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Biperiden (marketed as Akineton) is an anticholinergic agent used to treat parkinsonism and the extrapyramidal side effects caused by antipsychotic drugs. Compared with older nonselective anticholinergics it shows relative selectivity for the M1 muscarinic acetylcholine receptor subtype, a property that has made it a widely used pharmacological probe for dissecting cholinergic contributions to memory, cognition, and antidepressant response in animal and human studies. Experimental work has employed it to model muscarinic cognitive impairment, to examine M1-mediated modulation of reward and cocaine-related behaviors, and to probe brain choline metabolism and functional connectivity in psychosis. Although it is a legitimate prescription medicine, biperiden is a dangerous deliriant at high doses, producing a distressing anticholinergic delirium rather than pleasurable effects.
- Treats Parkinsonism, particularly tremor and rigidity
- Relieves antipsychotic-induced extrapyramidal symptoms and dystonia
- Injectable form treats acute drug-induced dystonic reactions
- Relatively M1-selective muscarinic antagonist used as a research probe
- Dry mouth, blurred vision and constipation
- Urinary retention
- Confusion and memory problems, especially in older adults
- Delirium and hallucinations at high doses
Mechanism
Biperiden is a receptor with relative selectivity for the M1 subtype (the subtype most prominent in the and ). In Parkinsonism and antipsychotic-induced movement disorders, blocking central cholinergic activity helps rebalance the -acetylcholine interplay in the basal ganglia, easing tremor, rigidity and dystonia. Because it readily enters the brain and blocks central muscarinic receptors, high doses cause an anticholinergic delirium; the same M1 blockade that helps movement problems at therapeutic doses drives confusion and hallucinations when overdone, alongside peripheral muscarinic blockade that produces the rest of the toxidrome.
receptor fingerprint
M1 receptorAntagonist
Other subtypes (M2-M5)Antagonist
Safetyrisks and cautions, not medical advice
Biperiden is a serious prescription drug; high doses cause anticholinergic delirium with realistic hallucinations mistaken for reality, confusion and memory loss, plus the toxidrome: blurred vision, dangerous overheating, flushed dry skin, dry mouth, racing heart, urinary retention, seizures and potentially death. Combining it with other anticholinergics, including sedating antihistamines and other deliriants, stacks anticholinergic burden and raises the danger. High anticholinergic burden is associated with greater dementia risk in older people and with long-term use. Not medical advice.
Subjective profileweighing the evidence above
A legitimate prescription drug for Parkinsonian tremor and antipsychotic-induced movement problems, and nothing to experiment with; high doses produce a dangerous anticholinergic delirium with overheating and seizures, and heavy anticholinergic burden tracks with higher dementia risk in older people.
Resources
This entry is here for reference.
Research
- 1988first cited[Delirium syndrome in biperiden poisoning].
- 2019most recentInfluence of muscarinic M1 receptor antagonism on brain choline levels and functional connectiv…
- 1.Selectivity of antimuscarinic compounds for muscarinic receptors of human brain and heart.
- 2.Managing antipsychotic-induced parkinsonism.
- 3.[Delirium syndrome in biperiden poisoning].
- 4.M1 and M2 muscarinic receptor subtypes regulate antidepressant-like effects of the rapidly acting antidepressant scopolamine.
- 5.Performance of conventional pigs and Göttingen miniature pigs in a spatial holeboard task: effects of the putative muscarinic cognition impairer Biperiden.
- 6.Biperiden (M₁ antagonist) impairs the expression of cocaine conditioned place preference but potentiates the expression of cocaine-induced behavioral sensitization.
- 7.Influence of muscarinic M1 receptor antagonism on brain choline levels and functional connectivity in medication-free subjects with psychosis: A placebo controlled, cross-over study.
7 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
What does M1-selective mean for biperiden?
It preferentially blocks the M1 muscarinic subtype, which is common in the brain. That aim helps movement symptoms, but central M1 blockade is also what drives delirium at high doses.
Is biperiden used recreationally?
It is sometimes misused as a deliriant, but there is no pleasant high; high doses cause frightening delirium and a genuinely dangerous toxidrome.
Why is it prescribed alongside antipsychotics?
Antipsychotics can cause parkinsonism and dystonia by blocking dopamine. Biperiden blocks acetylcholine to rebalance that circuit and relieve the movement problems.
Adverse effects
- Dry mouth, blurred vision and constipation
- Urinary retention
- Confusion and memory problems, especially in older adults
- Delirium and hallucinations at high doses