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Systematic (IUPAC) name
Clinical data
Routes of
Oral, IM, IV, insufflation
Legal status
Legal status
  • P/POM (UK) OTC (NL)
Pharmacokinetic data
Metabolism N-demethylated to inactive norcyclizine
Biological half-life 20 hours
CAS Number 82-92-8
ATC code R06AE03 (WHO)
PubChem CID 6726
DrugBank APRD00061
ChemSpider 6470
Chemical data
Formula C18H22N2
Molar mass 266.381 g/mol[[Script error: No such module "String".]]
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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 also used recreationally 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, often highly preferred to other anti-histamines (most commonly used orally, or intravenously in cyclizine's case, as opioid boosters: tripelennamine, hydroxyzine, meclizine, doxylamine, diphenhydramine, etc.). Intravenous cyclizine produces the strongest effects, although it can also be taken orally to achieve a more euphoric high.[citation needed] Those using methadone recreationally combine cyclizine with their methadone dose, a combination that is known to produce strong psychoactive effects.[2]

The drug Diconal is a combination of cyclizine with the closely-related methadone derivative opioid dipipanone, for I.V. use.[3] Diconal has been discontinued in the US for its high abuse potential; however, some small pharmacies carry cyclizine HCl 50mg tablets sold as "Marezine". While containing binders and mildly thickening agents, they don't "gel", so can still be made into a liquid solution possible to inject.[citation needed] The pills contain several binders/fillers, possibly due to the previous I.V. abuse of cyclizine, which may be why Marezine is rare in the US, as well as expensive, averaging around $1.00 per pill in boxes of 12.[citation needed]

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). Cyclizine HCl 25 mg is marketed as Bonine for Kids in the US.[4]

See also


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it:Ciclizina pl:Cyklizyna fi:Syklitsiini

  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.
  4. Bonine for Kids