Long-term drug pharmacotherapy for obesity and overweight

This review assessed the long-term benefits and risks of approved anti-obesity drugs in clinical trials of 1 to 4 years duration. Sixteen orlistat (10,631 patients), 10 sibutramine (2623 patients) and four rimonabant (6635 patients) studies were examined. High drop-out rates (30% to 40%) were a limitation of nearly all studies. Compared to placebo, all three drugs reduced weight by around five kg or less and orlistat reduced the number of high-risk patients who developed diabetes. No data to show that any of the three drugs lowers the risk of death or cardiovascular disease were found. The most prominent side effects were gastrointestinal for orlistat, cardiovascular for sibutramine (raised blood pressure and/or pulse rate) and psychiatric for rimonabant (mood disorders). In Europe, rimonabant is contraindicated for patients with severe depression and/or patients who are treated with antidepressive medications. Rimonabant is furthermore not recommended for patients with other untreated psychiatric conditions.
We conclude that: 1. average weight losses with current anti-obesity agents appear modest but may be of clinical benefit, and 2. better studies designed to examine mortality and cardiovascular morbidity are required to fully evaluate any potential benefit of such agents.

Authors' conclusions: 

Orlistat, sibutramine and rimonabant have been studied in trials of one year or longer. Internal validity of studies was limited by high attrition rates. All three antiobesity agents are modestly effective in reducing weight and have differing effects on cardiovascular risk and adverse effects profiles. Longer and more methodologically rigorous studies of anti-obesity drugs that are powered to examine endpoints such as mortality and cardiovascular morbidity are required.

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Obesity is a highly and increasingly prevalent chronic condition for which drugs are commonly prescribed to improve health.


To assess the long-term effects of approved anti-obesity medications in clinical trials of at least one-year duration.

Search strategy: 

MEDLINE, EMBASE, The Cochrane Library, the Current Science Meta-register of Controlled Trials and reference lists were searched. Drug manufacturers and two obesity experts were contacted.

Selection criteria: 

Double-blind, randomised placebo-controlled trials of approved anti-obesity agents that 1) included patients over 18 years, 2) used an intention-to-treat analysis, and 3) had follow-up of one year or more. Both weight loss and weight maintenance trials were included. Abstracts, pseudo-randomised trials, head-to-head trials and open-label studies were excluded.

Data collection and analysis: 

Two reviewers independently assessed all potentially relevant reports for inclusion and methodological quality. Data were extracted using double data entry. The primary outcome measure was weight loss.

Main results: 

Sixteen orlistat (n = 10,631), 10 sibutramine (n = 2623) and four rimonabant trials (n = 6365) met inclusion criteria. Attrition rates averaged 30% to 40%. Compared to placebo, orlistat reduced weight by 2.9 kg (95% confidence interval (CI) 2.5 to 3.2 kg), sibutramine by 4.2 kg (95% CI 3.6 to 4.7 kg), and rimonabant by 4.7 kg (95% CI 4.1 to 5.3 kg). Patients on active drug therapy were significantly more likely to achieve 5% and 10% weight loss thresholds. Placebo-controlled weight losses were consistently lower in patients with diabetes. Orlistat reduced diabetes incidence, improved total cholesterol, LDL-cholesterol, blood pressure, and glycaemic control in patients with diabetes but increased rates of gastrointestinal side effects and slightly lowered HDL levels. Sibutramine improved HDL and triglyceride levels but raised blood pressure and pulse rate. Rimonabant improved HDL-cholesterol, triglyceride and blood pressure levels and glycaemic control in patients with diabetes but increased the risk of mood disorders.