to direct personalized strategies for each of them.

Impact of a sensory stimulation program conducted by family members on the consciousness and pain levels of ICU patients: A mixed method study

Background

The results of several studies show the different effects of a balanced sensory stimulation program (SSP) on patients with brain injury admitted to the intensive care unit (ICU), but these effects have been less studied based on mixed and comprehensive methods.

Method

This mixed-method study involved 66 patients with brain injury admitted to the ICU who were allocated into intervention (n = 33) and control (n = 33) groups using random stratified sampling. Patients in the intervention group received a sensory stimulation program from family members for 1 h daily during ICU hospitalization, while the control group received only routine care. Patients' level of consciousness and pain intensity were measured immediately before and after the intervention using Glasgow Coma Scale (GCS) and Behavioral Pain Scale (BPS), respectively. In-depth unstructured interviews were conducted with the patients in the intervention group 3 months after discharge from the ICU. These interviews were analyzed following Graneheim and Lundman (2004) conventional content analysis method.

Results

A significant difference was found between the study groups in terms of the mean difference of GCS (P =0.001) and BPS score (P = 0.001) before and after intervention. Patients in the intervention group had a higher mean GCS and a lower mean BPS than did patients in the control group. The main themes extracted from the qualitative analysis confirmed the results obtained from the quantitative phase of the study.

Conclusion

The combination of the quantitative and qualitative findings suggested that amidst the many hardships and sufferings brain injury patients go through in the ICU, a sensory stimulation program offered by family members may have many benefits such as increased level of consciousness and reduced pain for these patients. Therefore, it is necessary to formulate a framework for this program and provide the needed facilities in order to benefit more from the capacity of such programs for ICU patients.

Genetic risk for chronic pain is associated with lower antidepressant effectiveness: Converging evidence for a depression subtype

INTRODUCTION

Chronic pain and depression are highly comorbid and difficult-to-treat disorders. We previously showed this comorbidity is associated with higher depression severity, lower antidepressant treatment effectiveness and poorer prognosis in the Australian Genetics of Depression Study.

OBJECTIVE

The current study aimed to assess whether a genetic liability to chronic pain is associated with antidepressant effectiveness over and above the effect of genetic factors for depression in a sample of 12,863 Australian Genetics of Depression Study participants.

METHODS

Polygenic risk scores were calculated using summary statistics from genome-wide association studies of multisite chronic pain and major depression. Cumulative linked regressions were employed to assess the association between polygenic risk scores and antidepressant treatment effectiveness across 10 different medications.

RESULTS

Mixed-effects logistic regressions showed that individual genetic propensity for chronic pain, but not major depression, was significantly associated with patient-reported chronic pain (Pain^PRS OR = 1.17 [1.12, 1.22]; MD^PRS OR = 1.01 [0.98, 1.06]). Significant associations were also found between lower antidepressant effectiveness and genetic risk for chronic pain or for major depression. However, a fully adjusted model showed the effect of Pain^PRS (adjOR = 0.93 [0.90, 0.96]) was independent of MD^PRS (adjOR = 0.96 [0.93, 0.99]). Sensitivity analyses were performed to assess the robustness of these results. After adjusting for depression severity measures (i.e. age of onset; number of depressive episodes; interval between age at study participation and at depression onset), the associations between Pain^PRS and patient-reported chronic pain with lower antidepressant effectiveness remained significant (0.95 [0.92, 0.98] and 0.84 [0.78, 0.90], respectively).

CONCLUSION

These results suggest genetic risk for chronic pain accounted for poorer antidepressant effectiveness, independent of the genetic risk for major depression. Our results, along with independent converging evidence from other studies, point towards a difficult-to-treat depression subtype characterised by comorbid chronic pain. This finding warrants further investigation into the implications for biologically based nosology frameworks in pain medicine and psychiatry.

