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Recent evidence suggests that chronic exposure to opioid analgesics such as morphine disrupts the intestinal epithelial layer and causes intestinal dysbiosis. Depleting gut bacteria can preclude the development of tolerance to opioid-induced antinociception, suggesting an important role of the gut-brain axis in mediating opioid effects. The mechanism underlying opioid-induced dysbiosis, however, remains unclear. Host-produced antimicrobial peptides (AMPs) are critical for the integrity of the intestinal epithelial barrier as they prevent the pathogenesis of the enteric microbiota. Here, we report that chronic morphine or fentanyl exposure reduces the antimicrobial activity in the ileum, resulting in changes in the composition of bacteria. Fecal samples from morphine-treated mice had increased levels of Akkermansia muciniphila with a shift in the abundance ratio of Firmicutes and Bacteroidetes. Fecal microbial transplant (FMT) from morphine-naïve mice or oral supplementation with butyrate restored (a) the antimicrobial activity, (b) the expression of the antimicrobial peptide, Reg3γ, (c) prevented the increase in intestinal permeability and (d) prevented the development of antinociceptive tolerance in morphine-dependent mice. Improved epithelial barrier function with FMT or butyrate prevented the enrichment of the mucin-degrading A. muciniphila in morphine-dependent mice. These data implicate impairment of the antimicrobial activity of the intestinal epithelium as a mechanism by which opioids disrupt the microbiota-gut-brain axis., (© 2024 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)

Neonatal drug exposure is currently assessed using meconium, urine, blood, hair, or umbilical cord tissue/blood. Due to the invasiveness, challenges, and limitations of collection, and/or analytical difficulties of these matrices, oral fluid may be a more desirable matrix in diagnosing opioid exposure and risk for opioid withdrawal in neonatal abstinence syndrome. Traditional oral fluid collection devices are not viable options as they are too large for neonates' mouths and may contain chemicals on the collection pad. Unstimulated and stimulated infant oral fluid samples have been used for therapeutic drug monitoring as an alternative matrix to blood. The objective of this study was to assess the viability of a simple oral fluid collection system using a sterile foam-tipped swab rinsed in phosphate-buffered saline. Two infants were administered fentanyl for post-operative pain relief while hospitalized in the Neonatal Intensive Care Units at the Children's Hospital of Richmond of Virginia Commonwealth University. Oral fluid samples were collected at 16 h, 2 days, and/or 7 days following the start of intravenous infusion of fentanyl. Samples were analyzed by ultra-high-pressure liquid chromatography-tandem mass spectrometry for fentanyl and norfentanyl after solid-phase extraction. In one of the three samples tested, fentanyl and norfentanyl were detected at concentrations of 28 and 78 ng/mL, respectively. Based on the infusion rate, the theoretical oral fluid fentanyl concentration at steady state was calculated to be 33 ng/mL., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: One emerging strategy to address the opioid crisis includes opioid-targeted immunopharmacotherapies. This study compared effectiveness of a heroin-tetanus toxoid (TT) conjugate vaccine to antagonize heroin, 6-acetylmorphine (6-AM), morphine, and fentanyl antinociception in rats., Methods: Adult male and female Sprague Dawley rats received three doses of active or control vaccine at weeks 0, 2, and 4. Vaccine pharmacological selectivity was assessed by comparing opioid dose-effect curves in 50 °C  warm-water tail-withdrawal procedure before and after active or control heroin-TT vaccine. Route of heroin administration [subcutaneous (SC) vs. intravenous [IV)] was also examined as a determinant of vaccine effectiveness. Continuous naltrexone treatment (0.0032-0.032 mg/kg/h) effects on heroin, 6-AM, and morphine antinociceptive potency were also determined as a benchmark for minimal vaccine effectiveness., Results: The heroin-TT vaccine decreased potency of SC heroin (5-fold), IV heroin (3-fold), and IV 6-AM (3-fold) for several weeks without affecting IV morphine or SC and IV fentanyl potency. The control vaccine did not alter potency of any opioid. Naltrexone dose-dependently decreased antinociceptive potency of SC heroin, and treatment with 0.01 mg/kg/h naltrexone produced similar, approximate 8-fold decreases in potencies of SC and IV heroin, IV 6-AM, and IV morphine. The combination of naltrexone and active vaccine was more effective than naltrexone alone to antagonize SC heroin but not IV heroin., Conclusions: The heroin-TT vaccine formulation examined is less effective, but more selective, than chronic naltrexone to attenuate heroin antinociception in rats. Furthermore, these results provide an empirical framework for future preclinical opioid vaccine research to benchmark effectiveness against naltrexone., (Copyright © 2019 Elsevier B.V. All rights reserved.)

