Genetic Testing for Opioid Pain Management: A Primer

Safety, Tolerability, and Dose-Limiting Toxicity of Lacosamide in Patients With Painful Chronic Pancreatitis: Protocol for a Phase 1 Clinical Trial to Determine Safety and Identify Side Effects

BACKGROUND

Chronic abdominal pain is the hallmark symptom of chronic pancreatitis (CP), with 50% to 80% of patients seeking medical attention for pain control. Although several management options are available, outcomes are often disappointing, and opioids remain a mainstay of therapy. Opioid-induced hyperalgesia is a phenomenon resulting in dose escalation, which may occur partly because of the effects of opioids on voltage-gated sodium channels associated with pain. Preclinical observations demonstrate that the combination of an opioid and the antiseizure drug lacosamide diminishes opioid-induced hyperalgesia and improves pain control.

OBJECTIVE

In this phase 1 trial, we aim to determine the safety, tolerability, and dose-limiting toxicity of adding lacosamide to opioids for the treatment of painful CP and assess the feasibility of performance of a pilot study of adding lacosamide to opioid therapy in patients with CP. As an exploratory aim, we will assess the efficacy of adding lacosamide to opioid therapy in patients with painful CP.

METHODS

Using the Bayesian optimal interval design, we will conduct a dose-escalation trial of adding lacosamide to opioid therapy in patients with painful CP enrolled in cohorts of size 3. The initial dose will be 50 mg taken orally twice a day, followed by incremental increases to a maximum dose of 400 mg/day, with lacosamide administered for 7 days at each dose level. Adverse events will be documented according to Common Terminology Criteria for Adverse Events (version 5.0).

RESULTS

As of December 2023, we have currently enrolled 6 participants. The minimum number of participants to be enrolled is 12 with a maximum of 24. We expect to publish the results by March 2025.

CONCLUSIONS

This trial will test the feasibility of the study design and provide reassurance regarding the tolerability and safety of opioids in treating painful CP. It is anticipated that lacosamide will prove to be safe and well tolerated, supporting a subsequent phase 2 trial assessing the efficacy of lacosamide+opioid therapy in patients with painful CP, and that lacosamide combined with opiates will lower the opioid dose necessary for pain relief and improve the safety profile of opioid use in treating painful CP.

TRIAL REGISTRATION

Clinicaltrials.gov NCT05603702; https://clinicaltrials.gov/study/NCT05603702.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/50513.

Maximizing patient safety when prescribing opioids for pain management

ABSTRACT

Cytochrome P450 enzyme metabolism is altered by environmental and genetic factors, which can affect the efficacy and safety of opioids. This article describes CYP polymorphisms and how pharmacogenetic testing could be used to help clinicians make safer decisions about opioid use in patients.

Endogenous opioid systems alterations in pain and opioid use disorder

Decades of research advances have established a central role for endogenous opioid systems in regulating reward processing, mood, motivation, learning and memory, gastrointestinal function, and pain relief. Endogenous opioid systems are present ubiquitously throughout the central and peripheral nervous system. They are composed of four families, namely the μ (MOPR), κ (KOPR), δ (DOPR), and nociceptin/orphanin FQ (NOPR) opioid receptors systems. These receptors signal through the action of their endogenous opioid peptides β-endorphins, dynorphins, enkephalins, and nociceptins, respectfully, to maintain homeostasis under normal physiological states. Due to their prominent role in pain regulation, exogenous opioids-primarily targeting the MOPR, have been historically used in medicine as analgesics, but their ability to produce euphoric effects also present high risks for abuse. The ability of pain and opioid use to perturb endogenous opioid system function, particularly within the central nervous system, may increase the likelihood of developing opioid use disorder (OUD). Today, the opioid crisis represents a major social, economic, and public health concern. In this review, we summarize the current state of the literature on the function, expression, pharmacology, and regulation of endogenous opioid systems in pain. Additionally, we discuss the adaptations in the endogenous opioid systems upon use of exogenous opioids which contribute to the development of OUD. Finally, we describe the intricate relationship between pain, endogenous opioid systems, and the proclivity for opioid misuse, as well as potential advances in generating safer and more efficient pain therapies.

Opioid-Related Genetic Polymorphisms of Cytochrome P450 Enzymes after Total Joint Arthroplasty: A Focus on Drug-Drug-Gene Interaction with Commonly Coprescribed Medications

Pharmacogenomic testing, together with the early detection of drug-drug-gene interactions (DDGI) before initiating opioids, can improve the selection of dosage and reduce the risk of adverse drug interactions and therapeutic failures following Total Joint Arthroplasty. The variants of CYP genes can mediate DDGI. Orthopedic surgeons should become familiar with the genetic aspect of opioid use and abuse, as well as the influence of the patient genetic makeup in opioid selection and response, and polymorphic variants in pain modulation.

