Qualitative and quantitative effects of fenfluramine and tiflorex on food consumption in trained rats offered dietary choices.

The qualitative and quantitative anorectic effects of intraperitoneally-administered fenfluramine and tiflorex were studied in male rats trained during 10 d to a reversed dark/light cycle ('night' 1100-2300 h), and to a food choice (of either a protein-rich or protein-poor meal, or of a carbohydrate-rich or carbohydrate-poor meal) available only during the first 4 h of the dark cycle. On the first day of drug treatment (2.5 mg/kg or 5.0 mg/kg i.p., administered 0.5 h before the end of the light cycle) both fenfluramine and tiflorex provoked a dose-dependent reduction in the consumption of the protein-rich diet, and a reduction in the consumption of the protein-poor diet. In the carbohydrate study, on the first day of drug treatment, there was a dose-related reduction in the consumption of the carbohydrate-rich regime, and marked reduction by both drugs of consumption of the carbohydrate-poor regime (except in the case of the lower dose of fenfluramine, 2.5 mg/kg). There was generally a rapid development of tolerance to the anorectic effects of the anti-obesity drugs, although this was delayed somewhat in the case of tiflorex. These results suggest that drugs like fenfluramine and tiflorex, which enhance central serotoninergic transmission, reduce caloric intake whether the calories are presented as protein or carbohydrate, compatible with the anti-obesity actions of these agents in omnivorous man.