A proof-of-concept randomized controlled study of gabapentin: effects on cannabis use, withdrawal and executive function deficits in cannabis-dependent adults

Abstract

There are no FDA-approved pharmacotherapies for cannabis dependence. Cannabis is the most widely used illicit drug in the world, and patients seeking treatment for primary cannabis dependence represent 25% of all substance use admissions. We conducted a phase IIa proof-of-concept pilot study to examine the safety and efficacy of a calcium channel/GABA modulating drug, gabapentin, for the treatment of cannabis dependence. A 12-week, randomized, double-blind, placebo-controlled clinical trial was conducted in 50 unpaid treatment-seeking male and female outpatients, aged 18-65 years, diagnosed with current cannabis dependence. Subjects received either gabapentin (1200 mg/day) or matched placebo. Manual-guided, abstinence-oriented individual counseling was provided weekly to all participants. Cannabis use was measured by weekly urine toxicology and by self-report using the Timeline Followback Interview. Cannabis withdrawal symptoms were assessed using the Marijuana Withdrawal Checklist. Executive function was measured using subtests from the Delis-Kaplan Executive Function System. Relative to placebo, gabapentin significantly reduced cannabis use as measured both by urine toxicology (p=0.001) and by the Timeline Followback Interview (p=0.004), and significantly decreased withdrawal symptoms as measured by the Marijuana Withdrawal Checklist (p<0.001). Gabapentin was also associated with significantly greater improvement in overall performance on tests of executive function (p=0.029). This POC pilot study provides preliminary support for the safety and efficacy of gabapentin for treatment of cannabis dependence that merits further study, and provides an alternative conceptual framework for treatment of addiction aimed at restoring homeostasis in brain stress systems that are dysregulated in drug dependence and withdrawal.

Figure 1

CONSORT flow diagram.

Figure 2

Effects of gabapentin vs placebo on cannabis use measures over the 12-week course of treatment (bars=SEM). (a) Grams of marijuana smoked per week and corresponding CN-THCCOOH ratios. Inset: Details for weeks 9 through 12. (b) Days per week of marijuana use.

Figure 3

Effects of gabapentin vs placebo on cannabis withdrawal variables over the 12-week course of treatment (bars=SEM). (a) Median number of Marijuana Withdrawal Checklist items endorsed on study. (b) Mean Pittsburgh Sleep Quality Index total scores. (c) Mean marijuana craving scores. (d) Beck Depression Inventory-II scores.

Figure 4

Change scores on Delis–Kaplan Executive Function System tests from baseline to week 4. Individual subtest scores were not significantly different between groups; however, mean improvement on composite scores was significantly better for gabapentin vs placebo (t=−2.4, df=15, p=0.029). Higher scores (>0) indicate greater improvement.