Pharmacogenetic Gene-Drug Associations in Pediatric Burn and Surgery Patients

Management of critically ill patients requires simultaneous administration of many medications. Treatment for patient comorbidities may lead to drug-drug interactions which decrease drug efficacy or increase adverse reactions. Current practices rely on a one-size-fits-all dosing approach. Pharmacogenetic testing is generally reserved for addressing problems rather than used proactively to optimize care. We hypothesized that burn and surgery patients will have one or more genetic variants in drug metabolizing pathways used by one or more medications administered during the patient's hospitalization. The aim of this study was to determine the frequency of variants with abnormal function in the primary drug pathways and identify which medications may be impacted. Genetic (19 whole exome and 11 whole genome) and medication data from 30 pediatric burn and surgery patients were analyzed to identify pharmacogene-drug associations. Nineteen patients were identified with predicted altered function in one or more of the following genes: CYP2C9, CYP2C19, CYP2D6, and CYP3A4. The majority had decreased function, except for several patients with CYP2C19 rapid or ultrarapid variants. Some drugs administered during hospitalization that rely on these pathways include hydrocodone, oxycodone, methadone, ibuprofen, ketorolac, celecoxib, diazepam, famotidine, diphenhydramine, and glycopyrrolate. Approximately one-third of the patients tested had functionally impactful genotypes in each of the primary drug metabolizing pathways. This study suggests that genetic variants may in part explain the vast variability in drug efficacy and suggests that future pharmacogenetics research may optimize dosing regimens.

Effects of Pharmacogenomic Testing in Clinical Pain Management: Retrospective Study

BACKGROUND

The availability of pharmacogenomic (PGx) methods to determine the right drug and dosage for individualized patient treatment has increased over the past decade. Adoption of the resulting PGx reports in a clinical setting and monitoring of clinical outcomes is a challenging and long-term commitment.

OBJECTIVE

This study summarizes an extended PGx deep sequencing panel intended for medication dosing and prescription guidance newly adopted in a pain management clinic. The primary outcome of this retrospective study reports the number of cases and types of drugs covered, for which PGx data appears to have assisted in optimal drug prescription and dosing.

METHODS

A PGx panel is described, encompassing 23 genes and 141 single-nucleotide polymorphisms or indels, combined with PGx dosing guidance and drug-gene interaction (DGI) and drug-drug interaction (DDI) reporting to prevent adverse drug reactions (ADRs). During a 2-year period, patients (N=171) were monitored in a pain management clinic. Urine toxicology, PGx reports, and progress notes were studied retrospectively for changes in prescription regimens before and after the PGx report was made available to the provider. An additional algorithm provided DGIs and DDIs to prevent ADRs.

RESULTS

Among patient PGx reports with medication lists provided (n=146), 57.5% (n=84) showed one or more moderate and 5.5% (n=8) at least one serious PGx interaction. A total of 96 (65.8%) patients showed at least one moderate and 15.1% (n=22) one or more serious DGIs or DDIs. A significant number of active changes in prescriptions based on the 102 PGx/DGI/DDI report results provided was observed for 85 (83.3%) patients for which a specific drug was either discontinued or switched within the defined drug classes of the report, or a new drug was added.

CONCLUSIONS

Preventative action was observed for all serious interactions, and only moderate interactions were tolerated for the lack of other alternatives. This study demonstrates the application of an extended PGx panel combined with a customized informational report to prevent ADRs and improve patient care.

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.

Understanding the Psychological, Physiological, and Genetic Factors Affecting Precision Pain Medicine: A Narrative Review

PURPOSE

Precision pain medicine focuses on employing methods to assess each patient individually, identify their risk profile for disproportionate pain and/or the development of chronic pain, and optimize therapeutic strategies to target specific pathological processes underlying chronic pain. This review aims to provide a concise summary of the current body of knowledge regarding psychological, physiological, and genetic determinants of chronic pain related to precision pain medicine.

METHODS

Following the Scale for the Assessment of Narrative Review Articles (SANRA) criteria, we employed PubMed/Medline to identify relevant articles using primary database search terms to query articles such as: precision medicine, non-modifiable factors, pain, anesthesiology, quantitative sensory testing, genetics, pain medicine, and psychological.

RESULTS

Precision pain medicine provides an opportunity to identify populations at risk, develop personalized treatment strategies, and reduce side effects and cost through elimination of ineffective treatment strategies. As in other complex chronic health conditions, there are two broad categories that contribute to chronic pain risk: modifiable and non-modifiable patient factors. This review focuses on three primary determinants of health, representing both modifiable and non-modifiable factors, that may contribute to a patient's profile for risk of developing pain and most effective management strategies: psychological, physiological, and genetic factors.

CONCLUSION

Consideration of these three domains is already being integrated into patient care in other specialties, but by understanding the role they play in development and maintenance of chronic pain, we can begin to implement both precision and personalized treatment regimens.

