Fifteen RCTs (n=1,236) were included in the review. Sample sizes ranged between 30 and 183. Nine studies scored 4 on the Jadad scale and six studies scored 3. Approximately 50% of the included patients were lost to follow-up. Treatment duration in the trials ranged from eight to 13 weeks.
There were no differences in retention of patients in treatment programmes with use of anticonvulsant medication compared to placebo (RR 0.97, 95% CI 0.86 to 1.09; n=899). No statistical heterogeneity was reported (I2=0%). No particular anticonvulsant was found to be efficacious in terms of enhancing patient retention in treatment; gabapentin was found to have a detrimental effect on retention (RR 3.48, 95% CI 1.04 to 11.73; n=80).
There were no significant differences in cocaine use after treatment with anticonvulsant medication compared with placebo. In one small study that evaluated use of topiramate, the intervention was found to have benefits on cocaine use at the end of treatment (RR 0.61, 95% CI 0.40 to 0.93; n=40).