Aims: We sought to evaluate the safety and efficacy of the GABAergic agent tiagabine in reducing cocaine use among methadone-treated patients.
Design: Ten-week randomized double-blind placebo-controlled trial.
Setting: Opiate Treatment Research Program, Veteran's Affairs Connecticut Healthcare System in West Haven, Connecticut, USA.
Participants: The participants were 45 cocaine-dependent methadone-treated patients who were predominately Caucasian (75.6%), male (77.8%) and never married (53%) with an average age of 38 years (SD = 6.5).
Interventions: Comparison groups received tiagabine 12 mg/day (n = 15), tiagabine 24 mg/day (n = 15) or placebo (n = 15).
Measures: Baseline assessments included the Structured Clinical Interview for DSM-IV, the Addiction Severity Index, a urine drug test, self-reported use and opiate withdrawal scales. Urine drug tests were performed thrice weekly.
Findings: Treatment retention was over 80% for all treatment groups. The sample mean (+/- SE) of cocaine-free urines for the first week after study entry and before tiagabine was started was 1.16 (0.19) urines/week. During weeks 9 and 10 cocaine-free urines increased significantly from baseline by 33% with high-dose tiagabine (24 mg/day), by 14% with low-dose tiagabine (12 mg/day) and decreased by 10% with placebo (hierarchical linear model, Z= 2.03; P < 0.05). Self-reported cocaine use also decreased significantly more with active medications than with placebo.
Conclusions: Tiagabine at 24 mg/day was well tolerated among these methadone-treated patients with only one reporting headache. Tiagabine appears to be a promising GABAergic medication that moderately improves cocaine-free urines.