Opioids and Chronic Pain: An Analytic Review of the Clinical Evidence

We conducted an analytic review of the clinical scientific literature bearing on the use of opioids for treatment of chronic non-cancer pain in the United States. There is substantial, albeit not definitive, scientific evidence of the effectiveness of opioids in treating pain and of high variability in opioid dose requirements and side effects. The estimated risk of death from opioid treatment involving doses above 100 MMED is ~0.25%/year. Multiple large studies refute the concept that short-term use of opioids to treat acute pain predisposes to development of opioid use disorder. The prevalence of opioid use disorder associated with prescription opioids is likely <3%. Morbidity, mortality, and financial costs of inadequate treatment of the 18 million Americans with moderate to severe chronic pain are high. Because of the absence of comparative effectiveness studies, there are no scientific grounds for considering alternative non-pharmacologic treatments as an adequate substitute for opioid therapy but these treatments might serve to augment opioid therapy, thereby reducing dosage. There are reasons to question the ostensible risks of co-prescription of opioids and benzodiazepines. As the causes of the opioid crisis have come into focus, it has become clear that the crisis resides predominantly in the streets and that efforts to curtail it by constraining opioid treatment in the clinic are unlikely to succeed.

The effect of CYP2D6 and CYP2C9 gene polymorphisms on the efficacy and safety of the combination of tramadol and ketorolac used for postoperative pain management in patients after video laparoscopic cholecystectomy

OBJECTIVES

One of the key components of ERAS is adequate pain control in the postoperative period. There are no rational schemes for postoperative pain relief. At the same time, adequate postoperative pain relief promotes early activation and early rehabilitation of patients and shortens the duration of the postoperative stay, and does not cause postoperative complications associated with analgesia (weakness, intestinal paresis, nausea and vomiting). The aims of the present study are to assess the possible association of CYP2D6 and CYP2C9 polymorphisms with the efficacy and safety of tramadol and ketorolac in postoperative pain.

METHODS

A total of 107 patients were genotyped for CYP2D6 and CYP2C9 polymorphisms. All patients underwent laparoscopic cholecystectomy. Postoperative pain relief was carried out with ketorolac and tramadol. Postoperative pain syndrome was assessed using a visual analogue scale and McGill pain questionnaire. The profile of side effects was assessed by the dynamics of red blood counts as a possible trigger for the development of gastrointestinal bleeding according to the method of global assessment of triggers.

RESULTS

Pain was statistically significantly lower in CYP2C9*2 carriers, according to visual analogue scale (VAS): after 12 h - by 1.5 (p=0.002); after 24 h - by 1.1 (p=0.012); after 36 h - by 1.05 (p=0.004); after 48 h - by 0.7 (p=0.026). In CYP2C9*3 carriers the results were not statistically significant. In carriers of CYP2D6*4 pain syndromes were higher at all-time intervals, but statistically reliable results were obtained only after 2 h - by 1.01 (p=0.054) and after 24 h - by 0.8 (p=0.035). The profile of adverse reactions for NSAIDs was evaluated by the dynamics of hemoglobin and erythrocyte indices. A more pronounced decrease in the relative difference in hemoglobin levels was noted in CYP2C9*2 and CYP2C9*3 polymorphism carriers - by 1.7 (p=0.00268) and-by 2.2 (p=0.000143), respectively.

CONCLUSIONS

CYP2D6 and CYP2C9 can predict analgesic effectiveness of tramadol and ketorolac. CYP2C9 can predict the risk of gastrointestinal bleeding, including those hidden to ketorolac.

The effect of CYP2D6 and CYP2C9 gene polymorphisms on the efficacy and safety of the combination of tramadol and ketorolac used for postoperative pain management in patients after video laparoscopic cholecystectomy

OBJECTIVES

One of the key components of ERAS is adequate pain control in the postoperative period. There are no rational schemes for postoperative pain relief. At the same time, adequate postoperative pain relief promotes early activation and early rehabilitation of patients and shortens the duration of the postoperative stay, and does not cause postoperative complications associated with analgesia (weakness, intestinal paresis, nausea and vomiting). The aims of the present study are to assess the possible association of CYP2D6 and CYP2C9 polymorphisms with the efficacy and safety of tramadol and ketorolac in postoperative pain.

METHODS

A total of 107 patients were genotyped for CYP2D6 and CYP2C9 polymorphisms. All patients underwent laparoscopic cholecystectomy. Postoperative pain relief was carried out with ketorolac and tramadol. Postoperative pain syndrome was assessed using a visual analogue scale and McGill pain questionnaire. The profile of side effects was assessed by the dynamics of red blood counts as a possible trigger for the development of gastrointestinal bleeding according to the method of global assessment of triggers.

RESULTS

Pain was statistically significantly lower in CYP2C9*2 carriers, according to visual analogue scale (VAS): after 12 h - by 1.5 (p=0.002); after 24 h - by 1.1 (p=0.012); after 36 h - by 1.05 (p=0.004); after 48 h - by 0.7 (p=0.026). In CYP2C9*3 carriers the results were not statistically significant. In carriers of CYP2D6*4 pain syndromes were higher at all-time intervals, but statistically reliable results were obtained only after 2 h - by 1.01 (p=0.054) and after 24 h - by 0.8 (p=0.035). The profile of adverse reactions for NSAIDs was evaluated by the dynamics of hemoglobin and erythrocyte indices. A more pronounced decrease in the relative difference in hemoglobin levels was noted in CYP2C9*2 and CYP2C9*3 polymorphism carriers - by 1.7 (p=0.00268) and-by 2.2 (p=0.000143), respectively.