The Role of Pharmacogenomics in Opioid Prescribing

Pharmacogenomics is increasingly important to guide objective, safe, and effective individualised prescribing. Personalised prescribing has revolutionised treatments in the past decade, allowing clinicians to maximise drug efficacy and minimise adverse effects based on a person’s genetic profile. Opioids, the gold standard for cancer pain relief, are among the commonest medications prescribed in palliative care practice. This narrative review examines the literature surrounding opioid pharmacogenomics and its applicability to the palliative care cancer population. There is currently limited intersection between the fields of palliative care and pharmacogenomics, but growing evidence presents a need to build linkages between the two disciplines. Pharmacogenomic evidence guiding opioid prescribing is currently available for codeine and tramadol, which relates to CYP2D6 gene variants. However, these medications are prescribed less commonly for pain in palliative care. Research is accelerating with other opioids, where oxycodone (CYP2D6) and methadone (CYP2B6, ABCB1) already have moderate evidence of an association in terms of drug metabolism and downstream analgesic response and side effects. OPRM1 and COMT are receiving increasing attention and have implications for all opioids, with changes in opioid dosage requirements observed but they have not yet been studied widely enough to be considered clinically actionable. Current evidence indicates that incorporation of pharmacogenomic testing into opioid prescribing practice should focus on the CYP2D6 gene and its actionable variants. Although opioid pharmacogenomic tests are not widely used in clinical practice, the progressively reducing costs and rapid turnover means greater accessibility and affordability to patients, and thus, clinicians will be increasingly asked to provide guidance in this area. The upsurge in pharmacogenomic research will likely discover more actionable gene variants to expand international guidelines to impact opioid prescribing. This rapidly expanding area requires consideration and monitoring by clinicians in order for key findings with clinical implications to be accessible, meaningfully interpretable and communicated.

Pharmacogenetic profiling and individualised therapy in the treatment of degenerative spinal conditions

Patients presenting with degenerative spinal changes are often poor surgical candidates due to associated co-morbidities, frailty, or sarcopenia. Additionally, surgeries of a degenerative spine can prove difficult due to the distortion of normal surgical anatomy. Therefore, many patients are managed conservatively with a variety of modalities, including over-the-counter and prescription medications. Nevertheless, several patients do not experience adequate relief from pain with analgesic medications, precipitating multiple hospital visits, and usage of resources. As a result, back pain is regarded as a major economic burden, with total costs of associated treatment exceeding $100 billion annually. Pharmacogenetics is a relatively novel method of evaluating an individual's response to analgesic medications, through analysis of germline polymorphisms. It entails obtaining a genetic sample, often via buccal swab or peripheral blood sample, and genetic analysis achieved through either polymerase chain reaction +/- Sanger sequencing, microassays, restriction length fragment polymorphism analysis, or genetic library preparation and next generation sequencing. The potential efficacy of pharmacogenetic analysis has been highlighted across several specialities to date. However, a paucity of evidence exists regarding spine surgery populations. Nevertheless, regular prospective pharmacogenetic analysis may ultimately prove beneficial when concerning degenerative spinal cohorts due to aforementioned surgical and economic considerations. The purpose of this narrative review is to outline how metaboliser profile variants affect the pharmacokinetics of specific analgesia used to treat back pain, and to discuss the current potential and limitations of employing regular pharmacogenetic analysis for spine surgery populations with degenerative conditions.

Are Opioids Contraindicated for the Palliative Care Patient with Hypotension?

Palliative care providers are frequently called to consult on patients with tenuous hemodynamics caused by an underlying serious illness. In this article, we describe a patient with end-stage renal disease who developed hypotension and severe pain due to calciphylaxis. Although opioid medications are used frequently for advanced symptom management, few studies have examined their effects on blood pressure in critically ill patients. A common concern is that opioids can worsen hypotension, and this concern can be a source of distress for providers caring for patients with unstable hemodynamics. We describe challenges encountered when trying to attend to the providers' concerns and guide shared medical decision making with the patient and family. We also summarize the current limited knowledge about the effect of opioids on hemodynamics and highlight a topic in need of further exploration.

