[Toxicity and tolerance of tryptophan and its metabolites]

For the therapeutic use of tryptophan it is necessary to know its toxicity and pharmacological effects; but very few data are reported in literature on these aspects. On the other hand there are many researches on tryptophan metabolism after a load test and related side effects. From these data it appears that a tryptophan dose of 100 mg/Kg body weight per os is usually well tolerated with exception of some short and slight gastric troubles (vomit, etc.). The lack of references to repeated and long lasting administrations (chronic toxicity) and of a therapeutic index must be filled. Side effects due to a single dose of 5.OH-tryptophan, e.g. head twitches, resemble those due to serotonine. With regard to the most important metabolites of the kynurenine pathway, the available data have been obtained with kynurenine and especially with xanthurenic acid. These compounds have a low toxicity and do not appear to have important pharmacological properties. However, systematic researches are necessary before using these compounds either in load tests or for therapy in man.