Trihexyphenidyl is an antispasmodic drug used as an adjunct drug in the management of parkinsonism and as a treatment for extrapyramidal symptoms caused by drugs affecting the central nervous system (CNS). Trihexyphenidyl is a non-selective muscarinic acetylcholine receptor antagonist but binds with higher affinity to the M1 subtype. In vivo studies have shown that trihexyphenidyl demonstrates higher affinity for central muscarinic receptors located in the cerebral cortex and lower affinity for those located peripherally. Other studies suggest that trihexyphenidyl may modify nicotinic acetylcholine receptor neurotransmission, leading indirectly to enhanced dopamine release in the striatum. Although the anticholinergic has proven to be useful in the treatment of symptoms associated with Parkinson’s disease or other movement disorders, its mechanism of action has yet to be fully elucidated. The precise mechanism of action of trihexyphenidyl remains inadequately comprehended; it appears to act on the parasympathetic nervous system by inhibiting efferent impulses directly. Structures innervated by the parasympathetic system, such as the salivary glands, eyes, and smooth muscles (directly and indirectly), are affected, even at smaller doses. Possible side effects of using Trihexyphenidyl may include dry mouth, constipation, nausea, and vomiting. Trihexyphenidyl is administered as an oral tablet.

Trihexyphenidyl Pathway References