Opioids for chronic pain management in patients with dialysis-dependent kidney failure

Chronic pain is highly prevalent among adults treated with maintenance haemodialysis (HD) and has profound negative effects. Over four decades, research has demonstrated that 50-80% of adult patients treated with HD report having pain. Half of patients with HD-dependent kidney failure (HDKF) have chronic moderate-to-severe pain, which is similar to the burden of pain in patients with cancer. However, pain management in patients with HDKF is often ineffective as most patients report that their pain is inadequately treated. Opioid analgesics are prescribed more frequently for patients receiving HD than for individuals in the general population with chronic pain, and are associated with increased morbidity, mortality and health-care resource use. Furthermore, current opioid prescribing patterns are frequently inconsistent with guideline-recommended care. Evidence for the effectiveness of opioids in pain management in general, and in patients with HDKF specifically, is lacking. Nonetheless, long-term opioid therapy has a role in the treatment of some patients when used selectively, carefully and combined with an ongoing assessment of risks and benefits. Here, we provide a comprehensive overview of the use of opioid therapy in patients with HDKF and chronic pain, including a discussion of buprenorphine, which has potential as an analgesic option for patients receiving HD owing to its unique pharmacological properties.

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.

Pharmacological Advances in Opioid Therapy: A Review of the Role of Oliceridine in Pain Management

Problems with the treatment of acute pain may arise when a patient is opioid-tolerant, such as those on chronic therapy with opioids or opiate replacement therapy, those who misuse opioids, and those who are in recovery. While some of the adverse effects of opioid medications are well known, it is also important to recognize the roles of tolerance and hyperalgesia. Oliceridine can target and modulate a novel μ-receptor pathway. The G protein-biased agonism of oliceridine allows for effective re-sensitization and desensitization of the mu-opioid receptor, which decreases the formation of opioid tolerance in patients. Oliceridine has been demonstrated to be an effective and relatively safe intravenous analgesic for the treatment of postoperative pain and is generally well tolerated with a favorable side effect profile when compared to morphine. As the prevalence of pain increases, it is becoming increasingly important to find safe and effective analgesics.

Personalized Pain Medicine: Turning Theory into Policy

: On the one hand, patients, therapists, policy-makers, business people, and health organization managers need to approach medicine from different perspectives, each perspective being appropriate for each role. On the other hand, a lack of appreciation of the perspectives of the other vested interests diminishes their effectiveness in accomplishing what their respective roles demand. In this article, we explain the main difference between these perspectives along a spectrum ranging from highly individualist to highly collectivist views of medicine. We aim to show the gap between personal (individualistic) and social (collectivist) medicine models. We then present possible ways to close this gap. We argue that these differences need to be reconciled, at least to some extent, if medicine is to evolve along with other disciplines, such as engineering, to create and implement personalized solutions to patients' pains. We conclude by proposing a framework through which patients, practitioners, health organizations, business people, and policy-makers can develop enough of a mutual understanding of each other's perspectives, problems, and solution orientations to be able to work relatively harmoniously toward the common goal of creating bespoke solutions to individuals' pains.

Ilex paraguariensis extract as an alternative to pain medications

Pain is a common and distressing symptom of many diseases and its clinical treatment generally involves analgesics and anti-inflammatory drugs. This study evaluated the toxicity of Ilex paraguariensis A. St.-Hil. (Aquifoliaceae) aqueous extract (leaves, petioles and branches) and its performance in a nociceptive response. Hepatotoxicity, psycho-stimulant test and evaluation of enzyme markers for liver damage were also tested. Chromatographic analysis by UPLC-MS demonstrated a series of isomeric monocaffeoylquinic acids, isomers of dicaffeoylquinic acid, flavonol glycosides, and saponins. Phase I and II of nociception were obtained for meloxicam, dexamethasone and aqueous Ilex paraguariensis extract. Ilex paraguariensis extract concentration was negatively correlated (R = -0.887) with alanine aminotransferase (p < 0.05) in acetaminophen-induced hepatotoxicity test, indicating hepatoprotective activity of this extract. Ilex paraguariensis extract also presented analgesic properties equivalent to drugs that already have proven efficacy. Notably, the administration of multiple doses of Ilex paraguariensis extract was considered safe from the therapeutic point of view.

