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7 recordsLinked to original sources
PubMed2026

Role of OPRM1 A118G polymorphism in tramadol analgesia following third molar surgery: a pharmacogenomic study.

BACKGROUND: The OPRM1 A118G (rs1799971) polymorphism has been implicated in interindividual variability in opioid analgesic response, but its influence on tramadol efficacy remains uncertain. This study evaluated the association between OPRM1 A118G and postoperative analgesic response to tramadol following mandibular third molar surgery. METHODS: In this prospective pharmacogenomic study, 53 adults undergoing impacted mandibular third molar extraction were enrolled. Genomic DNA was analyzed for OPRM1 A118G (rs1799971) using amplification refractory mutation system polymerase chain reaction (ARMS-PCR). All procedures were performed under 2% lignocaine with adrenaline. Tramadol (50 mg) was administered after the onset of postoperative pain. Pain intensity was assessed using the Visual Analogue Scale (VAS) and Short-Form McGill Pain Questionnaire at 2, 4, and 6 hours. The primary outcome was summed pain intensity difference (SPID, 2-6 hours). RESULTS: Genotype frequencies were in Hardy-Weinberg equilibrium. No significant association was observed between OPRM1 genotype and SPID, VAS reduction, Pain Rating Index change, or responder status during the 6-hour observation period (all p > 0.05). CONCLUSION: OPRM1 A118G was not significantly associated with early tramadol analgesic response following third molar surgery. Larger studies incorporating both OPRM1 and CYP2D6 genotyping are needed to clarify the genetic determinants of tramadol analgesia as CYP2D6 gene is required for tramadol metabolism.

OPRM1↗
PubMed2026

Differential impacts of exon 1-associated and exon 11-associated variants of the rat mu opioid receptor gene, Oprm1, on buprenorphine- and morphine-induced analgesia and respiratory depression in male rats.

Buprenorphine has long been recognized as a mu opioid agonist with a distinctive and intricate pharmacological profile. It is a partial agonist at the mu opioid receptor, an antagonist at the kappa and delta opioid receptors, and an agonist at the nociception opioid receptor. Similar to other mu agonists such as morphine and fentanyl, buprenorphine can produce side effects, including tolerance, physical dependence, respiratory depression, and addiction. The mu opioid receptor gene, OPRM1, undergoes extensive alternative splicing, generating an array of splice variants or isoforms, which are conserved from rodents to humans. These splice variants can be categorized into 2 main types, exon 1 (E1)-associated variants and exon 11 (E11)-associated variants. E1-associated variants primarily consist of full-length, 7-transmembrane C-terminal variants, whereas E11-associated variants are typically truncated 6-transmembrane variants. Previous studies established that buprenorphine analgesia in mice is dependent on both E1- and E11-associated variants. However, the role of these variants in buprenorphine analgesia and respiratory depression in rats remains unclear. In this study, we used CRISPR/Cas9 technology to develop 2 rat Oprm1 gene-targeting models in which E1- and E11-associated variants were selectively disrupted, aiming to investigate their roles in buprenorphine and morphine's actions. The results showed that both E1- and E11-associated variants are essential for buprenorphine's analgesic and respiratory depressional effects in rats, whereas morphine's effects are solely attributed to the E1-associated variants. These findings provide new and important insights into the distinct contributions of the E1- and E11-associated variants to the pharmacological actions of buprenorphine and morphine. SIGNIFICANCE STATEMENT: Differential dependences of buprenorphine and morphine analgesia and respiratory depression on Oprm1 exon 1- and exon 11-associated variants revealed in rat gene-targeting models provide new and important insights into unique contributions of these variants to buprenorphine and morphine actions.

Animals↗
PubMed2024

Associations between (pharmaco-)genetic markers and postoperative pain after inguinal hernia repair - a prospective study protocol.