CONCLUSIONS

CYP2D6 and CYP2C9 can predict analgesic effectiveness of tramadol and ketorolac. CYP2C9 can predict the risk of gastrointestinal bleeding, including those hidden to ketorolac.

European* clinical practice recommendations on opioids for chronic noncancer pain - Part 1: Role of opioids in the management of chronic noncancer pain

BACKGROUND

Opioid use for chronic non-cancer pain (CNCP) is complex. In the absence of pan-European guidance on this issue, a position paper was commissioned by the European Pain Federation (EFIC).

METHODS

The clinical practice recommendations were developed by eight scientific societies and one patient self-help organization under the coordination of EFIC. A systematic literature search in MEDLINE (up until January 2020) was performed. Two categories of guidance are given: Evidence-based recommendations (supported by evidence from systematic reviews of randomized controlled trials or of observational studies) and Good Clinical Practice (GCP) statements (supported either by indirect evidence or by case-series, case-control studies and clinical experience). The GRADE system was applied to move from evidence to recommendations. The recommendations and GCP statements were developed by a multiprofessional task force (including nursing, service users, physicians, physiotherapy and psychology) and formal multistep procedures to reach a set of consensus recommendations. The clinical practice recommendations were reviewed by five external reviewers from North America and Europe and were also posted for public comment.

RESULTS

The key clinical practice recommendations suggest: (a) first optimizing established non-pharmacological treatments and non-opioid analgesics and (b) considering opioid treatment if established non-pharmacological treatments or non-opioid analgesics are not effective and/or not tolerated and/or contraindicated. Evidence- and clinical consensus-based potential indications and contraindications for opioid treatment are presented. Eighteen GCP recommendations give guidance regarding clinical evaluation, as well as opioid treatment assessment, monitoring, continuation and discontinuation.

CONCLUSIONS

Opioids remain a treatment option for some selected patients with CNCP under careful surveillance.

SIGNIFICANCE

In chronic pain, opioids are neither a universal cure nor a universally dangerous weapon. They should only be used for some selected chronic noncancer pain syndromes if established non-pharmacological and pharmacological treatment options have failed in supervised pain patients as part of a comprehensive, multi-modal, multi-disciplinary approach to treatment. In this context alone, opioid therapy can be a useful tool in achieving and maintaining an optimal level of pain control in some patients.

Pharmacogenetic testing: Clinical integration and application for chronic pain management

ABSTRACT

NPs commonly prescribe pharmaceutical therapies such as opiates, antidepressants, and/or other analgesics to improve the health and well-being of patients experiencing chronic pain. This article provides NPs with pharmacogenetic testing knowledge, such as readiness for clinical implementation, considerations for choosing a testing service, and testing costs for chronic pain management.

Pharmacogenomics and prescription opioid use

Genome-wide association studies and candidate gene findings suggest that genetic approaches may help in choosing the most appropriate drug and dosage, while preventing adverse drug reactions. This is the field that addresses precision medicine: to evaluate variations in the DNA sequence that could be responsible for different individual analgesic response. We review potential gene biomarkers with best overall convergent functional evidence, for opioid use, in pain management. Polymorphisms can modify pharmacodynamics (i.e., mu opioid receptor, OPRM1) and pharmacokinetics (i.e., CYP2D6 phenotypes) pathways altering opioid effectiveness, consumption, side effects or additionally, prescription opioid use dependence vulnerability. This review provides a summary of these candidate variants for the translation of genotype into clinically useful information in pain medicine.

Design and conduct of confirmatory chronic pain clinical trials

The purpose of this article is to provide readers with a basis for understanding the emerging science of clinical trials and to provide a set of practical, evidence-based suggestions for designing and executing confirmatory clinical trials in a manner that minimizes measurement error. The most important step in creating a mindset of quality clinical research is to abandon the antiquated concept that clinical trials are a method for capturing data from clinical practice and shifting to a concept of the clinical trial as a measurement system, consisting of an interconnected set of processes, each of which must be in calibration for the trial to generate an accurate and reliable estimate of the efficacy (and safety) of a given treatment. The status quo of inaccurate, unreliable, and protracted clinical trials is unacceptable and unsustainable. This article gathers aspects of study design and conduct under a single broad umbrella of techniques available to improve the accuracy and reliability of confirmatory clinical trials across traditional domain boundaries.

Nature of adverse events with opioids in hospitalised patients: a post-hoc analysis of three patient record review studies

OBJECTIVE

Opioids are increasingly prescribed and frequently involved in adverse drug events (ADEs). The underlying nature of opioid-related ADEs (ORADEs) is however understudied. This hampers our understanding of risks related to opioid use during hospitalisation and when designing interventions. Therefore, we provided a description of the nature of ORADEs.

DESIGN

A post-hoc analysis of data collected during three retrospective patient record review studies (in 2008, 2011/2012 and 2015/2016).

SETTING

The three record review studies were conducted in 32 Dutch hospitals.

PARTICIPANTS

A total of 10 917 patient records were assessed by trained nurses and physicians.

