The 118 A > G polymorphism in the human mu-opioid receptor gene may increase morphine requirements in patients with pain caused by malignant disease

Modulating vertebrate physiology by genomic fine-tuning of GPCR functions

G protein-coupled receptors (GPCRs) play a crucial role as membrane receptors, facilitating the communication of eukaryotic species with their environment and regulating cellular and organ interactions. Consequently, GPCRs hold immense potential in contributing to adaptation to ecological niches and responding to environmental shifts. Comparative analyses of vertebrate genomes reveal patterns of GPCR gene loss, expansion, and signatures of selection. Integrating these genomic data with insights from functional analyses of gene variants enables the interpretation of genotype-phenotype correlations. This review underscores the involvement of GPCRs in adaptive processes, presenting numerous examples of how alterations in GPCR functionality influence vertebrate physiology or, conversely, how environmental changes impact GPCR functions. The findings demonstrate that modifications in GPCR function contribute to adapting to aquatic, arid, and nocturnal habitats, influencing camouflage strategies, and specializing in particular dietary preferences. Furthermore, the adaptability of GPCR functions provides an effective mechanism in facilitating past, recent, or ongoing adaptations in animal domestication and human evolution and should be considered in therapeutic strategies and drug development.

The fine line between relief and risk: new insights into postoperative delirium

There is a complex association between postoperative pain and postoperative delirium, which highlights the need for a more balanced approach to pain management that considers various risk factors. We emphasise the importance of comprehensive documentation and standardised monitoring to improve detection and management of postoperative delirium, ultimately enhancing patient outcomes. We advocate for a precision anaesthesia approach, which tailors care to individual patient profiles, as a potential solution to address these challenges.

Gene polymorphism impact on opioid analgesic usage

Acute pain, moderate-to-severe cancer pain, and persistent malignant pain are all frequently treated with opioids. It is regarded as one of the main tenets of analgesic treatment. The relationship between human opioid sensitivity and genetic polymorphism differences has received little attention up to this point in research. Nonetheless, there is mounting proof that pharmacogenomic diversity could affect how each person reacts to opioids. Finding out how gene polymorphism affects analgesic use is the aim of this investigation, particularly opioids. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses standards were followed in the preparation of the systematic review approach used in this work. Oxycodone, fentanyl, raclopride, tramadol, ketorolac, morphine, ropivacaine, levobupivacaine, subfentanyl, remifentanil, and nortriptyline were the opioid medications used in the study, which was based on 13 publications. From those articles, we reviewed the impact of gene polymorphism on pain management and drug pharmacokinetics. Based on this systematic review, we concluded that gene polymorphism of gene affects analgesic, specifically opioid mechanisms.

OPRM1 rs2075572 has potential to affect plasma buprenorphine level in opioid users, but not OPRM1 rs562859

OPRM1 gene encoding mu-opioid receptor (MOR) is the primary candidate gene for buprenorphine (BUP) pharmacogenetics. OPRM1 undergoes alternative splicing leading to multiple MOR subtypes. Thus, in the current study 2 SNPs (rs1799972 and rs562859) were selected due to evidence for their contribution to alternative splicing of OPRM1. The effects of 2 SNPs of OPRM1 gene on plasma buprenorphine and norbuprenorphine levels in a sample of 233 OUD patients receiving BUP/naloxone were examined. Polymorphisms were analyzed by PCR and RFLP. BUP and norbuprenorphine concentrations in plasma were measured by LC-MS/MS. OPRM1 rs2075572 GC + CC (0.12 ng/ml) had significantly higher plasma BUP level compared to GG (0.084 ng/ml) (p = 0.043). Although there was not a statistically significant difference between OPRM1 rs562859 genotypes (p = 0.46), patients with OPRM1 rs562859 CT + TT had higher plasma BUP and BUP-related values as compared to those with CC. In conclusion, the effect of OPRM1 rs2075572 on BUP levels in opioid users' plasma was shown in a Caucasian population for the first time. On the other hand, OPRM1 rs562859 seems not to influence the BUP pharmacology.

Association of the OPRM1 variant rs1799971 (A118G) and clinical manifestations in tramadol poisoned patients: a cross-sectional study

INTRODUCTION

The opioid receptor mu1 is a protein coding gene that can have different codes for a protein and may have variations (polymorphisms) affecting how opioids work. The aim of this study was to investigate the prevalence of the most common opioid receptor mu1 polymorphism (A118G) and any relationship between this polymorphism and features following tramadol overdose.

MATERIALS AND METHODS

This was a cross-sectional study of patients admitted with tramadol poisoning to an Iranian hospital. These patients were not taking any other drugs or medications and had no history of seizures.

RESULTS

The results showed that among the 83 patients included in the study, 57 (69 per cent) had the AA genotype, 25 (30 per cent) had the AG genotype, and one (1 per cent) had the GG genotype for the opioid receptor mu1 A118G polymorphism. Nausea and/or vomiting occurred in nine (11 per cent) patients and dizziness in 38 (46 per cent) patients. Serious adverse events included seizures in 51 (60 per cent) patients and respiratory failure requiring mechanical ventilation in 21 (25 per cent) patients. However, there was no significant association between the opioid receptor mu1 A118G polymorphism and these adverse events.

DISCUSSION

In our study, the frequency of the A allele was greater than the G allele, and the AA genotype was more prevalent than AG. The GG genotype was the least common among the polymorphisms of opioid receptor mu1 rs1799971. There was no significant association between the opioid receptor mu1 A118G polymorphism and symptoms in tramadol-poisoned patients. Although these allele proportions are similar to the results reported in other Caucasian populations, they are dissimilar to the findings in Chinese and Singaporean populations. In these Asian studies, the predominant allele was the G allele. It has been suggested that a mutated G allele will decrease the production of opioid receptor mu1-related messenger ribonucleic acid and related proteins, leading to fewer mu-opioid receptors in the brain.

CONCLUSIONS

This study found no significant association between the opioid receptor mu1 A118G polymorphism and adverse outcomes in tramadol-poisoned patients. However, more research is needed to draw more definitive conclusions due to the limited evidence and variability of opioid receptor mu1 polymorphisms in different populations.

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.

