The effect of fenfluramine on weight loss during restricted dietary regimes.

Fenfluramine therapy 180 mg per day did not increase the rate of weight loss in obese patients either undergoing therapeutic starvation or receiving a 300 kcal diet; neither did the drug alter those biochemical changes associated with these dietary regimes. These results suggest that fenfluramine does not cause weight loss in the obese patient by a major metabolic action but by its effect on appetite. However, there were significant differences in the ratios of fenfluramine to norfenfluramine in the plasma and urine of patients on each dietary regimen.