One proposed factor contributing to the increased frequency of opioid overdose deaths is the emergence of novel synthetic opioids, including illicit fentanyl and fentanyl analogues. A treatment strategy currently under development to address the ongoing opioid crisis is immunopharmacotherapies or opioid-targeted vaccines. The present study determined the effectiveness and selectivity of a fentanyl-tetanus toxoid conjugate vaccine to alter the behavioral effects of fentanyl and a structurally dissimilar mu-opioid agonist oxycodone in male rhesus monkeys (n = 3-4). Fentanyl and oxycodone produced dose-dependent suppression of behavior in an assay of schedule-controlled responding and antinociception in an assay of thermal nociception (50 °C). Acute naltrexone (0.032 mg/kg) produced an approximate 10-fold potency shift for fentanyl to decrease operant responding. The fentanyl vaccine was administered at weeks 0, 2, 4, 9, 19, and 44 and fentanyl or oxycodone potencies in both behavioral assays were redetermined over the course of 49 weeks. The vaccine significantly and selectively shifted fentanyl potency at least 10-fold in both assays at several time points over the entire experimental period. Mid-point titer levels correlated with fentanyl antinociceptive potency shifts. Antibody affinity for fentanyl as measured by a competitive binding assay improved over time to approximately 3-4 nM. The fentanyl vaccine also increased fentanyl plasma levels approximately 6-fold consistent with the hypothesis that the vaccine sequesters fentanyl in the blood. Overall, these results support the continued development and evaluation of this fentanyl vaccine in humans to address the ongoing opioid crisis., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Opioid usage in the USA has increased over the past decade, with prescriptions increasing from 76 million in 1991 to 207 million in 2013. New regulations have curbed the number of prescriptions, leading to an increase in heroin use. Heroin-related overdoses have quadrupled between 2000 and 2015. The traditional urinary biomarkers for indicating heroin use are a combination of morphine and 6-acetyl morphine (6-AM). Morphine is detectable in urine for several days. 6-AM is detected in urine for 2–8 hours. Papaverine has been proposed as an alternative heroin biomarker. It has been reported to have a 1–2 day detection window. Papaverine metabolites have been reported to have up to a 3-day detection window. Presented is a method for the detection of papaverine and its metabolites, 6-desmethyl papaverine (6-DMP) and 4′, 6-didesmethyl papaverine (4,6-DDMP), in urine using a modified Waters® MCX™ microelution method. An ultra-performance liquid chromatography and tandem mass spectrometry (UPLC–MS-MS), with a Waters' BEH C18 column, and 20 mM ammonium formate water: 20 mM ammonium formate methanol mobile phase was employed. Calibration curves were linear from 0.1 to 50 ng/mL. No interferences were observed from the analysis of multicomponent therapeutic drug or drugs of abuse control materials; intra- and inter-run precision tests were acceptable. A total of 428 genuine urine specimens where heroin use was suspected were analyzed. These included 101 6-AM and 179 morphine only positive samples as well as 6 morphine-negative samples where papaverine and/or metabolites were detected. The determined concentrations in these samples for papaverine, 6-DMP and 4,6-DDMP ranged from 0.10 to 994, 0.10 to 462 and 0.12 to 218 ng/mL, respectively. The method was rugged and robust for the analysis of papaverine and metabolites, 6-DMP and 4,6-DDMP. The use papaverine and metabolites, 6-DMP and 4,6-DDMP has the potential to increase the detection window of heroin use. [ABSTRACT FROM AUTHOR]

Opioid-sparing adjuncts are treatments that aim to reduce the overall dose of opioids needed to achieve analgesia, hence decreasing the burden of side effects through alternative mechanisms of action. Lorcaserin is a serotonin 5-HT 2C receptor (5-HT 2C R) agonist that has recently been reported to reduce abuse-related effects of the opioid analgesic oxycodone. The goal of our studies was to evaluate the effects of adjunctive lorcaserin on opioid-induced analgesic-like behavior using the tail-flick reflex (TFR) test as a mouse model of acute thermal nociception. We show that whereas subcutaneous (s.c.) administration of lorcaserin alone was inactive on the TFR test, adjunctive lorcaserin (s.c.) significantly increased the potency of oxycodone as an antinociceptive drug. This effect was prevented by the 5-HT 2C R antagonist SB242084. A similar lorcaserin (s.c.)-induced adjunctive phenotype was observed upon administration of the opioid analgesics morphine and fentanyl. Remarkably, we also show that, opposite to the effects observed via s.c. administration, intrathecal (i.t.) administration of lorcaserin alone induced antinociceptive TFR behavior, an effect that was not prevented by the opioid receptor antagonist naloxone. This route of administration (i.t.) also led to a significant augmentation of oxycodone-induced antinociception. Lorcaserin (s.c.) did not alter the brain or blood concentrations of oxycodone, which suggests that its adjunctive effects on opioid-induced antinociception do not depend upon changes in opioid metabolism. Together, these data indicate that lorcaserin-mediated activation of the 5-HT 2C R may represent a new pharmacological approach to augment opioid-induced antinociception. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'. • Intrathecal administration of lorcaserin induces antinociception whereas subcutaneous injection lacks antinociceptive effect. • Adjunctive subcutaneous administration of lorcaserin augments opioid-induced antinociception. • These included oxycodone, morphine and fentanyl. • Adjunctive antinociceptive effect of lorcaserin is prevented by a 5-HT 2C receptor antagonist. • Lorcaserin may serve as a new approach to augment opioid-induced analgesia. [ABSTRACT FROM AUTHOR]