The influence of tryptophan and parachlorophenylalanine on the sexual activity in man.

The effects on the sexual tone of parachlorophenylalanine, a selective inhibtor of 5-hydroxytryptamine synthesis, testosterone and placebo were evaluated in patients complaining of migraine-headache and sexual deficiency. The combined treatment with parachlorophenylalanine and testosterone significantly increases the sexual stimulus more than parachlorophenylalanine, testosterone and placebo, when given on their own. Conversely subjects with normal or excessive sexual activity, reported a decrease of sexual tone, during chronic treatment with tryptophan. The hypothesis of an implication of brain 5-HT in the mechanism of psychogenic sexual deficiency and the possibility of a therapeutic approach with drugs able to interfere with 5-HT turnover are discussed.