Despite the widespread use of polypharmacy, the management of hepatitis C virus (HCV) treatment-related side-effects is often incomplete, and many patients turn to cannabis for symptom relief. Unfortunately, there are few data about cannabis use on treatment outcomes, leaving clinicians without the data needed to inform recommendations.
To define the impact of cannabis use during HCV treatment, we conducted a prospective observational study of standard interferon and ribavirin treatment in 71 recovering substance users, of whom 22 (31%) used cannabis and 49 (69%) did not.
Seventeen of the 71 study patients (24%) discontinued therapy early, one cannabis user (5%) and 16 non-users (33%) (P=0.01). Overall, 37 patients (52%) were end-of-treatment responders, 14 (64%) cannabis users and 23 (47%) non-users (P=0.21). A total of 21 out of 71 (30%) had a sustained virological response: 12 of the 22 cannabis users (54%) and nine of the 49 non-users (18%) (P=0.009), corresponding to a post-treatment virological relapse rate of 14% in the cannabis users and 61% in the non-users (P=0.009). Overall, 48 (68%) were adherent, 29 (59%) non-users and 19 (86%) cannabis users (P=0.03). Although cannabis users were no more likely than non-users to take at least 80% of the prescribed interferon or ribavirin, they were significantly more likely to remain on HCV treatment for at least 80% of the projected treatment duration, 95 versus 67% (P=0.01).
Our results suggest that modest cannabis use may offer symptomatic and virological benefit to some patients undergoing HCV treatment by helping them maintain adherence to the challenging medication regimen.