No evidence for reduction of opioid-withdrawal symptoms by cannabis smoking during a methadone dose taper

Background and Objectives: To support medication development with cannabinoids, smoked cannabis has been said to alleviate symptoms of opioid withdrawal. We evaluated that hypothesis. Methods: We analyzed data from the methadone-taper phase of a clinical trial we had conducted. Participants were 116 outpatient heroin and cocaine users (of whom 46 were also cannabis users) who stayed for the 10-week taper. Main outcome measures were weekly urine screens for cannabinoids, plus every-two-week assessments of opioid-withdrawal symptoms. Results: Opioid-withdrawal scores did not differ overall between users and nonusers of cannabis. In a lagged analysis in the 46 users, there was a slight (not statistically significant) indication that weeks of higher opiate-withdrawal symptoms preceded weeks of cannabis use (effect-size r=.20, 95% CI -.10 to.46, p=.52). Even if this finding is taken to suggest self-medication with cannabis, a lagged analysis in the other temporal direction showed no indication that cannabis use predicted lower opiate-withdrawal symptoms the next week (effect-size r=.01, 95% CI -.28 to.30, p=.69). These findings persisted in sensitivity analyses controlling for each of 17 potential confounds. Discussion and Conclusion With our findings, the clinical evidence for smoked cannabis as a reducer of opioid-withdrawal symptoms moves slightly further from "inconclusive" or "mixed" and closer to negative, at least in the context of a methadone dose taper like the one used here. Scientific Significance This finding may remove one rationale for medication development using cannabinoids to treat opioid withdrawal, but leaves other rationales intact. (Am J Addict 2015;XX: XX-XX)