A systematic review and meta-analysis of the impacts of germline pharmacogenomics on severe toxicity and symptom burden in adult patients with cancer

The clinical application of Pharmacogenomics (PGx) has improved patient safety. However, comprehensive PGx testing has not been widely adopted in clinical practice, and significant opportunities exist to further optimize PGx in cancer care. This systematic review and meta-analysis aim to evaluate the safety outcomes of reported PGx-guided strategies (Analysis 1) and identify well-studied emerging pharmacogenomic variants that predict severe toxicity and symptom burden (Analysis 2) in patients with cancer. We searched MEDLINE, EMBASE, CENTRAL, clinicaltrials.gov, and International Clinical Trials Registry Platform from inception to January 2023 for clinical trials or comparative studies evaluating PGx strategies or unconfirmed pharmacogenomic variants. The primary outcomes were severe adverse events (SAE; ≥ grade 3) or symptom burden with pain and vomiting as defined by trial protocols and assessed by trial investigators. We calculated pooled overall relative risk (RR) and 95% confidence interval (95%CI) using random effects models. PROSPERO, registration number CRD42023421277. Of 6811 records screened, six studies were included for Analysis 1, 55 studies for Analysis 2. Meta-analysis 1 (five trials, 1892 participants) showed a lower absolute incidence of SAEs with PGx-guided strategies compared to usual therapy, 16.1% versus 34.0% (RR = 0.72, 95%CI 0.57-0.91, p = 0.006, I2 = 34%). Meta-analyses 2 identified nine medicine(class)-variant pairs of interest across the TYMS, ABCB1, UGT1A1, HLA-DRB1, and OPRM1 genes. Application of PGx significantly reduced rates of SAEs in patients with cancer. Emergent medicine-variant pairs herald further research into the expansion and optimization of PGx to improve systemic anti-cancer and supportive care medicine safety and efficacy.

The effects of OPRM1 118A>G on methadone response in pain management in advanced cancer at end of life

Cancer pain is the most feared symptom at end of life. Methadone has advantages over other opioids but is associated with significant variability in clinical response, making dosing challenging in practice. OPRM1 is the most studied pharmacogene associated with the pharmacodynamics of opioids, however reports on the association of the A118G polymorphism on opioid dose requirements are conflicting, with no reports including methadone as the primary intervention. This association study on OPRM1 A118G and response to methadone for pain management, includes a review of this genetic factor's role in inter-patient variability. Fifty-four adult patients with advanced cancer were recruited in a prospective, multi-centre, open label dose individualization study. Patient characteristics were not shown to influence methadone response, and no significant associations were observed for methadone dose or pain score. The findings of our review of association studies for OPRM1 A118G in advanced cancer pain demonstrate the importance of taking ancestry into account. While our sample size was small, our results were consistent with European populations, but in contrast to studies in Chinese patients, where carriers of the A118G polymorphism were associated with higher opioid dose requirements. Pharmacogenetic studies in palliative care are challenging, continued contribution will support future genotype-based drug dosing guidelines.

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

Introduction

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

Methods

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

Results

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

Discussion

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

Genome-wide association study on pharmacological outcomes of musculoskeletal pain in UK Biobank

The pharmacological management of musculoskeletal pain starts with NSAIDs, followed by weak or strong opioids until the pain is under control. However, the treatment outcome is usually unsatisfying due to inter-individual differences. To investigate the genetic component of treatment outcome differences, we performed a genome-wide association study (GWAS) in ~23,000 participants with musculoskeletal pain from the UK Biobank. NSAID vs. opioid users were compared as a reflection of the treatment outcome of NSAIDs. We identified one genome-wide significant hit in chromosome 4 (rs549224715, P = 3.88 × 10-8). Suggestive significant (P < 1 × 10-6) loci were functionally annotated to 18 target genes, including four genes linked to neuropathic pain processes or musculoskeletal development. Pathway and network analyses identified immunity-related processes and a (putative) central role of EGFR. However, this study should be viewed as a first step to elucidate the genetic background of musculoskeletal pain treatment.

Genetic Factors Associated with Morphine Consumption in Women Undergoing Laparoscopic Cholecystectomy: A Prospective Cohort Study

Introduction

Morphine has been a crucial analgesic agent used perioperatively in various surgical procedures. Genetic factors can lead to morphine dose requirement interpatient variability. Our objective was to determine the contribution of genetic polymorphisms in human μ-opioid receptor gene (OPRM1), ATP binding cassette gene (ABCB1) and rs2952768 to the variation of the perioperative morphine consumption in women undergoing laparoscopic cholecystectomy.

Methods

This is a prospective cohort study that included 102 adult Arab females undergoing laparoscopic cholecystectomy. The exposures were carrying the genetic variants of OPRM1, ABCB1 and rs2952768. Our primary outcome was total morphine or morphine equivalent dose required perioperatively. The secondary outcomes were pain score during the first 24 hours and adverse drug reactions. A standardized, general anaesthesia was used for all subjects. In addition to the genetic factors, we also investigated non-genetic factors influencing post-operative pain sensitivity and morphine consumption.

Results

Both (rs1799971, A>G) in OPRM1 and (rs2952768, T>C) showed statistically significant association with intra-operative total morphine dose requirements. Patients carrying the "G" allele in OPRM1 had a significantly higher total morphine mean rank dose compared to the AA genotype [62.9 vs 47.1, p=0.008]. Furthermore, patients homozygous for the rs2952768 (T>C) minor allele "CC" had a higher mean rank compared to the other genotypes [72.7 vs 50.1, p=0.046].

Conclusion

OPRM1 (rs1799971) and rs2952768 are associated with variation of intra-operative morphine consumption in laparoscopic cholecystectomy.

Clinical Trial Identifier

This study was registered at ClinicalTrials.gov, NCT04621864. https://clinicaltrials.gov/ct2/show/NCT04621864.

Targeted Therapy for Orofacial Pain: A Novel Perspective for Precision Medicine

Orofacial pain (OFP) is a dental specialty that includes the diagnosis, management and treatment of disorders of the jaw, mouth, face, head and neck. Evidence-based understanding is critical in effectively treating OFPs as the pathophysiology of these conditions is multifactorial. Since OFP impacts the quality of life of the affected individuals, treating patients successfully is of the utmost significance. Despite the therapeutic choices available, treating OFP is still quite challenging, owing to inter-patient variations. The emerging trends in precision medicine could probably lead us to a paradigm shift in effectively managing the untreatable long-standing pain conditions. Precision medicine is designed based on the patient's genetic profile to meet their needs. Several significant relationships have been discovered based on the genetics and genomics of pain in the past, and some of the notable targets are discussed in this review. The scope of this review is to discuss preclinical and clinical trials that include approaches used in targeted therapy for orofacial pain. Future developments in pain medicine should benefit from current trends in research into novel therapeutic approaches.

