NCIt definition : The hydrochloride salt form of trihexyphenidyl, a synthetic, substituted piperidine
with parasympatholytic activity used mostly in Parkinson's disease. Trihexyphenidyl
hydrochloride antagonizes activities of acetylcholine via muscarinic receptors. This
balances the cholinergic and dopaminergic activity in the basal ganglia leading to
an improvement of classic Parkinson symptoms such as rigidity and tremor. In addition,
trihexyphenidyl hydrochloride exerts a direct antispasmodic effect on smooth muscle.;