Cyclizine
Is It Right for You?
A complete guide to Cyclizine — what it treats, how it works, dosages, side effects, and when a clinician may prescribe it following an online consultation.
What Is Cyclizine?
Cyclizine is a first-generation antihistamine with potent antiemetic (anti-nausea and vomiting) and antivertigo properties. It is used to prevent and treat nausea, vomiting, and dizziness associated with a range of causes including motion sickness, postoperative nausea and vomiting (PONV), vertigo, labyrinthine disorders, and nausea associated with opioid therapy.
Unlike many first-generation antihistamines used primarily for allergy, cyclizine's clinical use is dominated by its antiemetic and vestibular applications. It acts on the vomiting centre in the brain, the vestibular system, and the chemoreceptor trigger zone, providing broad-spectrum antiemetic coverage. Its sedating properties — a class effect of first-generation antihistamines — can be advantageous in patients for whom rest and sleep are desired during nausea (e.g. postoperatively or during travel).
Cyclizine is available as tablets and, in hospital settings, as an injectable solution for parenteral use. It is suitable for adults and children over 6 years of age. It does not require prescription in all contexts but is prescribed at higher doses and in specific clinical settings.
Prescription-strength and injectable cyclizine require clinical assessment before prescribing — which can now be done quickly and conveniently through a telehealth consultation.
What Conditions Is Cyclizine Used For?
Cyclizine is prescribed for:
prevention and treatment of nausea, vomiting, and dizziness during travel by car, sea, or air.
commonly used in hospital settings as part of antiemetic protocols.
including labyrinthitis, vestibular neuritis, and Ménière's disease.
cyclizine is widely used in end-of-life care to control nausea, often via subcutaneous infusion.
frequently prescribed alongside opioid analgesics to counteract nausea as a side effect.
used under medical supervision as a second-line antiemetic in severe cases
Cyclizine is a first-generation antihistamine and causes sedation in most patients. Do not drive, operate heavy machinery, or perform tasks requiring alertness after taking cyclizine until you know how it affects you.
How Does Cyclizine Work?
Cyclizine exerts its antiemetic and antivertigo effects through several complementary receptor-blocking mechanisms:
H1 Histamine Receptor Antagonism — Cyclizine blocks H1 receptors in the vomiting centre (medullary emetic centre) and the vestibular nucleus. This reduces the sensitivity of the vomiting reflex to stimuli from the vestibular apparatus and from higher cortical inputs, making it effective for motion sickness and vertigo-related nausea.
Muscarinic Acetylcholine Receptor Antagonism — Cyclizine has significant anticholinergic activity. Anticholinergic blockade in the vestibular system reduces the aberrant signals from the inner ear that trigger nausea and vomiting in motion sickness and vestibular disorders.
Weak Dopamine D2 Blockade — Cyclizine has some activity at the chemoreceptor trigger zone (CTZ), though this is less prominent than with dedicated D2 antagonists like prochlorperazine.
Together, these mechanisms make cyclizine effective across a broad range of nausea aetiologies, including vestibular, chemoreceptor, and cortically-mediated causes.
Dosages & Administration
The correct dose depends on the type and severity of infection, age, weight, and kidney function. Always follow your clinician's instructions. The table below is for general reference only.
Administration Tips
For motion sickness, take cyclizine 30 minutes before the start of travel for best effect — it is more effective as a preventative than a treatment once nausea has started. Take with water, with or without food. If nausea makes swallowing tablets difficult, the parenteral form may be more appropriate in a hospital setting. Avoid alcohol during cyclizine treatment — cyclizine markedly enhances the sedative effect of alcohol. Do not drive or operate machinery until you are confident cyclizine does not affect your alertness — sedation is very common, particularly with the first few doses. Use for the shortest necessary duration — cyclizine is intended for short-term management of nausea. Prolonged use is associated with tolerance and increasing anticholinergic side effects.