Association of OPRM1, MIR23B, and MIR107 genetic variability with acute pain, chronic pain and adverse effects after postoperative tramadol and paracetamol treatment in breast cancer

BACKGROUND

Tramadol is an opioid analgesic often used for pain management after breast cancer surgery. Its analgesic activity is due to the activation of the μ-opioid receptor, encoded by the OPRM1 gene. This study investigated the association of genetic variability in OPRM1 and its regulatory miRNA genes with outcomes of tramadol/paracetamol treatment after breast cancer surgery with axillary lymphadenectomy.

PATIENTS AND METHODS

The study included 113 breast cancer patients after breast cancer surgery with axillary lymphadenectomy treated with either 75/650 mg or 37.5/325 mg of tramadol with paracetamol for pain relief within the randomized clinical trial KCT 04/2015-DORETAonko/si at the Institute of Oncology Ljubljana. All patients were genotyped for OPRM1 rs1799971 and rs677830, MIR23B rs1011784, and MIR107 rs2296616 using competitive allele-specific PCR. The association of genetic factors with acute and chronic pain as well as adverse effects of tramadol treatment was evaluated using logistic regression, Fisher's exact test, and Mann-Whitney test.

RESULTS

The investigated OPRM1 related polymorphisms were not associated with acute pain assessed with the VAS scale within four weeks after surgery (all P > 0.05). Carriers of at least one polymorphic OPRM1 rs1799971 allele had a higher risk of constipation in the first four weeks after surgery compared to non-carriers (OR = 4.5, 95% CI = 1.6-12.64, P = 0.004). Carriers of at least one polymorphic OPRM1 rs677830 allele had a higher risk of constipation after third week of tramadol treatment (OR = 3.11, 95% CI = 1.08-8.89, P = 0.035). Furthermore, carriers of two polymorphic MIR23B rs1011784 alleles had a higher risk of nausea after 28 days of tramadol treatment (OR = 7.35, 95% CI = 1.27-42.6, P = 0.026), while heterozygotes for MIR107 rs2296616 allele had a lower risk of nausea after 21 days of tramadol treatment (OR = 0.21, 95% CI = 0.05-0.87, P = 0.031). In carriers of two polymorphic MIR107 rs2296616 alleles, chronic pain was significantly more common than in carriers of two wild-type alleles (P = 0.004). Carriers of at least one polymorphic MIR23B rs1011784 allele experienced more neuropathic pain after adjustment for tramadol dose (OR = 2.85, 95% CI = 1.07-7.59, P = 0.036), while carriers of at least one polymorphic OPRM1 rs677830 allele experienced less neuropathic pain compared to carriers of two wild-type alleles (OR = 0.38, 95% CI = 0.15-0.99, P = 0.047).

CONCLUSIONS

Genetic variability of OPRM1 and genes coding for miRNAs that could affect OPRM1 expression may be associated with adverse effects of tramadol/paracetamol treatment as well as with chronic and neuropathic pain after breast cancer surgery with axillary lymphadenectomy.

Association of genetic variants with patient reported quality of life and pain experience in patients in the UK NCRI Myeloma X Relapse [Intensive]) trial; an exploratory study

The Myeloma X trial provided a platform to explore genetics in relation to systematic assessment of patient-reported outcomes at key points during salvage treatment in multiple myeloma (MM) patients. Blood DNA was obtained in 191 subjects for single nucleotide polymorphism (SNP) genotyping. By univariable analysis, the non-coding rs2562456 SNP, upstream of LINC00664, was associated with several relevant pain and health-related quality-of-life (HRQoL) scores at 100 days after allocation to consolidation with autologous stem cell transplantation or weekly cyclophosphamide. Presence of the minor (C) allele was associated with lower pain interference (p = 0.014) and HRQoL pain (p = 0.003), and higher HRQoL global health status (p = 0.011) and physical functioning (p = 0.007). These effects were not modified by treatment arm and were no longer significant at 6 months. Following induction therapy, the rs13361160 SNP near the CCT5 and FAM173B genes was associated with higher global health (p = 0.027) and physical functioning (p = 0.013). This exploratory study supports associations between subjective parameters in MM with SNPs previously identified in genome-wide association studies of pain. Conversely, SNPs in candidate genes involved in opioid and transporter pathways showed no effect. Further studies are warranted in well-defined cancer populations, and potentially assisted by whole genome sequencing with germline analysis in routine diagnostics in haematological cancers.

Pharmacogenomics of Opioid Treatment for Pain Management

Pain affects approximately 100 million Americans. Pain harms quality of life and costs patients billions of dollars per year. Clinically, nonpharmacologic and pharmacologic therapies can alleviate acute and chronic pain suffering. Opioids are one type of medication used to manage pain. However, opioids can potentially create dependence and substance abuse, and the effects are not consistent in all patients. Pharmacogenomics is the study of the genome to understand the effects of drugs on individual patients based on their genetic information. Through pharmacogenomics, researchers can investigate genetic polymorphisms related to pain that maximize individual patient drug responses and minimize toxicity. This chapter discusses the pharmacogenomics of opioids to treat pain, including individual genetic differences to opioid treatments, opioid pharmacokinetics and pharmacodynamics, and the genetic polymorphisms associated with individual opioid medications.

Novel Probable Glance at Inflammatory Scenario Development in Autistic Pathology

Autism Spectrum Disorder (ASD) is characterized by persistent deficits in social communication and restricted-repetitive patterns of behavior, interests, or activities. ASD is generally associated with chronic inflammatory states, which are linked to immune system dysfunction and/or hyperactivation. The latter might be considered as one of the factors damaging neuronal cells. Several cell types trigger and sustain such neuroinflammation. In this study, we traced different markers of immune system activation on both cellular (immune cell phenotypes) and mediatory levels (production of cytokines) alongside adverse hematology and biochemistry screening in a group of autistic children. In addition, we analyzed the main metabolic pathways potentially involved in ASD development: energy (citric acid cycle components), porphyrin, and neurotransmitter metabolism. Several ASD etiological factors, like heavy metal intoxication, and risk factors-genetic polymorphisms of the relevant neurotransmitters and vitamin D receptors-were also analyzed. Finally, broad linear regression analysis allowed us to elucidate the possible scenario that led to the development of chronic inflammation in ASD patients. Obtained data showed elevated levels of urinary cis-aconitate, isocitrate, alfa-ketoglutarate, and HMG. There were no changes in levels of metabolites of monoamine neurotransmitters, however, the liver-specific tryptophan kinurenine pathway metabolites showed increased levels of quinolinate (QUIN) and picolinate, whereas the level of kynurenate remained unchanged. Abovementioned data demonstrate the infringement in energy metabolism. We found elevated levels of lead in red blood cells, as well as altered porphyrin metabolism, which support the etiological role of heavy metal intoxication in ASD. Lead intoxication, the effect of which is intensified by a mutation of the VDR-Taq and MAO-A, leads to quinolinic acid increase, resulting in energy metabolism depletion and mitochondrial dysfunction. Moreover, our data backing the CD4+CD3+ T-cell dependence of mitochondrial dysfunction development in ASD patients reported in our previous study leads us to the conclusion that redox-immune cross-talk is considered a main functional cell damaging factor in ASD patients.

