Fine-grain analysis of the treatment effect of topiramate on methamphetamine addiction with latent variable analysis.

BACKGROUND: As reported previously, 140 methamphetamine-dependent participants at eight medical centers in the U.S. were assigned randomly to receive topiramate (N=69) or placebo (N=71) in a 13-week clinical trial. The study found that topiramate did not appear to reduce methamphetamine use significantly for the primary outcome (i.e., weekly abstinence from methamphetamine in weeks 6-12). Given that the treatment responses varied considerably among subjects, the objective of this study was to identify the heterogeneous treatment effect of topiramate and determine whether topiramate could reduce methamphetamine use effectively in a subgroup of subjects. METHODS: Latent variable analysis was used for the primary and secondary outcomes during weeks 6-12 and 1-12, adjusting for age, sex, and ethnicity. RESULTS: Our analysis of the primary outcome identified 30 subjects as responders, who either reduced methamphetamine use consistently over time or achieved abstinence. Moreover, topiramate recipients had a significantly steeper slope in methamphetamine reduction and accelerated to abstinence faster than placebo recipients. For the secondary outcomes in weeks 6-12, we identified 40 subjects as responders (who had significant reductions in methamphetamine use) and 65 as non-responders; topiramate recipients were more than twice as likely as placebo recipients to be responders (odds ratio=2.67; p=0.019). Separate analyses of the outcomes during weeks 1-12 yielded similar results. CONCLUSIONS: Methamphetamine users appear to respond to topiramate treatment differentially. Our findings show an effect of topiramate on the increasing trend of abstinence from methamphetamine, suggesting that a tailored intervention strategy is needed for treating methamphetamine addiction.

Topiramate for the treatment of methamphetamine addiction: a multi-center placebo-controlled trial.

AIMS: Topiramate has shown efficacy at facilitating abstinence from alcohol and cocaine abuse. This double-blind, placebo-controlled out-patient trial tested topiramate for treating methamphetamine addiction. DESIGN: Participants (n = 140) were randomized to receive topiramate or placebo (13 weeks) in escalating doses from 25 mg/day [DOSAGE ERROR CORRECTED] to the target maintenance of 200 mg/day in weeks 6-12 (tapered in week 13). Medication was combined with weekly brief behavioral compliance enhancement treatment. SETTING: The trial was conducted at eight medical centers in the United States. PARTICIPANTS: One hundred and forty methamphetamine-dependent adults took part in the trial. MEASUREMENTS: The primary outcome was abstinence from methamphetamine during weeks 6-12. Secondary outcomes included use reduction versus baseline, as well as psychosocial variables. FINDINGS: In the intent-to-treat analysis, topiramate did not increase abstinence from methamphetamine during weeks 6-12. For secondary outcomes, topiramate reduced weekly median urine methamphetamine levels and observer-rated severity of dependence scores significantly. Subjects with negative urine before randomization (n = 26) had significantly greater abstinence on topiramate versus placebo during study weeks 6-12. Topiramate was safe and well tolerated. CONCLUSIONS: Topiramate does not appear to promote abstinence in methamphetamine users but can reduce the amount taken and reduce relapse rates in those who are already abstinent.