Successful treatment of obesity requires a multidisciplinary approach including diet, exercise and behavioral modification. As lifestyle changes are not sufficient for some patients, pharmacologic therapies should be considered as adjuncts to lifestyle interventions. In this article, we review clinical indications, mechanisms of action, dosing/administration, side effects, drug interactions and contraindications for the six most widely prescribed obesity medications. We also summarize the efficacy data from phase 3 trials which led to drug approval. As multiple agents are sometimes required for clinically significant weight loss, the future of obesity medicine will likely involve combinations of agents in addition to behavioral counseling.