Opium tincture versus methadone for opioid agonist treatment: a randomized controlled trial

AIM

To test if opium tincture (OT) was non-inferior to methadone in retaining participants in opioid agonist treatment (OAT).

DESIGN

A Phase III, multi-centre, parallel-group, non-inferiority, double-blind randomized controlled trial with an allocation ratio of 1:1. Participants were provided treatment and followed for a period of 85 days.

SETTING

Four OAT clinics in Iran.

PARTICIPANTS

Two hundred and four participants with opioid use disorder [mean age (standard deviation) = 37.4 (9.3); female 11.3%] recruited between July 2017 and January 2018.

INTERVENTIONS

Participants were assigned to either OT (102) or methadone (102) using a patient-centred flexible dosing strategy.

MEASUREMENTS

Treatment retention over 85 days was the primary outcome. Self-reported opioid use outside treatment and occurrence of adverse events (AEs) were the secondary outcomes.

FINDINGS

Remaining in treatment at the end of the follow-up were 68.6% in the methadone arm and 59.8% in the OT arm. The relative retention rate of methadone to OT was 1.15 (0.97, 1.36) in both intent-to-treat and per-protocol analyses; non-inferiority was not supported statistically, as the upper bound of the confidence interval exceeded our pre-specified non-inferiority margin (1.25). Opioid use outside treatment was reported by 30.3% of OT (n = 152) and 49.4% of methadone (n = 168) patients, a difference in proportions of -19%: 90% confidence interval (-28%, -10%). The total count of AEs in the OT arm (22 among nine individuals) was significantly higher (P = 0.04) than that in the methadone arm (three among two individuals). Nausea was the most common side effect.

CONCLUSION

While this study could not conclude the non-inferiority of opium tincture (OT) to methadone for retaining patients in opioid agonist treatment, OT retained 60% of participants to end of follow-up (85 days) and was superior to methadone in reducing self-reported opioid use outside treatment.

Morphine-3-Glucuronide, Physiology and Behavior

Morphine remains the gold standard painkiller available to date to relieve severe pain. Morphine metabolism leads to the production of two predominant metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). This metabolism involves uridine 5'-diphospho-glucuronosyltransferases (UGTs), which catalyze the addition of a glucuronide moiety onto the C3 or C6 position of morphine. Interestingly, M3G and M6G have been shown to be biologically active. On the one hand, M6G produces potent analgesia in rodents and humans. On the other hand, M3G provokes a state of strong excitation in rodents, characterized by thermal hyperalgesia and tactile allodynia. Its coadministration with morphine or M6G also reduces the resulting analgesia. Although these behavioral effects show quite consistency in rodents, M3G effects are much more debated in humans and the identity of the receptor(s) on which M3G acts remains unclear. Indeed, M3G has little affinity for mu opioid receptor (MOR) (on which morphine binds) and its effects are retained in the presence of naloxone or naltrexone, two non-selective MOR antagonists. Paradoxically, MOR seems to be essential to M3G effects. In contrast, several studies proposed that TLR4 could mediate M3G effects since this receptor also appears to be essential to M3G-induced hyperalgesia. This review summarizes M3G's behavioral effects and potential targets in the central nervous system, as well as the mechanisms by which it might oppose analgesia.

Influence of Morbid Obesity on the Pharmacokinetics of Morphine, Morphine-3-Glucuronide, and Morphine-6-Glucuronide

Introduction

Obesity is associated with many pathophysiological changes that may result in altered drug metabolism. The aim of this study is to investigate the influence of obesity on the pharmacokinetics of morphine, morphine-3-glucuronide (M3G), and morphine-6-glucuronide (M6G) through a combined analysis in morbidly obese patients and non-obese healthy volunteers.

Methods

In this analysis, data from 20 morbidly obese patients [mean body mass index 49.9 kg/m² (range 37.6–78.6 kg/m²) and weight 151.3 kg (range 112–251.9 kg)] and 20 healthy volunteers [mean weight 70.6 kg (range 58–85 kg)] were included. Morbidly obese patients received 10 mg of intravenous (I.V.) morphine after gastric bypass surgery, with additional morphine I.V. doses as needed. Healthy volunteers received an I.V. bolus of morphine of 0.1 mg/kg followed by an infusion of 0.030 mg kg⁻¹ h⁻¹ for 1 h. Population pharmacokinetic modeling was performed using NONMEM 7.2.

Results

In morbidly obese patients, elimination clearance of M3G and M6G was decreased substantially compared with healthy volunteers (p < 0.001). Regarding glucuronidation, only a slight decrease in the formation of M6G and a delay in the formation of M3G was found (both p < 0.001). Obesity was also identified as a covariate for the peripheral volume of distribution of morphine (p < 0.001).

Conclusion

Metabolism of morphine is not altered in morbidly obese patients. However, decreased elimination of both M3G and M6G is evident, resulting in a substantial increase in exposure to these two metabolites. A rational explanation of this finding is that it results from alterations in membrane transporter function and/or expression in the liver.

ClinicalTrials.gov identifier: NCT01097148.

Electronic supplementary material

The online version of this article (doi:10.1007/s40262-017-0544-2) contains supplementary material, which is available to authorized users.

Paracetamol and morphine for infant and neonatal pain; still a long way to go?

INTRODUCTION

Pharmacologic pain management in newborns and infants is often based on limited scientific data. To close the knowledge gap, drug-related research in this population is increasingly supported by the authorities, but remains very challenging. This review summarizes the challenges of analgesic studies in newborns and infants on morphine and paracetamol (acetaminophen). Areas covered: Aspects such as the definition and multimodal character of pain are reflected to newborn infants. Specific problems addressed include defining pharmacodynamic endpoints, performing clinical trials in this population and assessing developmental changes in both pharmacokinetics and pharmacodynamics. Expert commentary: Neonatal and infant pain management research faces two major challenges: lack of clear biomarkers and very heterogeneous pharmacokinetics and pharmacodynamics of analgesics. There is a clear call for integral research addressing the multimodality of pain in this population and further developing population pharmacokinetic models towards physiology-based models.