Topamax (topiramate) appears to be an effective and well tolerated treatment for alcohol abuse, according to a study in the Journal of the American Medical Association, potentially extending the franchise of J&J’s blockbuster beyond migraine and epilepsy.

The randomised controlled trial enrolled 371 alcohol dependent men and women aged 18 to 65 years. Subjects received up to 300mg/day of topiramate (mean dose 171mg) or placebo. All patients also received weekly psychosocial interventions that aimed to promote adherence.

Topiramate reduced the average percentage of heavy drinking days from 81.9% to 43.8% between baseline and week 14. In the placebo group, the percentage of heavy drinking days declined from 82.0% to 51.8% over the same time. The average difference between the groups was 16.2% and 8.4% depending on the statistical analysis used (i.e. not imputing missing data and imputing missing data with the baseline value respectively).

Two to three fold improvement in abstinence

Topiramate increased the likelihood of achieving 28 or more days of continuous non-heavy drinking between two and three fold compared with placebo (hazard ratio [HR] 2.28 and 2.79 in the imputed and non-imputed analyses respectively). Topiramate also increased the likelihood that the person would spend 28 or more days continuously abstinent between five and six fold (HR 5.03 and 5.96 respectively). Patients taking topiramate reached these endpoints more rapidly than those using placebo. Compared with placebo, topiramate reduced plasma levels of the liver enzyme gamma-glutamyl transferase (GGT), a laboratory measure of alcohol consumption. This suggests that topiramate reduces the number of drinks consumed each day.

Adverse events associated with topiramate included paresthesia, taste perversion, anorexia, and difficulty concentrating. Nevertheless, adherence was similar in the two groups: 91.5% for topiramate and 90.1% for placebo.

The authors note that non-specialist health practitioners can deliver topiramate and the brief psychosocial intervention. Therefore, a study examining efficacy in community practice settings is a logical next step. The authors concluded that “topiramate is a safe and consistently efficacious medication for treating alcohol dependence”.

In July, J&J revealed that sales of Topamax rose 16% in the second quarter of 2007 to $578 million. Analysts Spectra Intelligence estimates that the market for alcohol addiction medications was worth $125 million in 2005. They forecast growth to $840 million by 2012. The total potential market is at least 30 million people in the USA, Europe and Japan. Alcoholism imposes the third largest burden of disease in the USA and the fifth largest world wide.