Topiramate (Topamax)—along with exercise and a reduced-calorie diet—can help lower weight and blood sugar in obese adults with type 2 diabetes, a Swedish trial reveals. Indicated for epilepsy and migraine, the drug is not FDA-approved for weight loss, though it is sometimes used off-label for this purpose.

In a trial at a university hospital in Göteborg, 541 diabetics aged 18-76 years with a mean weight of 103.7 kg were randomized to placebo, topiramate 96 mg/day, or topiramate 192 mg/day. All participants were instructed to follow a weight-loss program that included diet, exercise, and behavior modification.

After 40 weeks, the topiramate 96-mg/day and 192-mg/day groups had lost 6.6% and 9.1% of their baseline body weight, respectively. In contrast, the placebo group lost 2.5%. The topiramate patients also had significant reductions in hemoglobin A1c levels—0.6% in the 96-mg group and 0.7% in the 192-mg group. Those on placebo had a reduction of 0.2%.

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Paresthesia was observed in 46% of all topiramate-treated patients, compared with 21% in the placebo group. Overall incidence of withdrawal due to adverse events was 12% in the placebo group and 17% and 21% in the two topiramate groups. Serious adverse events were observed in 6% of the topiramate subjects, and 4% of placebo subjects.

The researchers offer speculation that topiramate “is associated with several neuronal effects, including inhibition of kainate-evoked neuronal membrane currents that may potentially reduce appetite and/or food intake” (Diabetes Obes Metab. 2007;9:360-368). The study was sponsored by the drug’s manufacturer, Johnson & Johnson.