Objective: To critically examine the efficacy of bupropion SR for weight loss.

Research Methods and Procedures: This 24‐week multicenter, double‐blind, placebo‐controlled study randomized obese adults to placebo, bupropion SR 300, or 400 mg/d. Subjects were counseled on energy‐restricted diets, meal replacements, and exercise. During a 24‐week extension, placebo subjects were randomized to bupropion SR 300 or 400 mg/d in a double‐blinded manner.

Results: Of 327 subjects enrolled, 227 completed 24 weeks; 192 completed 48 weeks. Percentage losses of initial body weight for subjects completing 24 weeks were 5.0%, 7.2%, and 10.1% for placebo, bupropion SR 300, and 400 mg/d, respectively. Compared with placebo, net weight losses were 2.2% (p = 0.0468) and 5.1% (p < 0.0001) for bupropion SR 300 and 400 mg/d, respectively. The percentages of subjects who lost ≥5% of initial body weight were 46%, 59%, and 83% (p vs. placebo < 0.0001) for placebo, bupropion SR 300, and 400 mg/d, respectively; weight losses of ≥10% were 20%, 33%, and 46% (p vs. placebo = 0.0008) for placebo, bupropion SR 300, and 400 mg/d, respectively. Withdrawals, changes in pulse and blood pressure did not differ significantly from placebo at 24 weeks. Subjects who completed 48 weeks maintained mean losses of initial body weight of 7.5% and 8.6% for bupropion SR 300 and 400 mg/d, respectively.

Discussion: Bupropion SR 300 and 400 mg/d were well‐tolerated by obese adults and were associated with a 24‐week weight loss of 7.2% and 10.1% and sustained weight losses at 48 weeks.