Lower dosages of phentermine-fenfluramine given in the afternoon: five cases with significant weight loss

Int J Eat Disord. 1999 May;25(4):469-74. doi: 10.1002/(sici)1098-108x(199905)25:4<469::aid-eat13>3.0.co;2-h.


Phentermine and fenfluramine are widely used in the treatment of obesity. Despite the fact that primary pulmonary hypertension and mitral valve insufficiency have been associated with fenfluramine use, many of these patients need medication to achieve weight loss. Small degrees of weight loss have been shown to significantly improve obesity-related medical conditions such as hypertension, hypercholesterolemia, and noninsulin-dependent diabetes mellitus. Current practice is to give phentermine and fenfluramine in the morning and afternoon. Doses for phentermine have ranged from 15 to 37.5 mg and for fenfluramine from 20 to 120 mg per day. We report five cases of severely obese women with medical complications who were treated with phentermine 8 mg twice per day (at 1:00 p.m. and 4:00 p.m.) and fenfluramine 20 mg per day (at 4:00 p.m.). Because many obese patients skip breakfast and eat more in the afternoon and evening, medication was dosed in order to cover these high-risk eating periods. Overall, these patients lost a mean of 22.4% of their initial weight (range 18.6% to 32.8%) over an average of 8.4 months (range 3.5 to 16 months). These cases suggest that short-term weight loss can be achieved with a low dose of fenfluramine when both medications are given in the afternoon to better target the eating patterns of obese subjects.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Circadian Rhythm
  • Dopamine Uptake Inhibitors / therapeutic use*
  • Dose-Response Relationship, Drug
  • Drug Combinations
  • Female
  • Fenfluramine / therapeutic use*
  • Humans
  • Middle Aged
  • Obesity / drug therapy*
  • Phentermine / therapeutic use*
  • Time Factors
  • Weight Loss*


  • Dopamine Uptake Inhibitors
  • Drug Combinations
  • Fenfluramine
  • Phentermine