Randomized controlled trial to investigate the effects of a newly developed formulation of phentermine diffuse-controlled release for obesity

Aim: To evaluate the efficacy and safety of a newly developed formulation of phentermine diffuse-controlled release (DCR) in patients with obesity. Methods: This was a randomized, double-blind, placebo-controlled trial of 12 weeks of treatment with phentermine DCR 30 mg (n = 37) or placebo (n = 37), administered once daily in patients with obesity with controlled diabetes, hypertension or dyslipidaemia. The efficacy was evaluated by changes in body weight and waist circumference from baseline at 12 weeks and also changes in metabolic parameters, including lipid profiles and blood pressure. Results: The participants in the phentermine DCR group showed significant reductions in body weight (-8.1 ± 3.9 vs. -1.7 ± 2.9 kg, p < 0.001) and waist circumference (7.2 ± 0.5 vs. 2.1 ± 0.6 cm, p < 0.001) compared with those in the placebo group. Weight reductions of 5% or greater from the baseline (95.8 vs. 20.8%, p < 0.001) and 10% or more (62.5 vs. 4.7%, p < 0.001) were achieved in the DCR phentermine group and placebo group, respectively. Total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels were significantly improved in the phentermine DCR group. However, there were no significant differences in systolic and diastolic blood pressure between the groups. Dry mouth and insomnia were the most common adverse events, but these were mild to moderate and transient. Conclusions: Short-term phentermine DCR treatment resulted in significant reduction in weight and improvement of metabolic parameters, including waist circumference and some lipid profiles, without clinically severe adverse events. Further study is needed to show long-term efficacy and safety of phentermine DCR in Korean patients with obesity.