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.

Genetic Factors Associated With Pain Severity, Daily Opioid Dose Requirement, and Pain Response Among Advanced Cancer Patients Receiving Supportive Care

BACKGROUND

Current understanding of genetic factors associated with pain severity, and improvement of pain with opioids in advanced cancer patients (AC) is inadequate for delivery of personalized pain therapy (PPT). Therefore, the aim of this study was to determine the genetic factors associated with pain severity, daily opioid dose, and pain response in AC patients receiving supportive care.

METHODS

In this prospective study, AC patients were eligible if they had cancer pain ≥4/10 on Edmonton Symptom Assessment Scale (ESAS) - Pain Item and needed opioid rotation for pain control by specialist at the outpatient supportive care center. Association of genetic factors with pain phenotype was assessed using logistic regression models and SKATO (Gene-block) analysis.

RESULTS

About 174/178 (98%) patient samples were analyzed. After adjustment for demographic and clinical variables, pain severity was negatively associated with intron variant alleles in OPRM1 rs9322446, P = 0.02; rs2270459, P = 0.038; rs62052210, P = 0.038. Opioid daily dose was positively associated NFKBIA rs2233419, P = 0.008; rs2233417, P = 0.007; rs3138054, P = 0.008; rs1050851, P = 0.015; ORPM1 rs9479759, P = 0.046; rs2003185, P = 0.047; rs636433, P = 0.044; COMT (rs9306234, P = 0.014; rs165728, P = 0.014; rs2020917, P = 0.036; rs165728, P = 0.034); ARRB2 (rs1045280, P = 0.045); and pain response to opioids was negatively associated OPRM1 rs1319339, P = 0.024; rs34427887, P = 0.048; and COMT rs4646316, P = 0.03; rs35478083, P = 0.028, respectively. SKATO analysis showed association between pain severity and CXCL8 (P = 0.0056), and STAT6 (P = 0.0297) genes respectively, and pain response with IL-6 (P = 0.00499).

CONCLUSIONS

This study identified that SNPs of OPRM1, COMT, NFKBIA, CXCL8, IL-6, STAT6, and ARRB2 genes were associated with pain severity, opioid daily dose, and pain response in AC receiving supportive care. Additional studies are needed to validate our findings for PPT.

Reviewing pharmacogenetics to advance precision medicine for opioids

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Ettienne E. Pharmacogenomics and Morphine

Morphine is an opioid analgesic indicated in the treatment of acute and chronic moderate to severe pain. From a pharmacodynamic standpoint, morphine exerts its effects by agonizing mu-opioid receptors predominantly, resulting in analgesia and sedation. Pharmacokinetically, morphine is primarily metabolized in the liver via glucuronidation by the enzyme uridine diphosphate glucuronosyltransferase family 2 member B7 and encounters the transporter proteins organic cation transporter isoform 1 and P-glycoprotein (adenosine triphosphate-binding cassette subfamily B member 1) as it is being distributed throughout the body. The genes coding for the proteins impacting either the pharmacokinetics or pharmacodynamics of morphine may bear genetic variations, also known as polymorphisms, which may alter the function of the proteins in such a manner that an individual may have disparate treatment outcomes. The purpose of this review is to highlight some of the genes coding for proteins that impact morphine pharmacokinetics and pharmacodynamics and present some treatment considerations.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pain Biomarkers in Cancer: An Overview

BACKGROUND

Pain is a common symptom in oncologic patients and its management is generally guided with reference to pain individually perceived by patients and expressed through self-reported scales. However, the utility of these tools is limited as it strongly depends on patients' opinions. For this reason, more objective instruments are desirable.

OBJECTIVE

In this overview, scientific articles indicating potential markers to be used for pain management in cancer were collected and discussed.

METHODS

Research was performed on principal electronic scientific databases by using the words "pain", "cancer", "markers" and "biomarkers" as the main keywords, and findings describing potential biomarkers for the management of cancer pain were reported.

RESULTS

Studies on pain markers not specific for cancer typology (inflammatory, genetic markers predicting response to analgesic drugs, neuroimaging markers) and pain markers for specific types of cancer (bone cancer, breast cancer, lung cancer, head and neck cancer, prostate cancer, cancer in pediatrics) have been presented and commented on.

CONCLUSION

This overview supports the view of the involvement of inflammatory mediators in the mechanisms underlying cancer pain. Only a small amount of data from research up till today is available on markers that can help in the management of pain, except for pro-inflammatory cytokines and other inflammatory indexes such as C-reactive protein (CRP). However, biomarkers are a promising strategy useful to predict pain intensity and to objectively quantify analgesic response in guiding decisions regarding individual-tailored treatments for cancer patients.

Assessment of safety and effectiveness of oral morphine on patients attending pain and palliative care: a study on Indian population

Opioid analgesics remain the corner stone of effective management of moderate to severe pain. Morphine in its oral and parenteral form is one of the most affordable options left to treat severe cancer pain in most Palliative centres in India. The main objective of our study was to assess the safety and effectiveness, as well as the prescribing pattern of immediate release oral morphine on the Indian population attending Pain and Palliative Care in a multi-speciality hospital. Within the sample population, 74.8% of all patients achieved a pain score reduction of less than or equal to 3 within the 72nd hour. Although the mean baseline pain score was similar in the cancer (8.23±0.75) and the non-cancer (8.26±0.98) group, the mean pain score at the 24th and 72nd hours were significantly different (5.6±1.29 in cancer and 5.09±1.26 in the non-cancer group within the 24th hour, followed by 3.66±1.479 and 3.12±0.88 after the 72nd hour, respectively). The majority of the patients (58.3%) were prescribed at a frequency of 5 mg every 4th hourly, with double dose at bedtime. A similar prescribing trend was seen in both the cancer and non-cancer groups. Moreover, 14 patients underwent dose escalation – with 12 belonging to the cancer group, while 11 patients falling under the cancer group required a switch to different therapy. The major adverse drug reactions (ADR) observed in both study groups were constipation (89.2%), fatigue (37.4%), dry mouth (36%) and nausea/vomiting (23%). The severity of nausea/vomiting and sleepiness was higher in the cancer group whereas itching was more predominant among the non-cancer group.

