The development of aminoalcohols as parasympatholyticstook place in the 1940s. It was soon established, however,that these antispasmodics were equally efficacious inparkinsonism. Several of the drugs in this class of antimuscarinic agentspossess bulky groups in the vicinity of hydroxyl and cyclicamino functional groups. These compounds are similar to theclassic aminoester anticholinergic compounds derived fromatropine. The presence of the alcohol group seems to substituteadequately as a prosthetic group for the carboxyl functionin creating an effective parasympathetic blocking agent. Theaminoester group, per se, is not a necessary adjunct to cholinolyticactivity, provided that other polar groupings, suchas the hydroxyl, can substitute as a prosthetic group for thecarboxyl function. Another structural feature common toall aminoalcohol anticholinergics is the -aminopropanolarrangement, with three carbons intervening between the hydroxyland amino functions. All of the aminoalcohols usedfor paralysis agitans are tertiary amines. Because the desiredlocus of action is central, formation of a quaternary ammoniummoiety destroys the antiparkinsonian properties. Theseaminoalcohols have been quaternized, however, to enhancethe anticholinergic activity to produce an antispasmodic andantisecretory compound, such as tridihexethyl chloride.