BACKGROUND: Postoperative pain is a common complication following surgery, with severity and duration varying between patients. Chronic postoperative pain after inguinal hernia surgery has an incidence rate of approximately 10%. Risk factors for acute and chronic pain following hernia surgery include age, sex, psychosocial factors, and demographic background. Additionally, genetic polymorphisms in enzymes involved in pain mechanisms, as well as the metabolism of analgesics might influence pain perception, pain development, and response to pain medications. Key enzymes include the catechol-o-methyltransferase (COMT), the µ-opioid receptor 1 (OPRM1), and the cytochrome P450 2D6 (CYP2D6). CYP2D6 plays a crucial role in metabolizing analgesics such as tramadol, codeine, and oxycodone. It is also suspected to be involved in the synthesis of catecholamines and endogenous morphines suggesting a potential role in pathophysiology of pain. We hypothesize that the CYP2D6 activity influences the development of postoperative pain after hernia surgery. METHODS: This study is a prospective, observational, multicenter association study investigating adult patients scheduled for inguinal hernia surgery using a robotic-assisted (rTAPP) approach. Patients are enrolled during the preoperative surgical consultation. A buccal swab is collected for genetic testing at this time. Pain at the site of the hernia is assessed using the validated EuraHSQoL score preoperatively and at 2, 4, and 6 weeks postoperatively. Additionally, information on co-medication and details of the surgery will be collected. The planned number of participants is 350 patients. The primary objective is to analyze the association between different genotype-predicted CYP2D6 phenotypes and patient-reported pain intensity 6 weeks after surgery. Secondary objectives include the association between further genetic variants, such as the COMT rs4680 and OPRM1 rs1799971 genotype, and pain severity. Additionally, the potential of pharmacogenetic panel testing to optimize analgesic therapy in hernia surgery patients will be explored. DISCUSSION: The findings of this study are expected to provide valuable insights into identifying patients at higher risk for postoperative pain before surgery. This knowledge could pave the way for tailored interventions during and after surgery for these specific patients. TRIAL REGISTRATION: Deutsches Register Klinischer Studien https://www.drks.de/DRKS00034796 Registered on August 07, 2024.

Genetic Association Studies↗
PubMed2025

Genetic and Epigenetic Approaches to Opioid Use Disorder.

BACKGROUND: Opioid use disorder (OUD) is a major global-scale social issue affecting public health. The high potential for addiction and dependence makes opioid use a significant concern, contributing to substance-related disorders. Both genetic and environmental factors contribute to the predisposition to OUD, with the opioidergic, dopaminergic, and GABAergic systems playing primary roles in itsonset. METHODS: This narrative review documents the association between genes and their variants related to these three systems, along with current evidence on epigenetic interventions in OUD. Relevant studies investigating candidate-gene associations and molecular mechanisms were synthesized to highlight genetic variants and epigenetic processes linked to OUD. RESULTS: Genetic associations play a prominent role in OUD, with several single-nucleotide variants identified in affected populations. Key genes implicated include OPRM1, OPRD1, OPRK1, PDYN, OPRL1, and POMC from the opioidergic system; DRD1, DRD2, DRD3, DRD4, ANKK1, and COMT from the dopaminergic system; and GABRA2, GABRB3, GABRG2, GAD1, and GAD2 from the GABAergic system. Evidence also indicates that chronic opioid use is associated with epigenetic changes through posttranslational histone modifications and DNA methylation. However, limitations in existing studies include small sample sizes, limited replication, and potential stratification biases. CONCLUSIONS: Although many candidate-gene associations have been proposed for OUD, robust evidence remains limited. Large, ancestrally diverse genome-wide association studies (GWAS) and systematic replication studies are urgently needed. A deeper understanding of the genetic, epigenetic, and neurobiological bases of addiction will be essential for the development of precisely targeted medications to improve prevention and treatment outcomes for OUD.

Humans↗
PubMed2022

Cross-ancestry meta-analysis of opioid use disorder uncovers novel loci with predominant effects in brain regions associated with addiction.