Distributed sensor and actuator networks for closed-loop bioelectronic medicine

Designing implantable bioelectronic systems that continuously monitor physiological functions and simultaneously provide personalized therapeutic solutions for patients remains a persistent challenge across many applications ranging from neural systems to bioelectronic organs. Closed-loop systems typically consist of three functional blocks, namely, sensors, signal processors and actuators. An effective system, that can provide the necessary therapeutics, tailored to individual physiological factors requires a distributed network of sensors and actuators. While significant progress has been made, closed-loop systems still face many challenges before they can truly be considered as long-term solutions for many diseases. In this review, we consider three important criteria where materials play a critical role to enable implantable closed-loop systems: Specificity, Biocompatibility and Connectivity. We look at the progress made in each of these fields with respect to a specific application and outline the challenges in creating bioelectronic technologies for the future.

Therapeutic Dilemma in personalized medicine

The practice of medicine depends over a long time on identifying therapies that target an entire population. The increase in scientific knowledge over the years has led to the gradual change towards individualization and personalization of drug therapy. The hope of this change is to achieve a better clinical response to given medications and reduction of their adverse effects. Tailoring of medicine on the road of personalized medicine considers molecular and genetic mapping of the individual. However, many factors still impede the smooth application of personalized medicine and represent challenges or limitations in its achievement. In this article, we put some clinical examples that show dilemmas in the application of personalized medicine such as opioids in pain control, fluoropyrimidines in malignancy, clopidogrel as antiplatelet therapy and oral hypoglycemic drugs in Type2 diabetes in adults. Shaping the future of medicine through the application of personalized medicine for a particular patient needs to put into consideration many factors such as patient's genetic makeup and life style, pathology of the disease and dynamic changes in its course as well as interactions between administered drugs and their effects on metabolizing enzymes. We hope in the coming years, the personalized medicine will foster changes in health care system in the way not only to treat patients but also to prevent diseases.

Comorbid Chronic Pain and Depression: Shared Risk Factors and Differential Antidepressant Effectiveness

The bidirectional relationship between depression and chronic pain is well-recognized, but their clinical management remains challenging. Here we characterize the shared risk factors and outcomes for their comorbidity in the Australian Genetics of Depression cohort study (N = 13,839). Participants completed online questionnaires about chronic pain, psychiatric symptoms, comorbidities, treatment response and general health. Logistic regression models were used to examine the relationship between chronic pain and clinical and demographic factors. Cumulative linked logistic regressions assessed the effect of chronic pain on treatment response for 10 different antidepressants. Chronic pain was associated with an increased risk of depression (OR = 1.86 [1.37-2.54]), recent suicide attempt (OR = 1.88 [1.14-3.09]), higher use of tobacco (OR = 1.05 [1.02-1.09]) and misuse of painkillers (e.g., opioids; OR = 1.31 [1.06-1.62]). Participants with comorbid chronic pain and depression reported fewer functional benefits from antidepressant use and lower benefits from sertraline (OR = 0.75 [0.68-0.83]), escitalopram (OR = 0.75 [0.67-0.85]) and venlafaxine (OR = 0.78 [0.68-0.88]) when compared to participants without chronic pain. Furthermore, participants taking sertraline (OR = 0.45 [0.30-0.67]), escitalopram (OR = 0.45 [0.27-0.74]) and citalopram (OR = 0.32 [0.15-0.67]) specifically for chronic pain (among other indications) reported lower benefits compared to other participants taking these same medications but not for chronic pain. These findings reveal novel insights into the complex relationship between chronic pain and depression. Treatment response analyses indicate differential effectiveness between particular antidepressants and poorer functional outcomes for these comorbid conditions. Further examination is warranted in targeted interventional clinical trials, which also include neuroimaging genetics and pharmacogenomics protocols. This work will advance the delineation of disease risk indicators and novel aetiological pathways for therapeutic intervention in comorbid pain and depression as well as other psychiatric comorbidities.

Sauver JL. Impact of Pharmacogenomic Information on Values of Care and Quality of Life Associated with Codeine and Tramadol-Related Adverse Drug Events

Objective

To assess the potential impact of Pharmacogenomic (PGx) variation in cytochrome P450 2D6 (CYP2D6) enzyme function, using loss in quality-adjusted life years (QALYs) associated with treatment problems, and the willingness to pay to avoid treatment problems from patients’ and payers’ perspectives.

