Zonisamide for Weight Loss in Obese Adults: A Randomized Controlled Trial

CONTEXT: Zonisamide is a marketed antiepileptic drug that has serotonergic and dopaminergic activity in addition to blockade of sodium and calcium channels. Weight loss was an adverse effect associated with zonisamide treatment in epilepsy clinical trials. OBJECTIVE: To evaluate the efficacy of zonisamide for weight loss in obese adults. DESIGN AND SETTING: Sixteen-week randomized, double-blind, placebo-controlled trial with an optional single-blind extension of the same treatment for another 16 weeks, conducted at Duke University Medical Center from March 2001 to March 2002. PARTICIPANTS: Fifty-five (92%) women and 5 (8%) men (mean [SE] body mass index, 36.3 [0.5]; mean age, 37.0 (1.0) years). INTERVENTIONS: Patients were randomly assigned to receive zonisamide (n = 30) or placebo (n = 30). All participants were prescribed a balanced hypocaloric diet (500 kcal/d deficit) and compliance was monitored with self-rated food diaries. Zonisamide therapy was started at 100 mg/d orally, with gradual increase to 400 mg/d and further increase to 600 mg/d for patients losing less than 5% of body weight at the end of 12 weeks. Placebo dosing was identical. MAIN OUTCOME MEASURE: Change in body weight. RESULTS: Of the 60 randomized patients, 51 completed the 16-week acute phase. In an intent-to-treat analysis using the available data for all randomized participants with the last observation carried forward, the zonisamide group lost more body weight than the placebo group (mean [SE], 5.9 [0.8] kg [6.0% loss] vs 0.9 [0.4] kg [1.0% loss]; t = 5.5; P