Mechanism of opioid addiction and its intervention therapy: Focusing on the reward circuitry and mu‐opioid receptor

Postoperative Multimodal Analgesia Strategy for Enhanced Recovery After Surgery in Elderly Colorectal Cancer Patients

Enhanced Recovery After Surgery (ERAS) protocols have substantially proven their merit in diminishing recuperation durations and mitigating postoperative adverse events in geriatric populations undergoing colorectal cancer procedures. Despite this, the pivotal aspect of postoperative pain control has not garnered the commensurate attention it deserves. Typically, employing a multimodal analgesia regimen that weaves together nonsteroidal anti-inflammatory drugs, opioids, local anesthetics, and nerve blocks stands paramount in curtailing surgical complications and facilitating reduced convalescence within hospital confines. Nevertheless, this integrative pain strategy is not devoid of pitfalls; the specter of organ dysfunction looms over the geriatric cohort, rooted in the abuse of analgesics or the complex interplay of polypharmacy. Revolutionary research is delving into alternative delivery and release modalities, seeking to allay the inadvertent consequences of analgesia and thereby potentially elevating postoperative outcomes for the elderly post-colorectal cancer surgery populace. This review examines the dual aspects of multimodal analgesia regimens by comparing their established benefits with potential limitations and offers insight into the evolving strategies of drug administration and release.

Pharmacogenetics of Biochemically Verified Abstinence in an Opioid Agonist Therapy Randomized Clinical Trial of Methadone and Buprenorphine/Naloxone

Methadone and buprenorphine/naloxone are opioid agonist therapies for opioid use disorder treatment. Genetic factors contribute to individual differences in opioid response; however, little is known regarding genetic associations with clinical outcomes in people receiving opioid agonist therapies. Participants diagnosed with opioid use disorder, principally consisting of prescription opioids (licit or illicit), were randomized to methadone or buprenorphine/naloxone for 24 weeks of daily treatment (NCT03033732). Urine was collected at 12 biweekly study visits and analyzed for non-treatment opioids. Variants in genes involved in methadone metabolism (CYP2B6, CYP2C19, and CYP3A4), buprenorphine metabolism (CYP3A4 and UGT2B7), and μ-opioid receptor function (OPRM1) were genotyped and analyzed for their association with the number of non-treatment opioid-free urine screens. Primary analyses focused on the last 12 weeks (6 study visits, post-titration) of treatment among those reporting White ethnicity. Additional sensitivity and exploratory analyses were performed. Among methadone-treated participants (n = 52), the OPRM1 rs1799971 AA genotype (vs. G-genotypes, i.e., having one or two G alleles) was associated with greater opioid-free urine screens (incidence rate ratio = 5.24, 95% confidence interval (CI) = 2.43-11.26, P = 0.000023); longitudinal analyses showed a significant genotype-by-time interaction over the full 24 weeks (12 study visits, β = -0.28, 95% CI = -0.45 to -0.11, P = 0.0015). Exploratory analyses suggest an OPRM1 rs1799971 genotype effect on retention. No evidence of association was found between other genetic variants, including in metabolic variants, and non-treatment opioid-free urine screens in the methadone or buprenorphine/naloxone arms. Those with the OPRM1 rs1799971 G-genotypes may have a poorer response to methadone maintenance treatment, an effect that persisted through 24 weeks of treatment.

Fentanyl-induced reward seeking is sex and dose dependent and is prevented by D-cysteine ethylester

Introduction: Despite their inclination to induce tolerance, addictive states, and respiratory depression, synthetic opioids are among the most effective clinically administered drugs to treat severe acute/chronic pain and induce surgical anesthesia. Current medical interventions for opioid-induced respiratory depression (OIRD), wooden chest syndrome, and opioid use disorder (OUD) show limited efficacy and are marked by low success in the face of highly potent synthetic opioids such as fentanyl. D-Cysteine ethylester (D-CYSee) prevents OIRD and post-treatment withdrawal in male/female rats and mice with minimal effect on analgesic status. However, the potential aversive or rewarding effects of D-CYSee have yet to be fully characterized and its efficacy could be compromised by interactions with opioid-reward pathology. Methods: Using a model of fentanyl-induced conditioned place preference (CPP), this study evaluated 1) the dose and sex dependent effects of fentanyl to induce rewarding states, and 2) the extent to which D-CYSee alters affective state and the acquisition of fentanyl-induced seeking behaviors. Results: Fentanyl reward-related effects were found to be dose and sex dependent. Male rats exhibited a range-bound dose response centered at 5 µg/kg. Female rats exhibited a CPP only at 50 µg/kg. This dose was effective in 25% of females with the remaining 75% showing no significant CPP at any dose. Pretreatment with 100 mg/kg, but not 10 mg/kg, D-CYSee prevented acquisition of fentanyl seeking in males while both doses were effective at preventing acquisition in females. Discussion: These findings suggest that D-CYSee is an effective co-treatment with prescribed opioids to reduce the development of OUD.