Abstract
BACKGROUND: Despite topiramate's ability to reduce heavy drinking, its adverse effects may limit its clinical utility. METHOD: To evaluate the risks and benefits of topiramate, we reanalyzed data from a completed trial of the medication in 138 heavy drinkers whose goal was to reduce their drinking to safe levels. We used the number of patients who had no heavy drinking days during the last 4 weeks of treatment to calculate topiramate's number needed to treat (NNT). To balance the risks and benefits of topiramate, we adjusted the NNT using 2 different levels of adverse event severity: moderate or greater (NNT-AEmod+) and severe or greater (NNT-AEsev+). This measure helps to guide the clinical use of topiramate in heavy drinkers by incorporating both its beneficial and adverse effects in a single measure. Because a polymorphism (rs2832407) in the gene encoding a kainate receptor subunit appears to moderate topiramate's effects in heavy drinkers, we repeated the analyses based on rs2832407 genotype (C-homozygote vs A-allele carrier) in the European American subsample (n = 122). RESULTS: Overall, the NNT for topiramate was 5.29, the NNT-AEmod+ was 7.52, and the NNT-AEsev+ was 6.12. Among European Americans with the rs2832407*CC genotype, the NNT was 2.28, the NNT-AEmod+ was 2.63, and the NNT-AEsev+ was 2.56. In contrast, for rs2832407*A-allele carriers, the NNT was 180.00, the NNT-AEmod+ was 322.16, and the NNT-AEsev+ was 217.45. CONCLUSIONS: In this sample of heavy drinkers, topiramate had a clinically important treatment effect that was most evident in European Americans with the rs2832407*CC genotype. In that group, in particular, it had a robust treatment effect, even when adjusted for adverse events. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00626925.