Comparison of the effects of sibutramine versus sibutramine plus metformin in obese women

Sibutramine and metformin are drugs commonly used to obtain weight loss. We aimed to compare the effects of sibutramine alone with that of sibutramine plus metformin combination on weight loss, insulin sensitivity, leptin and C reactive protein in obese women. Seventy obese women were included. After a diet period of month (baseline), each individual was randomly assigned to receive 15 mg sibutramine (sibutramine group; n = 36) or 15 mg sibutramine plus 1,700 mg metformin per day (sibutramine plus metformin group; n = 34) during the next 12 months. Body weight, insulin resistance by the homeostasis model assessment model (HOMA-IR), leptin and C reactive protein were measured at baseline, after 3 months and after 12 months. Mean weight losses in sibutramine and sibutramine plus metformin groups were 5.3 ± 4.0% (P < 0.001) and 6.8 ± 3.9% (P < 0.001) after 3 months, and 10.5 ± 4.4% (P < 0.001) and 15.7 ± 4.6% (P = 0.007) after 12 months, respectively. HOMA-IR value also decreased in both sibutramine (P = 0.045 and P = 0.002) and sibutramine plus metformin groups (P = 0.04 and P = 0.015) after 3 and 12 months, respectively. Similarly, serum leptin levels decreased in both sibutramine (P = 0.04, P = 0.01) and sibutramine plus metformin groups (P = 0.023, P = 0.025) after 3 and 12 months, respectively. There was also significant reductions in serum C reactive protein levels in both sibutramine (P = 0.045, P = 0.02) and sibutramine plus metformin groups (P = 0.007, P = 0.001) after 3 and 12 months, respectively. These decrements of body weight, HOMA-IR, serum leptin and C reactive protein levels were not statistical significance between these two groups both after 3 and 12 months (P > 0.05). Combination of sibutramine with metformin did not result in any further effects on weight loss, insulin resistance, leptin and C reactive protein levels when compared to sibutramine alone.