Pharmacodynamic Effects of Sibutramine on Gastric Function in Obesity

Inclusion Criteria Normal weight, overweight and obese subjects with BMI> 18 Kg/m2 residing in Olmsted County, MN: Otherwise healthy individuals who are not currently on treatment for cardiac, pulmonary, gastrointestinal, hepatic, renal, hematological, neurological, endocrine (other than hyperglycemia not requiring medical therapy) and unstable psychiatric disease. Age: 18-65 years Gender: Men or women. Women of childbearing potential will have negative pregnancy test within 48 h of enrollment and before each radiation exposure. Exclusion Criteria Weight exceeding 300 pounds or 137 kilograms (due to limitations regarding SPECT imaging studies). Abdominal surgery other than appendectomy, Caesarian section or tubal ligation. Positive history of chronic gastrointestinal diseases, systemic disease that could affect gastrointestinal motility or use of medications that may alter gastrointestinal motility, appetite or absorption e.g., orlistat (Xenical). Significant psychiatric dysfunction based upon screening with the Hospital Anxiety and Depression Scale [HADS] self-administered alcoholism screening test (substance abuse) and the questionnaire on eating and weight patterns (binge eating disorders and bulimia). If such a dysfunction is identified by a HADS score >8 or difficulties with substance or eating disorders, the participant will be excluded and given a referral letter to his/her primary care doctor for further appraisal and follow-up. Intake of medication, whether prescribed or OTC medication (except multivitamins) within 7 days of the study. Exceptions are birth control pill, estrogen replacement therapy, and thyroxine replacement. Concomitant use of MAOI inhibitors and other centrally acting appetite suppressants (since this would make them ineligible for sibutramine treatment). Hypersensitivity to sibutramine (since this would make them ineligible for sibutramine treatment).