title: Effect of anticholinergic drugs on gastro-intestinal absorption of L-dopa in rats and in man.
abstract: Plasma L-DOPA levels in rats receiving L-DOPA by the oral route were decreased by the concomitant administration of trihexyphenidyl. Following systemic L-DOPA administration no differences were observed between control and trihexyphenidyl-treated rats. Effects similar to those of trihexyphenidyl were observed with atropine. These results indicate that trihexyphenidyl decreases L-DOPA gastrointestinal absorption probably by delaying gastric emptying. The presence in humans of this interaction between the two antiparkinsonian drugs was suggested by similar findings made either in a group of normal volunteers or in a group of parkinsonian patients. These observations suggest that at the clinical level in selected cases the concomitant administration of trihexyphenidyl to patients receiving L-DOPA may decrease the therapeutic efficacy of L-DOPA by reducing its gastrointestinal absorption.
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000818:Animals; D001285:Atropine / Q000008:administration & dosage / Q000494:pharmacology; D004064:Digestive System / Q000378:metabolism*; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007274:Injections, Intraperitoneal; D007408:Intestinal Absorption / Q000187:drug effects*; D007980:Levodopa / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010276:Parasympatholytics / Q000494:pharmacology*; D010300:Parkinson Disease / Q000378:metabolism; D051381:Rats; D013997:Time Factors; D014282:Trihexyphenidyl / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D010276:Parasympatholytics; D007980:Levodopa; D014282:Trihexyphenidyl; D001285:Atropine