The New Weight-Loss Drugs, Lorcaserin and Phentermine-Topiramate: Slim Pickings?


The US Food and Drug Administration recently approved two drugs for weight loss. Both lorcaserin hydrochloride (Belviq; Eisai Inc.) and phentermine-topiramate (Qysmia; Vivus Inc.) demonstrated greater weight loss over a 1-year period compared to control groups. In addition to the medications, patients followed a low-calorie diet and performed regular exercise. Lorcaserin is a selective 5-HT2C receptor agonist. It is hypothesized that lorcaserin targets receptors in the brain that generate a sense of satiety. Phentermine-topiramate is a combination drug. Phentermine is a sympathomimetic agent, which is an appetite suppressant. Topiramate is an antiepileptic drug, which promotes weight loss; currently, the mechanism of action is not clear.

Both drugs have possible serious adverse effects. Labeling for both lorcaserin and phentermine-topiramate warn of problems with memory, attention, and/or language as well as depression. Additional warnings for lorcaserin include valvular abnormalities, and for phentermine-topiramate, the label warns of metabolic acidosis, increased heart rate, anxiety, insomnia, and elevated creatinine levels. The most common adverse effects for phentermine-topiramate were paresthesias and dry mouth, and for lorcaserin, headache and dizziness. These concerns have led to neither medications being marked in Europe. Currently, the United States requires post-marketing safety trials; however, these trials are behind schedule. It is recommended that for patients who do not lose 5% or more of their body weight in 12 weeks, these drugs should be discontinued.

The authors expressed concerns that these drugs were approved prior to having adequate data on long-term safety including any adverse cardiovascular effects. The authors state that adults who are overweight or obese need effective strategies to lose weight; however, safety of any interventions needs to be considered. Physicians and patients should approach these medications with caution.


The statement outlines two new medications, which are approved for the treatment of obesity. However, as the authors state, concerns regarding the safety of these medications exist. These medications should be used with caution and the pros and cons of these medications should be discussed with patients who are interested in using them.

Keywords: Depression, Sleep Initiation and Maintenance Disorders, Phentermine, Paresthesia, Heart Rate, Headache, Caloric Restriction, Dizziness, United States Food and Drug Administration, Attention, Obesity

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