Eight RCTs were included in the review (n=855). Study size ranged from 34 to 182 participants.
Sibutramine monotherapy was associated with greater weight loss compared with orlistat monotherapy (WMD -2.2kg, 95% CI -3.9 to -0.5, p=0.000, seven RCTs). Significant heterogeneity was detected (I2=82.9%); after excluding the two studies of type 2 diabetes and hypertension, there was no significant heterogeneity.
Combination therapy was as associated with greater weight loss as orlistat alone in two studies (-10.8 versus -5.5kg and -13.7 versus -9.4kg), but was not found to be better than sibutramine alone (-10.8 versus -10.1kg and -13.7 versus -11.7kg). The funnel plot and Egger's test did not indicate the presence of publication bias.
Three of the four studies that reported dropout data reported lower risk of dropout with sibutramine than orlistat, but the differences were not statistically significant. Funding source was not reported in six studies.