Patients and Methods

The study included patients prescribed tramadol or codeine, or both, between January 1, 2005, and December 31, 2017. Demographic information and adverse drug events, including adverse drug events and poor pain control, were collected from the electronic health records using natural language processing techniques and review by trained abstractors. Patients’ willingness to pay and QALY estimates were based on comprehensive literature review. The CYP2D6 phenotypes were divided into 4 groups: ultra-rapid metabolizers, normal metabolizers, intermediate metabolizers, and poor metabolizers.

Results

Among the 2860 identified patients, 63 (2%) were ultrarapid metabolizers, 1449 (50%) were normal metabolizers, 1155 (40%) were intermediate metabolizers, and 193 (7%) were poor metabolizers. The patients’ average estimated willingness-to-pay value to avoid treatment problems was $23 per month; poor metabolizers developed problems with the highest estimated willingness-to-pay value ($32 per month). The mean QALY loss among all patients was 0.024 QALYs (8.8 healthy days); poor metabolizers had the highest loss (0.027 QALYs, 9.9 healthy days).

Conclusion

Patients with various phenotypes developed different treatment problem profiles. Poor CYP2D6 metabolizers developed problems with highest willingness to pay, and they might potentially benefit most from PGx-guided treatment and problem prevention.

Evaluation of Phenotypic and Genotypic Variations of Drug Metabolising Enzymes and Transporters in Chronic Pain Patients Facing Adverse Drug Reactions or Non-Response to Analgesics: A Retrospective Study

This retrospective study evaluates the link between an adverse drug reaction (ADR) or a non-response to treatment and cytochromes P450 (CYP), P-glycoprotein (P-gp) or catechol-O-methyltransferase (COMT) activity in patients taking analgesic drugs for chronic pain. Patients referred to a pain center for an ADR or a non-response to an analgesic drug between January 2005 and November 2014 were included. The genotype and/or phenotype was obtained for assessment of the CYPs, P-gp or COMT activities. The relation between the event and the result of the genotype and/or phenotype was evaluated using a semi-quantitative scale. Our analysis included 243 individual genotypic and/or phenotypic explorations. Genotypes/phenotypes were mainly assessed because of an ADR (n = 145, 59.7%), and the majority of clinical situations were observed with prodrug opioids (n = 148, 60.9%). The probability of a link between an ADR or a non-response and the genotypic/phenotypic status of the patient was evaluated as intermediate to high in 40% and 28.2% of all cases, respectively. The drugs in which the probability of an association was the strongest were the prodrug opioids, with an intermediate to high link in 45.6% of the cases for occurrence of ADRs and 36.0% of the cases for non-response. This study shows that the genotypic and phenotypic approach is useful to understand ADRs or therapeutic resistance to a usual therapeutic dosage, and can be part of the evaluation of chronic pain patients.

CYP2D6 Expression in Veterans Experiencing Opioid Overdose: A Postmortem Review

Purpose

The purpose is to characterize the CYP2D6 genotype and predict the phenotype of decedents of opioid overdose to determine if the ultrarapid (UM) phenotype is over-represented in opioid overdose deaths. CYP2D6 is the enzyme responsible for metabolism of various opioids implicated in overdose. The UM group may be at greater risk for overdose due to the rapid metabolism of hydrocodone, oxycodone, or tramadol to more active/potent metabolites than their peers with (poor) PM, (intermediate) IM, or (extensive) EM metabolic phenotypes.

Patients and Methods

Blood samples obtained during autopsy following an opioid overdose from 75 US military veteran decedents prescribed hydrocodone, oxycodone, or tramadol from one VA medical center were analyzed. DNA extraction, CYP2D6 genotyping, and copy number variation (CNV) testing were performed using the iPLEX^® genotyping assay and MassARRAY. Phenotype prediction was based on Clinical Pharmacogenetics Implementation Consortium (CPIC) recommendations. Toxicology results were obtained from Medical Examiner reports of the deceased. Prescription medication information was extracted from archived medical records.

Results

The majority of the sample had a phenotype of EM metabolizer (75%), with 7% of the total sample having a UM metabolizer phenotype. In addition to hydrocodone, oxycodone, and tramadol (found in 41% of opioid positive samples), other opioids found in toxicology tests included diacetylmorphine, fentanyl, buprenorphine, and methadone. Two or more substances, including alcohol, benzodiazepines, and other potentially sedating medications, were found in nearly half of the opioid positive toxicology samples.

