Orlistat - A review of its use in the management of obesity

Orlistat is a novel non-systemic treatment for obesity. The drug inhibits lipases in the gastrointestinal tract, preventing the absorption of approximately 30% of dietary fat. Pharmacodynamic and dose-finding studies have established that a 120mg dose of orlistat 3 times daily (with each main meal) is optimal. Controlled studies have established that orlistat 120mg 3 times daily for 1 year, in conjunction with a hypocaloric diet, enables weight reduction of 7.9 to 10.2% in obese non-diabetic individuals. In 1 study the reduction was 6.2% in obese patients with type 2 diabetes. Orlistat 120mg 3 times daily was significantly more effective than placebo (also given in conjunction with a hypocaloric diet) in these studies. The drug was also significantly more effective than placebo in 2-year randomised double-blind studies involving >2000 patients. During the second year of treatment, when patients were switched from a hypocaloric diet to a eucaloric diet, orlistat recipients regained significantly less weight than placebo recipients. Orlistat appears to improve lipid profiles in non-diabetic obese patients, reducing levels of total cholesterol and low density lipoprotein cholesterol. In a study of patients with obesity associated with type 2 diabetes, patients treated with orlistat lost more weight and had improved serum lipid profiles compared with placebo recipients. In addition, orlistat-treated patients achieved significant improvements in glycaemic control, enabling dosages of antidiabetic drugs to be reduced. Long term (1 to 2 years) tolerability data from 2038 patients in placebo controlled trials revealed that the drug was generally well tolerated. The most commonly reported adverse events were related to decreased fat absorption and included oily faecal spotting, flatus with discharge, faecal urgency and oily stool. Systemic adverse events attributable to orlistat were negligible. Conclusion: Orlistat in conjunction with a hypocaloric diet has been shown to induce clinically significant weight loss in keeping with current guidelines for the management of obesity. This, together with its acceptable tolerability profile and lack of systemic adverse events, make it an attractive option in the treatment of obesity. The drug may have a positive effect on obesity-associated cardiovascular risk factors and type 2 diabetes.