Pharmacologic options for the treatment of obesity

Abstract

Past and current drug therapies for weight loss are discussed. More than 50% of Americans can be categorized as overweight or obese. Obesity is associated with increased mortality and with comorbidities such as hypertension, hyperglycemia, dyslipidemia, coronary artery disease, and certain cancers. According to guidelines for identification, evaluation, and treatment of obesity, patients with a body mass index (BMI) of ≥30 kg/m2 should attempt to lose weight. Patients with a BMI of ≥25 kg/m2 plus two or more risk factors or patients with an excessive waist circumference plus two or more risk factors should also attempt to lose weight. The initial goal is a 10% weight reduction in six months achieved through lifestyle changes. If lifestyle changes alone are not effective, then drug therapy may be indicated. Pharmacotherapeutic options for obesity have decreased over the past few years. Fenfluramine, dexfenfluramine, and phenylpropanolamine have been withdrawn because of severe adverse effects, leaving only sympathomimetics, sibutramine, and orlistat as anorectics with FDA-approved labeling. Phentermine has been shown to cause a 5-15% weight loss if given daily or intermittently. Compared with sibutramine and orlistat, phentermine is cheaper, and specific formulations allow once-daily administration. However, phentermine is indicated only for short-term treatment, and tolerance often develops. Common adverse effects associated with phentermine are dry mouth, insomnia, increased blood pressure, and constipation. Sibutramine increases norepinephrine and serotonin levels in the CNS and should not be taken with many antidepressants because of the risk of increased norepinephrine and serotonin levels. Its use is also contraindicated in patients with cardiovascular disease. Orlistat is not systemically absorbed; therefore, it does not cause the systemic adverse effects or drug interactions of phentermine and sibutramine. Orlistat has a cholesterol-lowering effect not seen with other diet medications. However, the three-times-daily administration and frequent gastrointestinal effects limit its use. Sibutramine, phentermine, and orlistat have both positive and negative properties. Choosing among the medications will depend on concurrent disease states and medications, ease of administration, and cost.