OUTCOME MEASURES

Per identified ORADE, we described preventability, type of medication error, attributable factors and type of opioids involved. Moreover, the characteristics of preventable and non-preventable ORADEs were compared to identify risk factors.

RESULTS

Out of 10 917 patient records, 357 ADEs were identified, of which 28 (8%) involved opioids. Eleven ORADEs were assessed as preventable. Of these, 10 were caused by dosing errors and 4 probably contributed to patients' death. Attributable factors identified were mainly on patient and organisational levels. Morphine and oxycodone were the most frequently involved opioids. The risk for ORADEs was higher in elderly patients.

CONCLUSIONS

Only 8% of ADEs identified in our sample were related to opioids. Although the frequency is low, the risk of serious consequences is high. We recommend to use our findings to increase awareness among physicians and nurses. Future interventions should focus on safe dosing of opioids when prescribing and administering, especially in elderly patients.

Pain pharmacogenetics

Pain is a significant problem in medicine. The use of PGx markers to personalize postoperative analgesia can increase its effectiveness and avoid undesirable reactions. This article describes the mechanisms of nociception and antinociception and shows the pathophysiological mechanisms of pain in the human body. The main subject of this article is pharmacogenetic approach to the selection of anesthetics. Current review presents data for local and general anesthetics, opioids, and non-steroidal anti-inflammatory drugs. None of the anesthetics currently has clinical guidelines for pharmacogenetic testing. This literature review summarizes the results of original research available, to date, and draws attention to this area.

Genetics and Opioids: Towards More Appropriate Prescription in Cancer Pain

Opioids are extensively used in patients with cancer pain; despite their efficacy, several patients can experience ineffective analgesia and/or side effects. Pharmacogenetics is a new approach to drug prescription based on the “personalized-medicine” concept, i.e., the ability of tailoring treatments to each individual’s genetic/genomic profile. Pharmacogenetics aims to identify specific genetic variants that influence pharmacokinetics and pharmacodynamics of drugs, better determining their effectiveness/safety profile. Opioid response is a complex scenario, but some gene variants have shown a correlation with pain sensitivity, as well as with opioid metabolism and clinical efficacy/adverse events. Although questions remain unanswered, some of these gene variants may already be used to identify specific patients’ phenotypes that are more prone to experience better clinical response (i.e., better analgesia and/or less adverse events). Once adopted, this approach to opioid prescription may improve a patient’s outcome. This review summarizes the available data on genetic variants and opioid response: we will focus on basic pharmacogenetic and its impact in the clinical scenario discussing how they may lead to more appropriate opioid prescription in cancer patients.

What the lab can and cannot do: clinical interpretation of drug testing results

Urine drug testing is one of the objective tools available to assess adherence. To monitor adherence, quantitative urinary results can assist in differentiating "new" drug use from "previous" (historical) drug use. "Spikes" in urinary concentration can assist in identifying patterns of drug use. Coupled chromatographic-mass spectrometric methods are capable of identifying very small amounts of analyte and can make clinical interpretation rather challenging, specifically for drugs that have a longer half-life. Polypharmacy is common in treatment and rehabilitation programs because of co-morbidities. Medications prescribed for comorbidities can cause drug-drug interaction and phenoconversion of genotypic extensive metabolizers into phenotypic poor metabolizers of the treatment drug. This can have significant impact on both pharmacokinetic (PK) and pharmacodynamic properties of the treatment drug. Therapeutic drug monitoring (TDM) coupled with PKs can assist in interpreting the effects of phenoconversion. TDM-PKs reflects the cumulative effects of pathophysiological changes in the patient as well as drug-drug interactions and should be considered for treatment medications/drugs used to manage pain and treat substance abuse. Since only a few enzyme immunoassays for TDM are available, this is a unique opportunity for clinical laboratory scientists to develop TDM-PK protocols that can have a significant impact on patient care and personalized medicine. Interpretation of drug screening results should be done with caution while considering pharmacological properties and the presence or absence of the parent drug and its metabolites. The objective of this manuscript is to review and address the variables that influence interpretation of different drugs analyzed from a rehabilitation and treatment programs perspective.

Opioids: Pharmacology, Physiology, and Clinical Implications in Pain Medicine

Opioid receptors and opioid agonists are widespread throughout nature. Endogenous opioids mediate complex functions in animals and in humans. The opioid system in humans plays a central role in pain control and is a key mediator of hedonic homeostasis, mood, and well-being. This system also regulates responses to stress and several peripheral physiologic functions, including respiratory, gastrointestinal, endocrine, and immune systems. This article provides an overview of the basic physiology of opioids, reviews opioid pharmacology, and attempts to address several issues of current importance in the management of patients with established long-term opioid therapy.

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.

Assessing the contribution of opioid- and dopamine-related genetic polymorphisms to the abuse liability of oxycodone

BACKGROUND

Attempts to identify opioid users at increased risk of escalating to opioid use disorder have had limited success. Data from a variety of sources suggest that genetic variation may mediate the subjective response to opioid drugs, and therefore contribute to their abuse potential. The goal of the current study was to observe the relationship between select genetic polymorphisms and the subjective effects of oxycodone under controlled clinical laboratory conditions.