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.

Mutations in G Protein-Coupled Receptors: Mechanisms, Pathophysiology and Potential Therapeutic Approaches

There are approximately 800 annotated G protein-coupled receptor (GPCR) genes, making these membrane receptors members of the most abundant gene family in the human genome. Besides being involved in manifold physiologic functions and serving as important pharmacotherapeutic targets, mutations in 55 GPCR genes cause about 66 inherited monogenic diseases in humans. Alterations of nine GPCR genes are causatively involved in inherited digenic diseases. In addition to classic gain- and loss-of-function variants, other aspects, such as biased signaling, trans-signaling, ectopic expression, allele variants of GPCRs, pseudogenes, gene fusion, and gene dosage, contribute to the repertoire of GPCR dysfunctions. However, the spectrum of alterations and GPCR involvement is probably much larger because an additional 91 GPCR genes contain homozygous or hemizygous loss-of-function mutations in human individuals with currently unidentified phenotypes. This review highlights the complexity of genomic alteration of GPCR genes as well as their functional consequences and discusses derived therapeutic approaches. SIGNIFICANCE STATEMENT: With the advent of new transgenic and sequencing technologies, the number of monogenic diseases related to G protein-coupled receptor (GPCR) mutants has significantly increased, and our understanding of the functional impact of certain kinds of mutations has substantially improved. Besides the classical gain- and loss-of-function alterations, additional aspects, such as biased signaling, trans-signaling, ectopic expression, allele variants of GPCRs, uniparental disomy, pseudogenes, gene fusion, and gene dosage, need to be elaborated in light of GPCR dysfunctions and possible therapeutic strategies.

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.

OPRM1, OPRK1, and COMT genetic polymorphisms associated with opioid effects on experimental pain: a randomized, double-blind, placebo-controlled study

Genetic polymorphisms have been shown to affect opioid requirement for pain relief. However, true genetic effect is often difficult to assess due to underlying pain conditions and placebo effects. The goal of this study was to understand how common polymorphisms affect opioid effects while controlling for these factors. A randomized, double-blind, placebo-controlled study was implemented to assess how opioid effects are modulated by COMT (rs6269, rs4633, rs4848, rs4680), OPRM1 (A118G), and OPRK1 (rs1051660, rs702764, rs16918875). One hundred and eight healthy subjects underwent experimental pain testing before and after morphine, butorphanol, and placebo (saline). Association analysis was performed between polymorphisms/haplotypes and opioid response, while correcting for race, gender, placebo effects, and multiple comparisons. Pressure pain was significantly associated with rs6269 and rs4633 following butorphanol. The AA genotype of rs4680 or A_T_C_A/ A_T_C_A (rs6269_rs4633_ rs4818_rs4680) diplotype of COMT, combined with the AG genotype of OPRM1 A118G, showed significantly increased pressure pain threshold from butorphanol. Opioid effects on pressure, ischemic, heat pain, and side effects were nominally associated with several SNPs and haplotypes. Effects were often present in one opioid but not the other. This indicates that these polymorphisms affect pain relief from opioids, and that their effects are opioid and pain modality specific.

Post-translational Modifications of Opioid Receptors

Post-translational modifications (PTMs) are key events in signal transduction since they affect protein function by regulating their abundance and/or activity. PTMs involve the covalent attachment of functional groups to specific amino acids. Since they tend to be generally reversible, PTMs serve as regulators of signal transduction pathways. G-protein-coupled receptors (GPCRs) are major signaling proteins that undergo multiple types of PTMs. In this Review, we focus on the opioid receptors, members of GPCR family A, and highlight recent advances in the field that have underscored the importance of PTMs in the functional regulation of these receptors. Since opioid receptor activity plays a central role in the development of tolerance and addiction to morphine and other drugs of abuse, understanding the molecular mechanisms regulating receptor activity is of fundamental importance.

Pain Management Using Clinical Pharmacy Assessments With and Without Pharmacogenomics in an Oncology Palliative Medicine Clinic

PURPOSE:

Approximately 30% of patients with cancer who have pain have symptomatic improvement within 1 month using conventional pain management strategies. Engaging clinical pharmacists in palliative medicine (PM) and use of pharmacogenomic testing may improve cancer pain management.

METHODS:

Adult patients with cancer with uncontrolled pain had baseline assessments performed by PM providers using the Edmonton Symptom Assessment Scale. Pharmacotherapy was initiated or modified accordingly. A subset of patients consented to pharmacogenomic testing. The first pharmacy assessment occurred within 1 week of baseline and a second assessment was done within another week if intervention was required. Each patient’s final visit was at 1 month. Pain improvement rate (a reduction of two or more points on a 0-to-10 pain scale) from baseline to final visit was compared applying the Fisher exact test to published historical control data, and between patients with and without pharmacogenomic testing. Multivariate logistic regression identified pain improvement covariates.

RESULTS:

Of 142 patients undergoing pharmacy assessments, 53% had pain improvement compared with 30% in historical control subjects ( P < .001). Pain improvement was not different between those who received (n = 43) and did not receive (n = 99) pharmacogenomics testing (56% v 52%; P = .716). However, of 15 patients with an actionable genotype, 73% had pain improvement. Higher baseline pain (odds ratio [OR], 1.79; 95% CI, 1.43 to 2.24; P < .001), black or other race (OR, 0.42; 95% CI, 0.18 to 0.95; P = .04), and performance status 3 or 4 (OR, 0.18; 95% CI, 0.04 to 0.83; P = .03) were associated with odds of pain improvement, but pharmacogenomic testing was not ( P = .64).

CONCLUSION:

Including pharmacists in PM improves pain management effectiveness. Although pharmacogenomics did not statistically improve pain, a subset of patients with actionable genotypes may have benefited, warranting larger and randomized studies.

