title: Tryptophan nicotinic-acid metabolism during levodopa treatment of parkinsonism.
mesh_terms: D004295:Dihydroxyphenylalanine / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009539:Nicotinic Acids / Q000378:metabolism*; D010300:Parkinson Disease / Q000188:drug therapy / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D009539:Nicotinic Acids; D004295:Dihydroxyphenylalanine; D014364:Tryptophan