Cyclizine

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Cyclizine
Systematic (IUPAC) name
1-benzhydryl-4-methyl-piperazine
Identifiers
CAS number	82-92-8
ATC code	R06AE03
PubChem	6726
DrugBank	APRD00061
Chemical data
Formula	C18H22N2
Mol. mass	266.381 g/mol
SMILES	eMolecules & PubChem
Pharmacokinetic data
Bioavailability	?
Metabolism	N-demethylated to inactive norcyclizine
Half life	20 hours
Excretion	?
Therapeutic considerations
Pregnancy cat.	A (Au)
Legal status	P/POM (UK)
Routes	Oral, IM, IV

Overview

Cyclizine is an antihistamine drug used to treat nausea, vomiting and dizziness associated with motion sickness, vertigo and post-operative following administration of general anaesthesia and opioids.

Pharmacology

Cyclizine is a piperazine derivative with histamine H₁-receptor antagonist (antihistamine) activity. The precise mechanism of action in inhibiting the symptoms of motion sickness is not well understood. It may have effects directly on the labyrinthine apparatus and on the chemoreceptor trigger zone. Cyclizine exerts a central anticholinergic (antimuscarinic) action.

Contraindications

Its antimuscarinic action warrants caution in patients with prostatic hypertophy, urinary retention, glaucoma. Liver disease exacerbates its sedative effects. It cannot be combined with diclofenac, for example in the same syringe or bag of fluids, as a crystallisation reaction occurs.

Side effects

Common (>10%) - Drowsiness

Uncommon (1% to 10%) - Headache, psychomotor impairment, and antimuscarinic effects such as urinary retention, xerostomia (dry mouth), blurred vision and gastro-intestinal disturbances.

Rare - Hypersensitivity reactions (bronchospasm, angioedema, anaphylaxis, rashes and photosensitivity reactions), extrapyramidal effects, dizziness, confusion, depression, sleep disturbances, tremor, liver dysfunction.

Formulations

As cyclizine hydrochloride 50mg tablets and cyclizine lactate solution for intramuscular or intravenous injection (Brand names: Valoid® in UK and Marezine®, Marzine® and Emoquil® in US)).

References

• British National Formulary 45 March 2003