The association between the OPRM1 A118G polymorphism and addiction in a Turkish population

Susceptibility to addiction has a complex genetic basis that includes genes associated with the action and metabolism of drugs of abuse. One important gene in that respect is OPRM1, which codes for the μ-opioid receptor and has an important role in mediating the rewarding effects of addiction substances. The aim of our study was to assess the prevalence of the OPRM1 A118G polymorphism (rs1799971) in Turkish population and to investigate its association with opioid and other substance addiction. In addition, we examined the association of rs1799971 in addicted patients who were also diagnosed with psychiatric disorders. The study included 103 patients addicted to opioids, cocaine, ecstasy, alcohol, lysergic acid diethylamide (LSD), cannabis, and sedative/hypnotic substances and 83 healthy volunteers with similar demographic features as controls. rs1799971 polymorphisms were identified with the polymerase chain reaction restriction fragment length polymorphism method (PCR-RFLP). The genotype frequencies were significantly higher in the addicted patients than controls (32.0 % vs 16.9 %, respectively; p=0.027). The prevalence of the G allele was 16.1 % in the addicted group and 8.4 % in the control group (p=0.031). Our study confirmed the association between the rs1799971(G) allele frequency and opioid and other substance addiction, but not with psychiatric disorders.

OPRM1 A118G Polymorphisms and Its Role in Opioid Addiction: Implication on Severity and Treatment Approaches

The epidemic of opioid addiction is shaping up as the most serious clinical issues of current times. Opioids have the greatest propensity to develop addiction after first exposure. Molecular, genetic variations, epigenetic alterations, and environmental factors are also implicated in the development of opioid addiction. Genetic and epigenetic variations in candidate genes have been identified for their associations with opioid addiction. OPRM1 nonsynonymous single nucleotide polymorphism rs1799971 (A118G) is the most prominent candidate due to its significant association with onset and treatment of opioid addiction. Marked inter-individual variability in response to available maintenance pharmacotherapies is the common feature observed in individuals with opioid addiction. Several therapies are only effective among subgroups of opioid individuals which indicate that ethnic, environmental factors and genetic polymorphism including rs1799971 may be responsible for the response to treatment. Pharmacogenetics has the potential to enhance our understanding around the underlying genetic, epigenetic and molecular mechanisms responsible for the heterogeneous response of maintenance pharmacotherapies in opioid addiction. A more detailed understanding of molecular, epigenetic and genetic variants especially the implication of OPRM1 A118G polymorphism in an individual may serve as the way forward to address the opioid epidemic. Personalized medicine, which involves developing targeted pharmacotherapies in accordance with individual genetic and epigenetic makeup, are required to develop safe and effective treatments for opioid addiction.

Association between vitamin D receptor gene FokI and TaqI variants with autism spectrum disorder predisposition in Iranian population

BACKGROUND AND AIM

Autism spectrum disorder (ASD) is one of the neurodevelopmental and cognitive conditions that involves 1 in 160 children around the world. Several studies showed that there is a relationship between vitamin D receptor (VDR) gene polymorphisms with the neurodevelopmental behavioral disorders. In the current study, we aimed to highlight the association of VDR gene polymorphisms (FokI and TaqI) with the risk of autism in Birjand population.

MATERIAL AND METHODS

In this case-control study eighty-one patients recognized with ASD and one hundred-eight healthy controls were recruited to the study from 2017 to 2018. Genotyping was carried out by polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) technique for all subjects.

RESULTS

Calculated odds ratio and P-value for the alleles of VDR gene FokI and TaqI variants between autistic patients and controls did not show a significant difference (P > 0.05). However, calculated homozygous recessive (tt) for TaqI polymorphism was statistically significant (P = 0.015) in control group and there was also statistically meaningful difference in both case and control groups in ft haplotype (P = 0.04).

CONCLUSION

These results provide preliminary evidence that genetic variants of the VDR gene (FokI and TaqI) might have a possible reduced risk of ASD occurrence in children. The additional examination is needed to acquire more decisive and precise results in this area.

Genetic Contribution in Low Back Pain: A Prospective Genetic Association Study

OBJECTIVES

Chronic pain is one of the most common reasons individuals seek medical attention. It is a major issue because of the wide interindividual variability in the analgesic response. This might be partly explained by the presence of variants in genes encoding molecules involved in pharmacodynamics and pharmacokinetics. The aim was to analyze opioid effectiveness in chronic low back pain (CLBP) relief after opioid titration, unveiling the impact of pharmacogenetics.

METHODS

The study included 231 opioid-naïve patients from the Spine Unit; age 63 ± 14 years, 64% female, body mass index 29 ± 6 kg/m² , visual analog scale pain intensity score 73 ± 16 mm. Clinical data were collected at baseline, 3 months after opioid titration, and after 2 to 4 years of follow-up concerning pain (intensity and relief), quality of life, disability, comorbidities, and drug prescription (opioid dose, rotations, and adverse events). The genotype influence of OPRM1, COMT, UGT2B7, ABCB1, KCNJ6, and CYP3A5*3A in analgesic response was analyzed by reverse-transcription polymerase chain reaction genotyping.

RESULTS

Patients with the COMT G472A-AA genotype (rs4680) and KCNJ6 A1032G-A allele (rs2070995) CLBP responded differently to opioid titration, with higher pain intensity requiring higher dosing. Furthermore, GG- genotypes of A118G (OPRM1, rs1799971) and A854G (UGT2B7, rs776746) influenced the neuropathic component. After opioid titration, CLBP intensity, neuropathic component, low back pain disability, anxiety, and depression significantly decreased, while quality of life improved.

CONCLUSION

Single-nucleotide polymorphisms in genes involved in pain transmission and opioid metabolism might predispose to exaggerated sensitivity and differences in the opioid analgesic effect in patients with CLBP. We encourage clinical trials for their clinical application in chronic pain management.

Increased risk of intracranial hemorrhage in preterm infants with OPRM1 gene A118G polymorphism

Background

To investigate the relationship between the OPRM1 gene A118G polymorphism and intracranial hemorrhage (ICH) in premature infants and identify the relevant genes in disease occurrence.

Methods

In the present case study analysis, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to detect the genotype and allele frequencies of the OPRM1 gene All8G single nucleotide polymorphism (SNP) in a case group of premature infants with ICH (n=167) and a control group of premature infants (n=163) without ICH.

