Tryptophan/nicotinic acid pathway during levodopa treatment of Parkinsonism.

The behaviour of some urinary metabolites of tryptophan/nicotinic acid pathway was studied in 7 patients with Parkinson's disease during a 24-day period of levodopa treatment. Corresponding to the appearance of side-effects (agitation, anorexia, dysphagia, glossitis, abdominal pains) in 5 patients there was an increase in urinary Ky, AA, AAG, o-AHA, and 3-HK, while 3-HAA excretion fell. Since no other drugs were given, it was presumed that this effect was due to levodopa administration.