METHODS

Non-dependent, volunteers with some history of prescription opioid exposure (N = 36) provided a blood sample for analyses of variations in the genes that encode for the μ-, κ- and δ-opioid receptors, and the dopamine metabolizing enzyme, catechol-O-methyltransferase (COMT). Participants then completed a single laboratory test session to evaluate the subjective and analgesic effects of oral oxycodone (0, 10, and 20 mg, cumulative dose = 30 mg).

RESULTS

Oxycodone produced typical μ-opioid receptor agonist effects, such as miosis, and decreased pain perception. Oxycodone also produced dose-dependent increases in positive subjective responses such as: drug "Liking" and "Good Effect." Genetic variants in the μ- (rs6848893) and δ-opioid receptor (rs581111) influenced the responses to oxycodone administration. Additionally, self-reported "Stimulated" effects of oxycodone varied significantly as a function of COMT rs4680 genotype.

DISCUSSION

The current study shows that the euphoric and stimulating effects of oxycodone can vary as a function of genetic variation. Though the relationship between the stimulating effects of opioids and their abuse liability is not well established, we know that the ability of opioids to provide intense feelings of pleasure is a significant motivator for continued use. If replicated, specific genetic variants may be useful in predicting who is at increased risk of developing maladaptive patterns of use following medical exposure to opioid analgesics.

Opioid e-prescribing trends at discharge in a large pediatric health system

OBJECTIVE

Legitimate opioid prescriptions have been identified as a risk factor for opioid misuse in pediatric patients. In 2014, Pennsylvania legislation expanded a prescription drug monitoring program (PDMP) to curb inappropriate controlled substance prescriptions. The authors' objective was to describe recent opioid prescribing trends at a large, pediatric health system situated in a region with one of the highest opioid-related death rates in the United States and examine the impact of the PDMP on prescribing trends.

DESIGN

Quasi-experimental assessment of trends of opioid e-prescriptions, from 2012 to 2017. Multivariable Poisson segmented regression examined the effect of the PDMP. Period prevalence comparison of opioid e-prescriptions across the care continuum in 2016.

RESULTS

There were 62,661 opioid e-prescriptions identified during the study period. Combination opioid/non-opioid prescriptions decreased, while oxycodone prescriptions increased. Seasonal variation was evident. Of 110,884 inpatient encounters, multivariable regression demonstrated lower odds of an opioid being prescribed at discharge per month of the study period (p < 0.001) and a significant interaction between passage of the PDMP legislation and time (p = 0.03). Black patients had lower odds of receiving an opioid at discharge compared to white patients. Inpatients had significantly greater odds of receiving an opioid compared to emergency department (Prevalence Odds Ratio 7.1 [95% confidence interval: 6.9-7.3]; p < 0.001) and outpatient (398.9 [355.5-447.5]; p < 0.001) encounters.

CONCLUSION

In a large pediatric health system, oxycodone has emerged as the most commonly prescribed opioid in recent years. Early evidence indicates that a state-run drug monitoring program is associated with reduced opioid prescribing. Additional study is necessary to examine the relationship between opioid prescriptions and race.

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.

Opioid Use in the Postoperative Arena: Global Reduction in Opioids After Surgery Through Enhanced Recovery and Gynecologic Surgery

Enhanced recovery programs aim to reduce surgical stress to improve the patient perioperative experience. Through a combination of multimodal analgesia and maintaining a physiological state, postoperative recovery is improved. Many analgesic adjuncts are available that improve postoperative pain control and limit opioid analgesia requirements. Adjuncts are often used in combination, but different interventions may be incorporated for patient-specific and procedure-specific needs. Postoperative pain control can be optimized by continuing nonopioid adjuncts, and prescribing opioid analgesia to address breakthrough pain. Prescribing practices should balance optimizing pain relief, minimizing the risk of chronic pain, while limiting the potential for opioid misuse.

Treating chronic pain and opioid misuse disorder among underserved populations in Colorado

The increased use of prescription opioids has resulted in widespread misuse. As a result, more than 40,000 Americans lost their lives to opiate overdose in 2016 alone. These data have led to a national movement focused on appropriate opioid prescribing practices. The Centers for Disease Control and Prevention (CDC) developed its Guidelines for Prescribing Opioids for Chronic Pain (2017), a template for pain management and substance assessment in primary care. These CDC guidelines aim to prevent misuse/deaths and early identification of substance use disorders. Although the guidelines are appropriate for initiation of opioid therapy, they are not sufficient to manage patients who have already developed misuse disorders. Other modalities such as medication-assisted treatment (MAT) have been described as beneficial for patients with high risk for or who have an opioid misuse disorder. This article builds on the CDC's 2017 advisory document by applying it in praxis: first, non-opioid medication therapy options and nonmedication therapy options are explored; next, a case study is presented of an integrated primary care-managed patient who presented with both chronic pain and established opioid use disorder. Although the CDC guidelines were not followed in the patient's initial prescription opioid treatment regimen, those guidelines were used as a starting point for follow-up treatment, helping both to assess the patient's risk for opioid misuse disorder and to determine that MAT was an appropriate method of treatment.