Results

In the case group, 73 (43.7%) wild type A118 homozygous (A/A), 82 (49.1%) mutant heterozygous (A/G), and 12 (7.2%) mutant G118 homozygous (G/G) individuals were observed. The frequencies of A and G alleles were 68.3% and 31.7% respectively. In the control group, 89 (54.6%) wild type A118 homozygous (A/A), 68 (41.7%) mutant heterozygous (A/G), and 6 (3.7%) mutant G118 homozygous (G/G) individuals were observed. The frequencies of A and G alleles were 75.5% and 24.5% respectively. There was no significant difference in the frequency distribution of the OPRM1 gene A118G polymorphism between the two groups (χ²=4.839, P=0.089). There was a significant difference in the positive rate of wild-type AA and mutant-type (A/G + G/G) between the two groups (χ²=3.913, P=0.048). Carrying the G allele of the individual was 1.5 times more frequent suffering from the risk of ICH than carrying the A allele [odds ratio (OR): 1.549; 95% confidence interval (CI): 1.003-2.391], indicating that the OPRM1 118G allele was positively correlated with ICH and can increase the risk of ICH occurrence.

Conclusions

The OPRM1 gene A118G polymorphism is associated with ICH in premature infants. The OPRM1 gene A118G may play a critical role in the occurrence of ICH.

Update on the pharmacogenomics of pain management

Pharmacogenomics is the study of genetic variants that impact drug effects through changes in a drug’s pharmacokinetics and pharmacodynamics. Pharmacogenomics is being integrated into clinical pain management practice because variants in individual genes can be predictive of how a patient may respond to a drug treatment. Pain is subjective and is considered challenging to treat. Furthermore, pain patients do not respond to treatments in the same way, which makes it hard to issue a consistent treatment regimen for all pain conditions. Pharmacogenomics would bring consistency to the subjective nature of pain and could revolutionize the field of pain management by providing personalized medical care tailored to each patient based on their gene variants. Additionally, pharmacogenomics offers a solution to the opioid crisis by identifying potentially opioid-vulnerable patients who could be recommended a nonopioid treatment for their pain condition. The integration of pharmacogenomics into clinical practice creates better and safer healthcare practices for patients. In this article, we provide a comprehensive history of pharmacogenomics and pain management, and focus on up to date information on the pharmacogenomics of pain management, describing genes involved in pain, genes that may reduce or guard against pain and discuss specific pain management drugs and their genetic correlations.

The pharmacogenetics of natural products: A pharmacokinetic and pharmacodynamic perspective

Natural products have represented attractive alternatives for disease prevention and treatment over the course of human history and have contributed to the development of modern drugs. These natural products possess beneficial efficacies as well as adverse efffects, which vary largely among individuals because of genetic variations in their pharmacokinetics and pharmacodynamics. As with other synthetic chemical drugs, the dosing of natural products can be optimized to improve efficacy and reduce toxicity according to the pharmacogenetic properties. With the emergence and development of pharmacogenomics, it is possible to discover and identify the targets/mechanisms of pharmacological effects and therapeutic responses of natural products effectively and efficiently on the whole genome level. This review covers the effects of genetic variations in drug metabolizing enzymes, drug transporters, and direct and indirect interactions with the pharmacological targets/pathways on the individual response to natural products, and provides suggestions on dosing regimen adjustments of natural products based on their pharmacokinetic and pharmacogenetic paratmeters. Finally, we provide our viewpoints on the importance and necessity of pharmacogenetic and pharmacogenomic research of natural products in natural medicine's rational development and clinical application of precision medicine.

Genetic Variants Associated with Cancer Pain and Response to Opioid Analgesics: Implications for Precision Pain Management

OBJECTIVE

To review the current knowledge on the association of genetic variants with cancer pain.

DATA SOURCES

Data-based publications and review articles retrieved from PubMed, CINAHL, and Web of Science, as well as an additional search in Google Scholar.

CONCLUSION

Genetic variability can influence differential pain perception and response to opioids in cancer patients, which will have implications in the optimal personalized treatment of cancer pain. More studies are warranted to replicate findings.

IMPLICATIONS FOR NURSING PRACTICE

Nurses are poised to educate patients on biomarker testing and interpretation and to use precision pain management strategies based on this information.

Potential biomarkers for persistent and neuropathic pain therapy

Persistent, in particular neuropathic pain affects millions of people worldwide. However, the response rate of patients to existing analgesic drugs is less than 50%. There are several possibilities to increase this response rate, such as optimization of the pharmacokinetic and pharmacodynamic properties of analgesics. Another promising approach is to use prognostic biomarkers in patients to determine the optimal pharmacological therapy for each individual. Here, we discuss recent efforts to identify plasma and CSF biomarkers, as well as genetic biomarkers and sensory testing, and how these readouts could be exploited for the prediction of a suitable pharmacological treatment. Collectively, the information on single biomarkers may be stored in knowledge bases and processed by machine-learning and related artificial intelligence techniques, resulting in the optimal pharmacological treatment for individual pain patients. We highlight the potential for biomarker-based individualized pain therapies and discuss biomarker reliability and their utility in clinical practice, as well as limitations of this approach.

Pain polymorphisms and opioids: An evidence based review

Despite the various different candidate genetic polymorphisms of potential clinical relevance, there is not enough understanding of the inter-individual variability in analgesic administration. The cytochrome P450 2D6 (CYP2D6) genotype is thought to be one of the most studied. The aim of the present evidence-based review was to determine if there is now sufficient evidence to make clinical recommendations based on a specific genomic profile. The data sources utilized were as follows: PubMed (NLM) database, Evidence Based Medicine Guidelines and Google. Research on clinical guidance standards, systematic reviews, meta-analyses and clinical trials, published prior to January 2018, were evaluated in English, using the MeSH terms ‘cancer pain’, ‘polymorphism’, ‘genetic’ and ‘gene polymorphism’. To assess the level of evidence, the Strength of Recommendation Taxonomy of the American Family Physician was applied. From the initial search, 12 systematic reviews and/or meta-analyses, 5 clinical trials and 10 guidelines were selected. The results indicated that genetic variation of µ-opioid receptor 1 (OPRM1) may contribute to inter-individual differences in morphine consumption with recommendation grade A for OPRM A118G single nucleotide polymorphism (rs1799971). Polymorphisms associated with the metabolization process of morphine and other opioid drugs are very relevant in opioid titration and ethnic subgroup differences which have to be taken into account (particularly, for the recommendation grade A for the CYP2D6 polymorphism). In human studies, the catechol-O-methyl transferase (COMT) genotype affects the efficacy of opioids in acute and chronic pain under different settings, with recommendation grade B to the COMT single nucleotide polymorphism rs4680 (Val/Met). Finally, polymorphisms of the ATP-binding cassette family of efflux transporters were highlighted. Consistent data on pain polymorphisms is now widely available; however, these results have had very little impact on clinical guidelines and daily oncologist practice. Persisting pain, side effects of grade 3 (NCI-CTCAE v4.0) and breakthrough pain with more than 4 episodes/day should be considered the criteria for pain multidisciplinary team discussions and for polymorphism screening.

