[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/) › Cyclizine

# Cyclizine

## H1 antihistamines?

H1 antihistamines

A piperazine antihistamine anti-sickness medicine for nausea, vomiting, motion sickness and vertigo; on the WHO essential list.

Updated Nov 1, 2026

## Quick facts

**Group**
[H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/)

**Target**
Histamine H1 receptor

**Used for**
Nausea and vomiting · Motion sickness · Vertigo

**Key effects**
Drowsiness · Dry mouth · Blurred vision

**Monitor**
Nausea and vomiting control · Sedation

**ATC**
R06AE03

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◎**Histamine H1 receptor**Cyclizine

ⓘ The figure shows doxepin, a tricyclic first-generation H1 blocker, in the human H1 receptor; cyclizine is thought to act at the same receptor.

**Target in 3D:** Histamine H1 receptor. PDB structure 3RZE (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/3RZE) · Drag to rotate · pinch to zoom

Cyclizine is a first-generation H1 antihistamine with antimuscarinic action. It blocks histamine and acetylcholine signalling in the vestibular pathways and the vomiting centre, reducing nausea from motion, vertigo, surgery, opioids and some treatments. It causes drowsiness and anticholinergic effects such as dry mouth and blurred vision.

- Cyclizine blocks H1 and muscarinic receptors
- Vestibular signals to the brainstem are reduced
- The vomiting centre is less stimulated
- Nausea, vomiting and dizziness ease

## Indications

- Nausea and vomiting, including after surgery or from opioids
- Motion sickness
- Vertigo, including Ménière's disease [Ménière disease →](https://durgical.com/en/conditions/meniere-disease/)
- Nausea and vomiting of pregnancy [Hyperemesis gravidarum →](https://durgical.com/en/conditions/hyperemesis-gravidarum/)

## Adverse effects

### Common

- Drowsiness
- Dry mouth
- Blurred vision
- Constipation or diarrhoea
- Headache

### Serious (rare, important)

- Heart rhythm problems: a very fast or slow heartbeat, palpitations
- Muscle twitches, spasms or seizures
- Serious allergic reaction

## Contraindications

- Hypersensitivity to cyclizine
- Caution in severe heart failure, glaucoma and prostate enlargement

## Key interactions

**Alcohol, benzodiazepines, opioids and other CNS depressants**
Additive sedation and slowed breathing

**Other anticholinergic drugs (tricyclic antidepressants, oxybutynin, antipsychotics)**
Additive dry mouth, urinary retention, constipation and confusion

## What is monitored

- Nausea and vomiting control
- Sedation
- Heart rate and rhythm

## Administration and safety

- Tablets by mouth; an injection is used in hospital
- For motion sickness it is taken before travel

## Pregnancy and breastfeeding

Cyclizine can be used in pregnancy when needed, including for morning sickness; the clinician weighs risks and benefits.

## Nursing care

- Assess nausea and vomiting before and after doses
- Teach not to drive or operate machinery until the effect is known, and to avoid alcohol
- Ask the patient to report palpitations, twitching or a rash

## Pharmacokinetics

**Absorption**
Oral; also intramuscular or intravenous

**Metabolism**
Liver

**Onset and duration**
Within about an hour by mouth

## Memory aid

CYCLizine: for the CYCLe of motion, vertigo and vomiting.

## Test yourself

Think of the answer, then tap the question to see it.

## Which receptors does cyclizine block to reduce nausea?

Histamine H1 and muscarinic receptors.

## In which two situations is cyclizine used?

Motion sickness and nausea after surgery (also vertigo and pregnancy sickness).

## Why should a patient on cyclizine avoid driving if drowsy?

Cyclizine, a first-generation antihistamine, causes drowsiness and blurred vision.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/cyclizine/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 3

- [Meclozine](https://durgical.com/en/pharmacology/meclozine/)
- [Promethazine](https://durgical.com/en/pharmacology/promethazine/)
- [Diphenhydramine](https://durgical.com/en/pharmacology/diphenhydramine/)

## Related conditions 2

- [Ménière disease](https://durgical.com/en/conditions/meniere-disease/)
- [Hyperemesis gravidarum](https://durgical.com/en/conditions/hyperemesis-gravidarum/)

[← Back to the class: H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Cyclizine: an anti-sickness medicine - NHS](https://www.nhs.uk/medicines/cyclizine/) (NHS, 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=R06AE03) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/?query=cyclizine) (World Health Organization, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/cyclizine/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/cyclizine/