The pharmacologic treatment of Parkinsonism is severely limited in effectiveness since at best only 20% to 30% reduction of symptoms can be achieved. Accordingly, the search continues for new medicines or modifications of present medicines which will give better control of symptoms with fewer side-effects. Biperiden (Akineton), 2-piperidino-1-phenyl-1-bicycloheptemyl-propanol, is such an analogue of trihexyphenidyl (Artane), whose structural relationships are shown in the figure.
Haas and Klavehn1 in animal experiments found that biperiden has 4 times the antinicotinic action of atropine, caramiphen (Panparnit), or trihexyphenidyl. Such antinicotinic action in animals has characterized synthetic drugs which proved to be effective against Parkinsonism. Biperiden's peripheral visceral anticholinergic action was greater than that of trihexyphenidyl, equal to that of papaverine and less than that of atropine. Its midriatic, antisialagogic, and constipative effects equalled those of trihexyphenidyl.
Clinical trials of biperiden in Parkinsonism at European clinics2-8 has suggested considerable improvement in rigidity, tremor,