Additional beneficial effects on 'cardiometabolic risk factors' beyond those expected from weight loss in trials of the anti-obesity drug rimonabant may not be due to the drug itself, reports an article in the June issue of Drug and Therapeutics Bulletin (DTB).
Advertisements for rimonabant (sold under the brand name Acomplia by Sanofi-Aventis) claim that 'an estimated 50% of the effects ... on cardiometabolic risk factors are beyond those expected from weight loss alone'. But DTB argues that these effects are not proven to be due to the drug itself.
Also, no published trials have compared rimonabant with either of the other anti-obesity drugs orlistat or sibutramine. Instead, rimonobant's effects on weight have been assessed in four double-blind trials comparing the drug with placebo.
The article says: "In three of the trial reports, the authors state that the effects of rimonabant on HDL, triglycerides and HBA1c were partly independent of weight loss. However, it is not proven that any independent effect is wholly or partially attributable to rimonabant."
The article suggests that these observed effects might be related to increased activity based on the lifestyle advice given to participants at the start of the trials.
"Furthermore, it is not known whether rimonabant's effects on individual risk factors translate into a reduced long-term likelihood of cardiovascular events," the article adds.
"Rimonabant has not been directly compared with other, less expensive, drug treatments for obesity. Orlistat is the drug for obesity for which there is the most evidence for efficacy and safety to date, and we have previously concluded that it is a reasonable option for obese patients where diet and exercise and/or behavioural measures alone have failed."
Rimonabant is the most expensive of the anti-obesity drugs. A year's treatment with rimonabant 20mg daily costs the NHS around £720, compared with £520 for orlistat 120 mg three times daily and £480-570 for sibutramine 10-15 mg daily.