Conclusion

In this study, 7% of veteran decedents of opioid overdose had CYP2D6 UM metabolic phenotype. The small sample size precludes a conclusion that the frequency of UM phenotype is greater than expected in North American Caucasian groups. The findings in this study do not support the hypothesis that the UM phenotype is over-represented in opioid overdose.

Pharmacogenomics of Pain Management: The Impact of Specific Biological Polymorphisms on Drugs and Metabolism

PURPOSE OF REVIEW

Pain is multifactorial and complex, often with a genetic component. Pharmacogenomics is a relative new field, which allows for the development of a truly unique and personalized therapeutic approach in the treatment of pain.

RECENT FINDINGS

Until recently, drug mechanisms in humans were determined by testing that drug in a population and calculating response averages. However, some patients will inevitably fall outside of those averages, and it is nearly impossible to predict who those outliers might be. Pharmacogenetics considers a patient's unique genetic information and allows for anticipation of that individual's response to medication. Pharmacogenomic testing is steadily making progress in the management of pain by being able to identify individual differences in the perception of pain and susceptibility and sensitivity to drugs based on genetic markers. This has a huge potential to increase efficacy and reduce the incidence of iatrogenic drug dependence and addiction. The streamlining of relevant polymorphisms of genes encoding receptors, transporters, and drug-metabolizing enzymes influencing the pain phenotype can be an important guide to develop safe new strategies and approaches to personalized pain management. Additionally, some challenges still prevail and preclude adoption of pharmacogenomic testing universally. These include lack of knowledge about pharmacogenomic testing, inadequate standardization of the process of data handling, questionable benefits about the clinical and financial aspects of pharmacogenomic testing-guided therapy, discrepancies in clinical evidence supporting these tests, and doubtful reimbursement of the tests by health insurance agencies.

Epidural Analgesia With Sufentanil in Relation to OPRM1 and ABCB1 Polymorphisms

The aim of this study was to evaluate the association between OPRM1 and ABCB1 polymorphisms on pain relief with epidural sufentanil in 69 patients after rectosigma resection for cancer. The median number of injections (SD) 2.31 (1.36), IQR=1, required by 118AA subjects was significantly lower in comparison with 118AG group 5.25 (3.13), IQR=6.5, (χ2=9.75, p=0.001); correspondingly median drug consumption of 1.16 (0.79), IQR=1.083, defined daily doses (DDD) was significantly less in the 118AA group in comparison with 2.14 (1.17), IQR=2.23, DDD in 118AG subjects, (χ2=7.00, p=0.008). Opioid-induced adverse effects were observed in 15 % and 33 % of patients in 118AA and 118AG groups, respectively (χ2=8.16, p=0.004). The median number of injections (SD) required by women and men was 3.30 (2.16), IQR=2, and 2.80 (1.59), IQR=1, respectively (χ2=6.25, p=0.012). Opioid-induced adverse effects were observed in 26 % and 12 % of women and men, respectively (χ2=5.49, p=0.011). Heterozygotes of OPRM1 polymorphism and women were more difficult to treat subpopulations that required higher doses of rescue analgesic medication and suffered more adverse effects.

Molecular Basis of Cancer Pain Management: An Updated Review

Pain can have a significantly negative impact on the quality of life of patients. Therefore, patients may resort to analgesics to relieve the pain. The struggle to manage pain in cancer patients effectively and safely has long been an issue in medicine. Analgesics are the mainstay treatment for pain management as they act through various methods on the peripheral and central pain pathways. However, the variability in the patient genotypes may influence a drug response and adverse drug effects that follow through. This review summarizes the observed effects of analgesics on UDP-glucuronosyl (UGT) 2B7 isoenzyme, cytochrome P450 (CYP) 2D6, μ-opioid receptor μ 1 (OPRM1), efflux transporter P-glycoprotein (P-gp) and ATP-binding cassette B1 ABCB1/multiple drug resistance 1 (MDR1) polymorphisms on the mechanism of action of these drugs in managing pain in cancer. Furthermore, this review article also discusses the responses and adverse effects caused by analgesic drugs in cancer pain management, due to the inter-individual variability in their genomes.