Body weight loss with phentermine alone versus phentermine and fenfluramine with very-low-calorie diet in an outpatient obesity management program: A retrospective study

Background: Obesity, which is epidemic in the United States, is associated with increased morbidity and mortality. The combination of diet, exercise, and a behavior-modification program often does not result in ideal body weight. Objective: The aim of this study was to determine the efficacy of phentermine (Phen) alone compared with phentermine plus fenfluramine (Phen-Fen), when used in combination with a very-low-calorie diet (VLCD) for weight loss in an outpatient obesity center. Methods: We analyzed data collected at the UCLA outpatient University Obesity Center between 1993 and 1999. Data for patients who attended the center for at least 12 weeks and at least 4 visits, who were taking Phen or Phen-Fen, and whose body mass index (BMI) was ≥30 kg/m ² were included in this retrospective study. Results: During the study period, 3200 visits were recorded. Of 1133 potential participants, 446 patients were included in the analysis (309 women, 137 men; mean [SD] age, 46.7 [11.4] years; mean [SEM] body weight, 109.6 [26.7] kg; mean [SEM] BMI, 38.0 [7.6] kg/m²). Of these, 128 women and 60 men (mean [SEM] body weight at baseline, 103.4 [24.0] kg and 124.9 [28.2] kg, respectively) received Phen alone; 181 women and 77 men (mean [SEM] body weight at baseline, 102.5 [21.4] kg and 124.9 [30.2] kg, respectively) received Phen-Fen. No statistically significant differences were found between the Phen and Phen-Fen groups in mean age, body weight, or BMI for women or men at baseline. No significant differences in the time of weight loss were found when a VLCD was used with Phen alone compared with the Phen-Fen combination for either sex even at 12 weeks. For women, the mean total body weight loss was 7.4% in the Phen group and 8.7% in the Phen-Fen group, but these differences were not significant. For men, the mean total body weight loss was 7.8% in the Phen group and 8.2% in the Phen-Fen group, but these differences were not significant. No significant differences in BMI, severe adverse events, or dropout rate were found between the 2 treatment groups for men or women. Conclusions: This outpatient study did not detect any significant difference between adjunctive uses of Phen compared with Phen-Fen pharmacotherapy when used with VLCD over 12 weeks. Phen can be used to achieve significant weight loss when combined with VLCD. The tolerability and positive physical response further suggest that Phen is a valuable medication for obesity management in the outpatient setting.