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Cyclizine
Cyclizine antagonizes human H1 receptors and appears able to inhibit acetylcholine functions1. It is a piperazine-class antihistamine with anticholinergic properties2 and is used to help treat nausea and vomiting, including motion sickness and sickness caused by some inner-ear problems3. Developed in 1947,1 drowsiness has been reported with cyclizine2 and may produce delirium and vivid, realistic hallucinations at high doses, which are reported as uncomfortable. Reported adverse effects include dry mouth, constipation, and blurred vision2; other reported adverse effects include low blood pressure and urinary retention2.
Dosage & Duration
Dosage
Doses are population estimates that vary widely between individuals.
The dosages listed reflect those established for therapeutic applications.
Duration
Subjective Effects
Pharmacology
Pharmacodynamics
Cyclizine is a histamine H1-receptor antagonist with anticholinergic properties4. These actions reduce vestibular signaling and may affect the medullary chemoreceptor trigger zone, contributing to its antiemetic and antivertigo activity. Its precise mechanism in motion sickness is not fully established4, and it may act directly on vestibular pathways as well as the chemoreceptor trigger zone.
Pharmacokinetics
Cyclizine is metabolized to the N-demethylated metabolite norcyclizine.4 After a single oral 50 mg dose in healthy adult volunteers, its plasma elimination half-life was approximately 20 hours4.
Interactions
An unlisted combination is an unknown one, not a safe one. Check a dedicated combination chart before mixing.
Tolerance
Harm Potential
Addiction & Dependence
Psychological
LowSome recreational use has been documented, particularly in combination with methadone to produce psychoactive effects, and for its anticholinergic hallucinogenic properties. However, the experience is reported to be uncomfortable and not enjoyable at high dosages.
Toxicity
Rare liver dysfunction has been reported; liver disease may exacerbate sedative effects, warranting caution in patients with pre-existing hepatic conditions.
Tachycardia and low blood pressure may occur as antimuscarinic effects, typically at higher doses or in susceptible individuals.
Urinary retention may occur as an antimuscarinic effect, particularly in patients with prostatic hypertrophy or pre-existing urinary conditions.
CNS effects including drowsiness, psychomotor impairment, confusion, depression, sleep disturbances, and tremor have been reported; extrapyramidal effects occur rarely.
Visual disturbances including blurred vision and diplopia may occur as antimuscarinic effects; use is contraindicated in angle-closure glaucoma.
Psychosis Risk
At high dosages, cyclizine typically induces delirium and vivid realistic hallucinations due to its anticholinergic properties. Hallucinations are listed as a rare adverse effect at therapeutic doses. Confusion has also been reported rarely.
History & Culture
Discovery and development
Cyclizine was developed by Burroughs Wellcome in 1947.5 It was identified clinically as a potent, long-acting antiemetic, and the company marketed its hydrochloride form in the United States under the name Marezine. A related U.S. patent was assigned to Burroughs Wellcome in 1953.
Legality
International
Over the counter in many countries.
By Country
United StatesLegal (regulated)
SingaporeLegal (regulated)References
Citations
Article Status
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