Efficacy and Safety Study of Combination Therapy to Treat Uncomplicated Obesity

A completed proof of concept study, OT-101 (Data on File, Orexigen Therapeutics, 2005), demonstrated that a combination of 300 mg bupropion SR and 50 mg naltrexone was associated with greater weight loss than bupropion SR alone, naltrexone alone, or placebo in subjects with uncomplicated obesity. The hypothesis for the current trial is that by adjusting the doses and titration schedules of bupropion SR and naltrexone greater efficacy and improved tolerability can be achieved. In this trial, a higher dose of bupropion and 2 lower doses of naltrexone than utilized in the previous trial (OT-101) will be evaluated. The doses of both drugs will be titrated over 4 weeks and administered twice a day. There are 2 cohorts. At each site, cohort 2 recruitment began as soon as cohort 1 enrollment was completed. Cohort 1 treatment groups are (60 per group): * Group 1: Bupropion SR (400 mg/day) plus Naltrexone (48 mg/day) * Group 2: Bupropion SR (400 mg/day) plus Naltrexone (16 mg/day) * Group 3: Bupropion SR (400 mg/day) plus N-Placebo * Group 4: B-placebo plus Naltrexone (48 mg/day) * Group 5: B-Placebo plus N-Placebo Cohort treatment 2 Groups are: * Group 6: B-Placebo plus N-Placebo (n=20) * Group 7: Bupropion SR (400 mg/day) plus Naltrexone (32 mg/day)(n=60)