Species-dependent effects of fenfluramine on the central nervous system

The cortical effects of fenfluramine and a metabolite, norfenfluramine, were studied in rabbits and cats. The parent compound produced slow waves in the e.e.g. which were compatible with sedation in cats. Norfenfluramine also produced slow waves and apparent sedation in cats, but neither compound produced marked changes in the cortical waves of rabbits. When cortical waves in both species were slowed with pentobarbitone, fenfluramine increased the frequency of the waves in rabbits but did not alter the frequency in cats. Both fenfluramine and the metabolite blocked cortical after-discharges in both species. There is no apparent explanation for the differences in the action of the two drugs in the two species.