Modulation of the thermic effect of food by fenfluramine.

The thermogenic effect of fenfluramine was examined in rats following either fasting or the ingestion of a large meal. Fenfluramine did not produce a thermogenic effect in the fasting animal, but significantly potentiated the thermogenic effect of the meal. Furthermore, fenfluramine was found to produce a significant thermogenic effect when accompanied with a glucose meal, but not with one consisting of fat. These data demonstrate the importance of drug and nutrient interactions in the analysis of thermogenesis and suggest that substrate cycling may play a role in the thermogenic effect of fenfluramine.