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.