Combination phentermine and topiramate extended release in the management of obesity

Losing ≥ 5% of initial weight improves quality of life and risk factors for cardiovascular disease (CVD) in obese individuals. Lifestyle modification, the cornerstone of weight reduction, may be complemented by pharmacotherapy. In 2012, the FDA approved the combination of phentermine and topiramate extended release (ER) for chronic weight management, as an adjunct to lifestyle modification.

This review examines the safety and efficacy of phentermine-topiramate ER, as determined by randomized controlled trials (RCTs). A preliminary study confirmed the benefit of combining the two medications for improving weight loss and reducing adverse effects, as compared to using equivalent-dose monotherapy alone.

Across RCTs, groups prescribed phentermine 15 mg/topiramate ER 92 mg lost an average of 10% of initial weight, ∼ 8% more than placebo and 2% more than phentermine 7.5 mg/topiramate 46 mg. Weight loss reduced the risk of developing type 2 diabetes and improved CVD risk factors. Phentermine-topiramate ER, however, was associated with increased heart rate, the clinical significance of which is being investigated in an FDA-required CVD outcomes study. The medication also must be used with caution in women of child-bearing age because of an increased risk to infants of oral cleft.