[Clinical pharmacology of anticholinergic antiparkinson agents. A review with emphasis on acute toxicity].

Today, anticholinergic antiparkinsonian drugs are primarily used to ameliorate extrapyramidal side-effects induced by neuroleptic agents. Orphenadrine dominates quantitatively among these drugs in Norway, presumably because it is assumed to carry a lower risk of abuse. There are numerous reports of deaths following orphenadrine overdoses. Orphenadrine has complex pharmacokinetic properties and a narrow therapeutic index. After an overdose, it confers toxic effects of rapid onset to several organ systems. No specific and effective therapy for orphenadrine intoxication has been established. For the two other drugs in this class which are marketed in Norway, biperiden and benztropine, toxicity is mainly connected to their anticholinergic properties. Notably, no reports of lethalities after overdoses of biperiden seem to be available. A small number of accounts of deaths following benztropine intoxication have been published. Neither of these two agents, and benztropine in particular, has been subjected to comprehensive pharmacokinetic evaluations. The relatively extensive use of orphenadrine should be discouraged.