Sibutramine is a serotonin and noradrenaline re-uptake inhibitor (SNRI) which induces weight loss via a dual mode of action: enhancing both satiety and energy expenditure. Sibutramine exerts its in vivo effects predominantly via its secondary and primary amine metabolites. Following oral ingestion, sibutramine is well absorbed and undergoes extensive first pass metabolism. Sibutramine produces statistically and clinically significant, dose-related weight loss over the range 5-30 mg once daily; active weight loss occurs for 6 months. Long-term studies of up to 1 year have found that weight loss is maintained with continued sibutramine therapy. Sibutramine-induced weight loss is associated with beneficial changes in obesity-related risk factors, such as serum lipids, uric acid levels, and glycaemic control (in patients with type 2 diabetes). Subcutaneous/visceral fat ratio was found to increase significantly under sibutramine treatment, indicating that relatively more visceral fat than subcutaneous fat is lost. Sibutramine is well tolerated; side-effects are generally mild, non-treatment limiting, and consistent with the known mechanism of action of the drug. Overall, studies have found sibutramine to be an effective weight loss agent with a good safety profile.