Pharmacology · Class
Antiparkinson anticholinergics !
Central antimuscarinic drugs for tremor and drug-induced dystonia or parkinsonism. Poorly tolerated by older adults: confusion, retention, constipation.
Updated 2026-11-01
What they are
Trihexyphenidyl, benzatropine and biperiden block muscarinic receptors in the brain. They have modest antiparkinson activity (mostly on tremor and rigidity) and are widely used for acute dystonia and parkinsonism caused by antipsychotics.
Mechanism of action
In the striatum, dopamine and acetylcholine balance each other. When dopamine falls (Parkinson disease or a dopamine-blocking drug), cholinergic interneurons dominate; blocking their muscarinic receptors restores part of the balance.
Target: Muscarinic acetylcholine receptors
Drugs in this class
- BenzatropineA central anticholinergic used for drug-induced dystonia and parkinsonism and for Parkinson tremor. Older adults…Muscarinic acetylcholine receptors (M1 shown)
- TrihexyphenidylA central anticholinergic for parkinsonian tremor and drug-induced extrapyramidal effects. Avoided in older adults and…Muscarinic acetylcholine receptors (M1 shown)
- BiperidenA central anticholinergic on the WHO essential list, given by mouth or injection for parkinsonism and acute dystonia…Muscarinic acetylcholine receptors (M1 shown)
Others in the class
- Prociclidina
- Orfenadrina
- Difenhidramina
Test yourself
Think of the answer, then tap the question to see it.
Why are antiparkinson anticholinergics usually avoided in older adults?
Older people are more sensitive to their central and peripheral effects: confusion, delirium, urinary retention, constipation and falls.
Which antipsychotic movement disorder do anticholinergics not treat?
Tardive dyskinesia, which they may even worsen.
Which eye condition contraindicates them?
Angle-closure glaucoma.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 21 (McGraw Hill, 2023); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 28 (McGraw Hill, 2025); Trihexyphenidyl: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2018); Benztropine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2018).
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Representative model, for educational purposes only.