The effect of withdrawal and re-introduction of dexfenfluramine in the treatment of obesity.

In this study 25 patients, who had completed the INDEX trial (Guy-Grand et al. Lancet 1989; 2: 1142-1145) were reexamined 2 months after withdrawal of the study medication. The patients then in an open trial received dexfenfluramine (dF) for 6 months. The observed weight gain after withdrawal of study medication was higher in patients treated beforehand with dF (2.6 +/- 1.2 kg) than in patients who had received placebo (0.8 +/- 1.0 kg). In the open dF trial rate of weight loss was lower than it had initially been in the patients receiving dF from the outset of the INDEX trial (13.1 +/- 4.6 kg within 6 months). In the previous dF treated patients weight loss after re-introduction of dF was 3.7 +/- 2.7 kg. The previous placebo-treated patients, now receiving dF for the first time, lost 4.8 +/- 1.1 kg. Thus, after withdrawal of dF, patients experience weight gain, but after re-introduction of dF, renewed weight loss is achieved. However, the rate of weight loss declines with time.