Cyclizine, sold under a number of brand names, is a medication used to treat and prevent nausea, vomiting and dizziness due to motion sickness or vertigo.

[3][4] Common side effects include sleepiness, dry mouth, constipation, and trouble with vision.

[6] Primary uses include nausea, vomiting and dizziness associated with motion sickness, vertigo and post-operatively following administration of general anesthesia and opioids.

[12] Its antimuscarinic action warrants caution in patients with prostatic hypertrophy, urinary retention, or angle-closure glaucoma.

Uncommon (1% to 10%) — Headache, psychomotor impairment, dermatitis, and antimuscarinic effects such as diplopia (double vision), tachycardia, constipation, urinary retention and gastro-intestinal disturbances.

[10] Cyclizine may be prepared by the Eschweiler–Clarke methylation of diphenylmethylpiperazine or by reaction of benzhydryl bromide with 1-methylpiperazine in acetonitrile to form the hydrobromide salt of the drug.

Cyclizine was developed in the American division of pharmacy company Burroughs Wellcome (today GlaxoSmithKline) during a research study involving many drugs of the antihistamine group.

[13][14] The substance received more credit when NASA chose it as a space antiemetic for the first crewed Moon flight.