Introduction: Controlled-release phentermine/topiramate (PHEN/TPM CR) is being investigated as a weight loss therapy. It is given as a single daily morning dose, and it contains 15 mg PHEN (immediate release) and 92 mg TPM (controlled-release). While the individual components have published dose-related efficacy, tolerability, and adverse event data, the combination did not have that, so this study was done.
Methods: This was a 56-week randomized, double-blind, parallel-group controlled trial to evaluate safety and efficacy of PHEN/TPM CR. The 3 arms were: randomized in a 2:1:2 ratio, and they were: placebo (n = 514), PHEN/TPM CT 3.75/23 mg (n = 241), and PHEN/TPM CR 15/92 mg (n = 512). Men and women with class II and class III obesity (BMI ≥ 35 kg/m2) were included. All were also on a reduced-energy meal plan.
Primary endpoints were:
Secondary endpoints were:
Results: The primary analysis was done on patients with at least one post-baseline weight measurement and who had taken at least one dose of their assigned drug/placebo. In that analysis at 56 weeks, the following weight loss percents were seen (p < 0.0001):
Categorical analysis showed that the following portions of patients achieved at least 5% WL (p < 0.0001):
When compared to placebo, the 15/92 group showed significantly greater changes in WC, BP (systolic and diastolic), fasting blood glucose, and lipid measures.
The most common adverse events were: paresthesia, dry mouth, constipation, dysgeusia, and insomnia.
Conclusions: This study showed that PHEN/TPM CT has a dose-dependent beneficial effect on weight and metabolic variables. There is no evidence of serious adverse events.
Commentary by J. Michael Gonzalez-Campoy MD, PhD, FACETo read Dr. Gonzalez-Campoy's commentary on this study, read his introduction.