The new weight-loss drugs, lorcaserin and phentermine-topiramate: slim pickings?

Abstract

In 2012, the US Food and Drug Administration approved 2 drugs for long-term weight loss: lorcaserin hydrochloride (Belviq; Eisai Inc) and phentermine-topiramate (Qysmia; Vivus Inc). The approvals were based on 1-year trials showing that on top of recommendations to follow a calorie-restricted diet and to increase exercise, patients randomized to either drug lost more weight than patients randomized to placebo (3% [95% CI, 3%-4%] more weight lost with lorcaserin; 7% [95% CI, 3%-4%] more with phentermine /topiramate). The drugs have been associated with serious harms: Both drugs' labels include warnings about memory, attention, or language problems and depression; for lorcaserin, the label also warns of valvular heart disease and euphoria; and for phentermine-topiramate, the label warns of metabolic acidosis, increased heart rate, anxiety, insomnia, and elevated creatinine levels. Neither medication is marketed in Europe because of safety concerns. The manufacturer withdrew its application for lorcaserin in Europe after the European Medicines Agency (EMA) said approval was unlikely, and the EMA rejected phentermine-topiramate. In the United States, the required postmarketing safety trials are behind schedule. Until there is more convincing evidence about the cardiovascular safety of these drugs, physicians and patients should approach them cautiously. Patients who do not lose at least 5% of their body weight within 12 weeks of starting to take either drug should stop taking it, as stated in the prescribing information.