Pharmacogenetic Testing in Acute and Chronic Pain: A Preliminary Study

Background and Objectives: Pain is one of the most common symptoms that weighs on life’s quality and health expenditure. In a reality where increasingly personalized therapies are needed, the early use of genetic tests that highlights the individual response to analgesic drugs could be a valuable help in clinical practice. The aim of this preliminary study is to observe if the therapy set to 5 patients suffering of chronic or acute pain is concordant to the Pharmacogenetic test (PGT) results. Materials and Methods: This preliminary study compares the genetic results of pharmacological effectiveness and tolerability analyzed by the genetic test Neurofarmagen Analgesia^®, with the results obtained in clinical practice of 5 patients suffering from acute and chronic pain. Results: Regarding the genetic results of the 5 samples analyzed, 2 reports were found to be completely comparable with the evidences of the clinical practice, while in 3 reports the profile of tolerability and effectiveness were partially discordant. Conclusion: In light of the data not completely overlapping with results observed in clinical practice, further studies would be appropriate in order to acquire more information on the use of Neurofarmagen in routine clinical settings.

Renal impairment and analgesia: From effectiveness to adverse effects

Kidney pain is one of the clinically significant features of renal dysfunction. Mild to severe pain is seen in the lower back area. Painkillers are mostly recommended in these cases to relieve the symptom. Yet, several analgesics are associated with side effects that can worsen the state of the disease. This review is based on the studies conducted in these aspects analgesics used to treat kidney pain and their effectiveness, renal consequences of postoperative analgesia, and pharmacogenetics of these palliatives are briefly summarized in this paper.

An update on the safety of prescribing opioids in pediatrics

INTRODUCTION

The opioid abuse epidemic and its toll on the adolescent population have heightened awareness for safer opioid prescribing practices in pediatric pain management. Opioids remain the mainstay of therapy for severe pain, although there is an emphasis on multimodal therapy. Areas covered: In this update, the authors present information on parenteral/oral opioids commonly used in pediatrics. Recommendations for opioid use in special circumstances including neonates and developmental pharmacokinetic concerns are discussed. Due to noticeable interindividual variability, pharmacogenomics may be important for tailoring pain regimens. In particular, the role of CYP2D6 phenotypes on opioid selection/dosing and clinical implications are discussed. A summary of adverse effects and opioid safety data, and the role of regulations, risk assessment, Centers for Disease Control and Prevention guidelines, follow-up, and monitoring for compliance in opioid prescribing, are detailed. Expert opinion: 'One size does not fit all' describes the need for public policies focused on pediatric pain and opioid use, as children are not 'little adults.' Clinical trials to evaluate pharmacokinetics-pharmacodynamics of opioids are currently lacking. Development of novel biased opioid agonists, clinical integration of genetics in informed decision-making, and emphasis on top-down approaches to pain management will be key to decrease opioid reliance.

Pharmacogenetics in Pain Treatment

Pain is an unpleasant feeling usually resulting from tissue damage that can persist along weeks, months, or even years after the injury, turning into pathological chronic pain, the leading cause of disability. Currently, pharmacology interventions are usually the first-line therapy but there is a highly variable analgesic drug response. Pharmacogenetics (PGx) offers a means to identify genetic biomarkers that can predict individual analgesic response opening doors to precision medicine. PGx analyze the way in which the presence of variations in the DNA sequence (single-nucleotide polymorphisms, SNPs) could be responsible for portions of the population reaching different levels of pain relief (phenotype) due to gene interference in the drug mechanism of action (pharmacodynamics) and/or its concentration at the place of action (pharmacokinetics). SNPs in the cytochrome P450 enzymes genes (CYP2D6) influence metabolism of codeine, tramadol, hydrocodone, oxycodone, and tricyclic antidepressants. Blood concentrations of some NSAIDs depend on CYP2C9 and/or CYP2C8 activity. Additional candidate genes encode for opioid receptors, transporters, and other molecules important for pharmacotherapy in pain management. However, PGx studies are often contradictory, slowing the uptake of this information. This is likely due, in large part, to a lack of robust evidence demonstrating clinical utility and to its polygenic response modulated by other exogenous or epigenetics factors. Novel therapies, including targeting of epigenetic changes and gene therapy-based approaches, broaden future options to improve understanding of pain and the treatment of people who suffer it.

New Advances in Acute Postoperative Pain Management

PURPOSE OF REVIEW

Postoperative pain remains one of the most common challenges following inpatient and outpatient surgeries. With our advances in modern medicine, pain following surgical procedures still remains a challenge, though significant accomplishments have been made over the past few decades. This article highlights some of the promising new advances and approaches in postoperative pain management.

