Trihexyphenidyl

Trihexyphenidyl is a medication in the antimuscarinic class used to treat Parkinsonism and drug-induced extrapyramidal symptoms. It is also employed to manage dystonia and tremor in some adults, and is sometimes used as an adjunct to levodopa therapy to help control tremor and rigidity.

Pharmacology and mechanism of action: Trihexyphenidyl acts as a competitive antagonist of muscarinic acetylcholine receptors, predominantly M1. By reducing cholinergic activity in the striatum, it helps rebalance the disrupted dopaminergic-cholinergic system in Parkinsonian syndromes. It is lipophilic enough to cross the blood-brain barrier, producing central and peripheral anticholinergic effects.

indications and usage: It is indicated for idiopathic Parkinson’s disease, parkinsonism due to medications (drug-induced), and dystonic syndromes. It may be used as an adjunct to dopaminergic therapy to lessen tremor and rigidity when other treatments are insufficient. It does not slow disease progression and is not a substitute for disease-modifying therapy.

Administration and dosage: Trihexyphenidyl is given orally as tablets or solution. Starting doses are typically 1 mg one to three times daily, with gradual increases based on response and tolerability. Common total daily doses range from 2 to 5 mg, though some adults may require higher amounts up to around 15 mg per day. Dose adjustments are generally made cautiously, especially in older patients.

adverse effects and precautions: Anticholinergic adverse effects are common and can include dry mouth, constipation, blurred vision, urinary retention, dizziness, confusion, and cognitive impairment, particularly in older individuals. Additional risks include tachycardia, photophobia, and, in patients with glaucoma, urinary retention. Contraindications include narrow-angle glaucoma, myasthenia gravis, urinary or gastrointestinal obstruction, and hypersensitivity. Caution is advised when combining with other anticholinergic drugs or CNS depressants. brand names include Artane.