Utilization of Low-Dose Phentermine for Weight Loss Prior to Metabolic and Bariatric Surgery: A Prospective, Randomized, and Placebo-Controlled Trial.

Introduction: Studies examining preoperative weight loss using pharmacotherapy in metabolic and bariatric patients are limited. The objective was to investigate if patients taking a low-dose formulation of phentermine had improved weight loss.

Methods: This study was a randomized, placebo-controlled trial including patients undergoing laparoscopic Roux-en-Y gastric bypass and sleeve gastrectomy. Anthropometric and serological data were collected during the initial consult visit and again during two follow-up visits. Lomaira is a low-dose formulation of phentermine. Patients took 8-mg tablets three times a day for 14 weeks. The primary outcome of this study was weight loss, which was measured as percentage total weight loss (%TWL) and change in body mass index (BMI).

Results: Among 53 participants randomized, 45 (85%) completed the trial. Participants were predominantly female (91%); the mean age was 41 years (SD = 11); and the mean initial BMI was 48.4 kg/m² (SD = 8.2 kg/m²). Average weight loss was 6.2 kg (SD = 6) in the treatment group versus 1.1 kg (SD = 4.54) in the placebo group (p = 0.001). Average % TWL was greater in treatment Group 4.7 ± 4.3 versus placebo Group 1.1 ± 3.6, p = 0.001. Multivariate regression analysis demonstrated that preoperative medication use was significantly associated with greater %TWL (p = 0.004). There was no difference in OR time or post-operative complications between the groups.

Conclusions: Low-dose phentermine is efficacious and safe for preoperative weight loss in patients undergoing metabolic and bariatric surgery.