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Cyclizine: Wikis


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Systematic (IUPAC) name
CAS number 82-92-8
ATC code R06AE03
PubChem 6726
DrugBank APRD00061
ChemSpider 6470
Chemical data
Formula C 18H22N2  
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) OTC (NL)
Routes Oral, IM, IV, insufflation
 Yes check.svgY(what is this?)  (verify)

Cyclizine is an antihistamine drug used to treat nausea, vomiting and dizziness associated with motion sickness, vertigo and post-operatively following administration of general anaesthesia and opioids. It is abused as an opiate/opioid-enhancing antihistamine booster and separately for its anticholinergic effects[1].



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.


Its antimuscarinic action warrants caution in patients with prostatic hypertrophy, urinary retention, or 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. Its main off-label use is as an opioid/opiate potentiator, commonly preferred highly to other anti-histamines (most commonly used as opioid boosters: tripelennamine, hydroxyzine, meclizine, doxylamine, diphenhydramine, etc.). The drug Diconal is the opioid Dipipanone and Cyclizine combined for IV use (discontinued in the U.S. for its high abuse potential). Dipipanone's closest relative is methadone. Those using methadone recreationally combine cyclizine with their methadone dose, a combination that is known to produce strong psychoactive effects[2]. It is also sold in combination with another opioid dipipanone under the brand name Diconal.[3] Intravenous cyclizine produces the strongest effects, although it can also be taken orally to achieve a more euphoric high.

Side effects

Common (over 10%) - Drowsiness, xerostomia (dry mouth)

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

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


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


  1. ^ Bassett KE, Schunk JE, Crouch BI. Cyclizine Abuse by Teenagers in Utah. American Journal of Emergency Medicine. 1996; 14, 5
  2. ^ Cyclizine Abuse among a Group of Opiate Dependents Receiving Methadone, Addiction 84 (8), 929–934
  3. ^ Diconal Tablets by Amdipharm. Electronic Medicines Compendium.


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