Smoking cessation drug shows promise for treating cannabis use disorder

A new randomized controlled trial has found promising evidence that the smoking cessation medication varenicline (Chantix/Champix) can help people with cannabis use disorder (CUD) to reduce cannabis use. CUD is a rising problem globally, partly due to recent legalization in several countries and US states, and until now no medications have been found to treat it. 

CUD is characterized by continued use of cannabis despite 'clinically significant impairment' such as ignoring important social, occupational, or recreational activities and persistent use despite physical or psychological problems associated with cannabis. Cannabis use is also associated with psychosis, sleep disorders, withdrawal, and mood and anxiety disorders.

Varenicline is an effective medication for quitting tobacco. This trial, conducted at the Medical University of South Carolina and published in Addiction, tested whether varenicline could help with CUD. Results showed it helped men reduce cannabis use, but not women. (Varenicline works equally well for both sexes as a stop-smoking aid.)

The trial included 174 participants with CUD who used cannabis at least three days per week. Participants were randomized to varenicline (working up to a dose of 1 mg twice daily) or placebo for 12 weeks. Participants also received a weekly brief medical management session to encourage their adherence to both the medication and the treatment plan.

The men in the study who received varenicline used cannabis fewer times per week than the men on placebo. Specifically, the varenicline group averaged 7.9 cannabis sessions per week during the study and 5.7 sessions in the week following the study, compared with more than 12 weekly sessions for the placebo group. The male varenicline group also used cannabis an average of 3.8 days per week, compared with 4.7 days per week for the male placebo group.

The women in the study who received varenicline did not differ in their cannabis use from the women on placebo. The varenicline group averaged just over 10 sessions per week, compared with the placebo group's 9.2 weekly sessions (which dropped to 8.2 in the week following the study). The female varenicline group used cannabis an average of 4.9 days per week, compared with 3.6 days for the female placebo group.

The female varenicline group showed higher withdrawal and craving scores and higher anxiety than any of the other groups. Perhaps connected with that, women receiving varenicline reported lower medication adherence than women receiving placebo.

Cannabis use disorder is rising quickly in the United States. Current pharmacological treatment options are very limited, and so our ability to help people reduce their cannabis use is also limited. Our study found that varenicline, a drug that helps people to reduce or stop smoking, may be effective at reducing cannabis use as well, but only for men. Our next step is to further explore varenicline for cannabis use disorder, using a larger sample size of women, to better understand this sex difference in the treatment outcome. In the meantime, we are encouraged that varenicline shows potential promise in treating this fast-growing problem."

Professor Aimee McRae-Clark, Lead Author