Side Effects of Cyclizine
Cyclizine's side-effect profile reflects its antihistaminic and anticholinergic properties.
- Drowsiness and sedation (very common)
- Dry mouth
- Blurred vision
- Urinary hesitancy or retention
- Constipation
- Headache
- Dizziness
- Acute angle-closure glaucoma — eye pain, blurred vision, haloes; precipitated by pupil dilation in susceptible individuals
- Urinary retention — particularly in men with prostate enlargement
- Severe anticholinergic toxicity — agitation, confusion, hallucinations, hyperthermia, tachycardia; particularly at high doses or in elderly patients
- Anaphylaxis — rare severe allergic reaction
Cyclizine's anticholinergic properties carry significant risks in elderly patients, including confusion, cognitive impairment, urinary retention, and increased falls. It appears on the Beers Criteria as a medication to be used with caution or avoided in older adults. Alternative antiemetics with a lower anticholinergic burden may be more appropriate in this population.
Drug Interactions
Always disclose all medications and supplements to your clinician or pharmacist before starting cyclizine.
Additive central nervous system and respiratory depression. Cyclizine and opioids are often co-prescribed deliberately (cyclizine to treat opioid-induced nausea), but this combination requires care as both are sedating.
Additive anticholinergic effects including dry mouth, urinary retention, constipation, and cognitive impairment. Particularly problematic in elderly patients.
Cyclizine's anticholinergic effects may antagonise the prokinetic effect of these agents.
Cyclizine may reduce the efficacy of levodopa in Parkinson's disease via central anticholinergic mechanisms
Important Warnings
Cyclizine is contraindicated in patients with narrow-angle (angle-closure) glaucoma, as its anticholinergic pupil-dilating effects can precipitate acute glaucoma — a medical emergency.
Cyclizine should be used with caution in patients with prostatic hypertrophy or other causes of bladder outflow obstruction, as anticholinergic effects may precipitate acute urinary retention.
Cyclizine is associated with significant anticholinergic side effects in elderly patients including confusion, hallucinations, and falls. It is included on the Beers Criteria as a medication requiring caution in older adults. Alternative antiemetics are often preferred in this group.
Cyclizine has been used for nausea and vomiting in pregnancy including hyperemesis gravidarum, and available evidence does not suggest significant teratogenic risk. However, it should be used under medical supervision during pregnancy, particularly in the first trimester. Consult your clinician.
Speak to a Clinician About Treatment
Getting advice no longer means sitting in a waiting room. Through The GP Service, you can consult with a licensed clinician in minutes — from home, on your lunch break, or wherever works for you. If treatment is clinically appropriate, your clinician can issue a prescription during the consultation. A consultation does not guarantee a prescription.
The treatment you need, when you need it.
Cyclizine FAQs
Both are effective antiemetics but work through different mechanisms. Cyclizine is primarily an antihistamine and anticholinergic agent, most effective for vestibular causes of nausea (motion sickness, labyrinthitis) and opioid-induced nausea. Prochlorperazine is primarily a dopamine antagonist, more effective for chemoreceptor-mediated nausea. Cyclizine is sedating; prochlorperazine carries risks of extrapyramidal effects. Your clinician will choose based on the cause of your nausea.
Cyclizine is absorbed relatively quickly after oral administration, with onset of action typically within 30 to 60 minutes. For motion sickness, it should be taken 30 minutes before the start of travel to achieve effective levels before nausea begins.
Cyclizine is sometimes prescribed for nausea and vomiting in pregnancy when first-line measures have not been sufficient. It has a reasonably established safety record in pregnancy. However, it should only be used under medical supervision and after discussion of all antiemetic options appropriate to the severity of symptoms.
Cyclizine itself is not classified as a controlled drug in standard formulations and does not have a recognised addiction potential in typical clinical use. However, misuse of injectable cyclizine in combination with opioids has been reported as a means of enhancing opioid effects. This is a concern primarily in opioid-dependent patients. Your clinician will be aware of this and monitor appropriately.