RECENT FINDINGS

Over the last decade, Enhanced Recovery after Surgery (ERAS) pathways and protocols are becoming the benchmark standards for enhancing postoperative recovery. Multimodal analgesia (MMA) is an essential component of such care. Further, in the wake of serious and persistent concern on the opioid epidemic in the USA, there has been a recent renewal of interest in non-opioid alternatives or adjuncts in controlling postoperative pain, often in the context of MMA. Intravenous (IV) acetaminophen, non-steroidal anti-inflammatory drugs (NSAIDs), magnesium, ketamine, dexmedetomidine, liposomal bupivacaine, and newer neuraxial and peripheral regional techniques as well as patient-controlled modalities are gaining importance. Gabapentinoids have become popular but recent meta-analytic reviews have cast doubt on their routine use in perioperative settings. Among opioids, sublingual sufentanil, IV oxycodone, and iontophoretic transdermal fentanyl hold promise. Acupuncture and transcutaneous electrical nerve stimulation may be useful as adjuncts in MMA packages. Genetic testing, derivatives of herbal preparations, and an extended role of acute pain services may emerge as potential areas of importance in the future. There are, however, critical gaps in good quality evidence in many of the practice guideline recommendations. In the era of opioid epidemic, several lines of evidence have emerged to support non-opioid-based drugs and approaches along with a few newer opioid formulations for postoperative pain management, although more research is needed to find the right balance of efficacy and safety.

Comparative pharmacology and toxicology of tramadol and tapentadol

Moderate-to-severe pain represents a heavy burden in patients' quality of life, and ultimately in the society and in healthcare costs. The aim of this review was to summarize data on tramadol and tapentadol adverse effects, toxicity, potential advantages and limitations according to the context of clinical use. We compared data on the pharmacological and toxicological profiles of tramadol and tapentadol, after an extensive literature search in the US National Library of Medicine (PubMed). Tramadol is a prodrug that acts through noradrenaline and serotonin reuptake inhibition, with a weak opioid component added by its metabolite O-desmethyltramadol. Tapentadol does not require metabolic activation and acts mainly through noradrenaline reuptake inhibition and has a strong opioid activity. Such features confer tapentadol potential advantages, namely lower serotonergic, dependence and abuse potential, more linear pharmacokinetics, greater gastrointestinal tolerability and applicability in the treatment of chronic and neuropathic pain. Although more studies are needed to provide clear guidance on the opioid of choice, tapentadol shows some advantages, as it does not require CYP450 system activation and has minimal serotonergic effects. In addition, it leads to less side effects and lower abuse liability. However, in vivo and in vitro studies have shown that tramadol and tapentadol cause similar toxicological damage. In this context, it is important to underline that the choice of opioid should be individually balanced and a tailored decision, based on previous experience and on the patient's profile, type of pain and context of treatment.

SIGNIFICANCE

This review underlines the need for a careful prescription of tramadol and tapentadol. Although both are widely prescribed synthetic opioid analgesics, their toxic effects and potential dependence are not completely understood yet. In particular, concerning tapentadol, further research is needed to better assess its toxic effects.

Integrating pharmacogenetic testing into primary care

Introduction

Pharmacogenetic (PGx) testing has greatly expanded due to enhanced understanding of the role of genes in drug response and advances in DNA-based testing technology development. As many primary care visits result in a prescription, the use of PGx testing may be particularly beneficial in this setting. However, integration of PGx testing may be limited as no uniform approach to delivery of tests has been established and providers are ill-prepared to integrate PGx testing into routine care.

Areas covered

In this paper, the readiness of primary care practitioners are reviewed as well as strategies to address these barriers based on published research and ongoing activities on education and implementation of PGx testing.

Expert Commentary

Widespread integration of PGx testing will warrant continued education and point-of-care decisional support. Primary care providers may also benefit from consultation services or team-based care with laboratory medicine specialists, pharmacists, and genetic counselors.

Pharmacoeconomics of genotyping-based treatment decisions in patients with chronic pain

INTRODUCTION

Genotyping-based treatment decisions may optimize treatment response and minimize adverse drug events (ADEs) in patients with chronic pain.

OBJECTIVES

To estimate the financial impact of genotyping-based treatment decisions in patients with moderate to severe chronic pain in a managed care setting.

METHODS

A budget impact model was built with a 1-year time horizon to estimate costs of genotyping-based treatment decisions in a 1000-patient cohort. The model includes drug costs, type and cost of ADEs, distribution of treatments used, and genotyping costs. Event rates and health care costs were derived from primary literature. Three patient cohorts were assessed with and without genotyping-based treatment decisions: no genetic testing; 50% genetic testing; and 100% genetic testing. Sensitivity analysis was performed varying costs, adherence, and the percentage of patients treated according to genotyping results.

RESULTS

Medical and ADE costs varied by patient severity and genotyping rates. Without genotyping, drug and ADE costs ranged from $1,544,377 to $24,313,844. With genotyping-based treatment, total costs ranged from $1,780,922 to $18,868,032. Sensitivity analysis, varying costs, adherence, and genotyping rates suggested genotyping improves outcomes and is cost saving in patients with chronic pain.

CONCLUSION

Genotyping-based treatment costs are offset by reduced medication utilization and adverse event costs. Genotyping should be considered for patients with chronic pain in clinical practice and within clinical trials.