Development of an AmpliSeqTM Panel for Next-Generation Sequencing of a Set of Genetic Predictors of Persisting Pain

Background: Many gene variants modulate the individual perception of pain and possibly also its persistence. The limited selection of single functional variants is increasingly being replaced by analyses of the full coding and regulatory sequences of pain-relevant genes accessible by means of next generation sequencing (NGS).

Methods: An NGS panel was created for a set of 77 human genes selected following different lines of evidence supporting their role in persisting pain. To address the role of these candidate genes, we established a sequencing assay based on a custom AmpliSeq^TM panel to assess the exomic sequences in 72 subjects of Caucasian ethnicity. To identify the systems biology of the genes, the biological functions associated with these genes were assessed by means of a computational over-representation analysis.

Results: Sequencing generated a median of 2.85 ⋅ 10⁶ reads per run with a mean depth close to 200 reads, mean read length of 205 called bases and an average chip loading of 71%. A total of 3,185 genetic variants were called. A computational functional genomics analysis indicated that the proposed NGS gene panel covers biological processes identified previously as characterizing the functional genomics of persisting pain.

Conclusion: Results of the NGS assay suggested that the produced nucleotide sequences are comparable to those earned with the classical Sanger sequencing technique. The assay is applicable for small to large-scale experimental setups to target the accessing of information about any nucleotide within the addressed genes in a study cohort.

Gamma-aminobutyric acid transaminase genetic polymorphism is a candidate locus for responsiveness to opioid analgesics in patients with cancer pain: An exploratory study

Aim

Cancer pain impairs not only physical functions but also social functions and roles. Consequently, the overall health‐related quality of life of patients with cancer pain deteriorates. Opioid analgesics are recommended for treating moderate to strong cancer pain. Advances in human genome research have fueled a growing interest to understand individual differences in responsiveness to opioid analgesics. This study aimed to explore and identify novel loci for genes predisposing an individual to opioid analgesic responsiveness.

Methods

A total of 71 cancer patients rated their pain on an 11‐point numerical rating scale twice before and after increasing opioid analgesics. A genomewide association study focusing on single nucleotide polymorphisms (SNPs) was conducted to associate pain decrease with increased dosage of opioid analgesics based on weight (ie, responsiveness to opioid analgesics). A genomewide significance (P < 5E‐8) was set for multiplicity of analyses to control for false positives.

Results

Two SNPs passed the genomewide threshold for significance. One exonic SNP (rs1641025) was located in the ABAT [4‐aminobutyrate aminotransaminase (GABA transaminase)] gene on chromosome 16. The other SNP (rs12494691) was located on chromosome 3, which was not associated with any known genes. These SNPs were not associated with opioid‐related adverse effects.

Conclusions

Our results preliminarily suggest that both SNPs might be potential candidate loci for responsiveness to opioid analgesics, and GABA transaminase might be a possible target for developing adjuvant pharmacotherapy with opioid analgesics in adjuvant pharmacotherapy. Our results should be validated in a large‐scale study with a larger sample size.

A genome‐wide association study revealed two candidate single nucleotide polymorphisms for responsiveness to opioid analgesics in patients with cancer pain, one of which locates on the GABA transaminase gene.

Value of Supportive Care Pharmacogenomics in Oncology Practice

Genomic medicine provides opportunities to personalize cancer therapy for an individual patient. Although novel targeted therapies prolong survival, most patients with cancer continue to suffer from burdensome symptoms including pain, depression, neuropathy, nausea and vomiting, and infections, which significantly impair quality of life. Suboptimal management of these symptoms can negatively affect response to cancer treatment and overall prognosis. The effect of genetic variation on drug response-otherwise known as pharmacogenomics-is well documented and directly influences an individual patient's response to antiemetics, opioids, neuromodulators, antidepressants, antifungals, and more. The growing body of pharmacogenomic data can now guide clinicians to select the safest and most effective supportive medications for an individual patient with cancer from the very first prescription. This review outlines a theoretical patient case and the implications of using pharmacogenetic test results to personalize supportive care throughout the cancer care continuum.

IMPLICATIONS FOR PRACTICE

Integration of palliative medicine into the cancer care continuum has resulted in increased quality of life and survival for patients with many cancer types. However, suboptimal management of symptoms such as pain, neuropathy, depression, and nausea and vomiting continues to place a heavy burden on patients with cancer. As demonstrated in this theoretical case, pharmacogenomics can have a major effect on clinical response to medications used to treat these conditions. Recognizing the value of supportive care pharmacogenomics in oncology and application into routine practice offers an objective choice for the safest and most effective treatment compared with the traditional trial and error method.

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

Objective

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

Method

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

Results

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

Conclusions

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

OPRM1 influence on and effectiveness of an individualized treatment plan for prescription opioid use disorder patients

Screening for opioid use disorder should be considered in chronic non-cancer pain (CNCP) patients with long-term use of opioids. The aim of our study was to assess the effectiveness of an individualized treatment plan (ITP) for prescription opioid dependence that included screening of pharmacogenetic markers. An observational prospective study was performed using prescription opioid-dependent CNCP outpatients (n = 88). Patients were divided into nonresponders, responders, or high responders according to their response to the ITP. Genotyping of OPRM1 (A118G), OPRD1 (T921C), COMT (G472A), ABCB1 (C3435T), and ARRB2 (C8622T) was performed by real-time PCR. Our ITP achieved a significant reduction of the morphine equivalent daily dose (MEDD) in 64% of responders, including 33% of high responders. Nonopioid medication or buprenorphine use was significantly higher at final versus basal visit. 118-AA OPRM1 patients required significantly lower MEDD at basal and final visits. Our ITP showed effectiveness and security in reducing MEDD in opioid-dependent patients, with good conversion to buprenorphine that was more pronounced in 118-AA OPRM1 patients.