Despite an estimated heritability of ~50%, genome-wide association studies of opioid use disorder (OUD) have revealed few genome-wide significant loci. We conducted a cross-ancestry meta-analysis of OUD in the Million Veteran Program (N = 425,944). In addition to known exonic variants in OPRM1 and FURIN, we identified intronic variants in RABEPK, FBXW4, NCAM1 and KCNN1. A meta-analysis including other datasets identified a locus in TSNARE1. In total, we identified 14 loci for OUD, 12 of which are novel. Significant genetic correlations were identified for 127 traits, including psychiatric disorders and other substance use-related traits. The only significantly enriched cell-type group was CNS, with gene expression enrichment in brain regions previously associated with substance use disorders. These findings increase our understanding of the biological basis of OUD and provide further evidence that it is a brain disease, which may help to reduce stigma and inform efforts to address the opioid epidemic.

Behavior, Addictive↗
PubMed2026

Optimizing Control Definitions in Opioid Use Disorder Genetic Research Using Electronic Health Records.

Amidst the opioid crisis, understanding the genetic basis of opioid use disorder (OUD) is crucial for identifying biological mechanisms and intervention points. However, genome-wide association studies (GWASs) have been hampered by inadequate sample sizes and often the use of control populations not assessed for prior opioid exposure. Because opioid exposure is a prerequisite for the development of OUD, consideration of exposure history in controls is important. Electronic health record data (EHR) paired with genomic information allow a broader sampling of patients with OUD and exposed controls. We leveraged data across two healthcare systems to evaluate the impact of using controls not screened for opioid exposure ('generic') versus minimally opioid-exposed control ('exposed'). First, at the phenotypic level, we conducted phenome-wide association studies (PheWAS) to compare the medical comorbidity profiles of OUD cases when using generic versus exposed controls. While PheWAS results for OUD-related comorbidities were more pronounced when using the generic group, 83% of the disease associations were overlapping and of similar effect sizes. Second, at the genetic level, we conducted GWAS (cases vs. generic; cases vs. exposed) and assessed differences in genetic correlations and degrees of phenotypic misclassification. Genetic results were concordant across control groups based on heritability (generic: 0.16 ± 0.07 vs. 0.10 ± 0.07), associations with the coding OPRM1 variant rs1799971 (pgeneric = 8.83E-03 vs. pexposed = 1.83E-02) and genetic correlations with prior OUD GWAS (rg-generic = 0.83 ± 0.26 vs. rg-exposed = 0.78 ± 0.27). Although GWASs were limited by sample size (Ngeneric = 6269, Nexposed = 6365), compared to an independent OUD GWAS (N = 425 944), the dilution value for the two GWAS was not different from 1, suggesting no major impact of phenotypic misclassification. This study represents the first effort to enhance OUD genetic research through optimization of control definitions using EHR data. Generic controls ascertained within the US health systems, where exposure to prescription opioids is high, offer a practical alternative for genetic studies of OUD.

Humans↗
PubMed2026

Unraveling the Mystery of Pain: A Unique Clinical Encounter and Case Report.

BACKGROUND: The Clinical Pharmacogenetics Implementation Consortium published an updated guideline for opioids and CYP2D6, OPRM1, and COMT in December 2020. These guidelines include recommendations to avoid key opioids in patients who are ultrarapid or poor metabolizers of CYP2D6 to avoid toxicity and optimize efficacy. CASE REPORT: An older woman encountered a letter to the editor in a family magazine regarding genomically based responses to opioids. She reached out for more information and assistance, attesting to continued lack of analgesia to opioids prescribed during occasions of severe pain over the course of many years. A pharmacogenomic analysis proved to be the key to solving her mystery. CONCLUSION: Pharmacogenomic results may provide life-altering information transforming a patient's perspective on health care. Personalized medicine may be a key component in providing objective evidence for opioid treatment efficacy. There is a critical need for both provider and patient education to increase awareness of pharmacogenomics and how it can be applied to effective pharmacotherapy. Research is needed to explore appropriate, effective educational methods.

Humans↗