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Cyclizine in Pregnancy: Safety, Dosage & Side Effects

Cyclizine is one of the most commonly prescribed anti-sickness medications for pregnancy nausea and vomiting in the UK. If your GP has suggested it - or you're wondering if you should ask about it - here's everything you need to know.

Table of Contents

  1. What Is Cyclizine?
  2. How It Works
  3. Is Cyclizine Safe in Pregnancy?
  4. Dosage
  5. Side Effects
  6. How to Take It Effectively
  7. When Cyclizine Isn't Enough
  8. FAQ

What Is Cyclizine?

Cyclizine is an antihistamine medication that's used to treat nausea and vomiting. It's been used in pregnancy for decades and is one of the first medications GPs prescribe for morning sickness and hyperemesis gravidarum (HG) in the UK.

Key Facts

  • Drug class: Antihistamine (H1 receptor antagonist)
  • Brand names: Often sold combined with other drugs; cyclizine alone may be prescribed as the generic
  • Availability: Prescription only in the UK for pregnancy use
  • Form: Tablets (50mg), or injection for hospital use
  • Pregnancy safety: Considered safe - used for decades

How It Works

Cyclizine works by blocking histamine (H1) receptors in the brain. These receptors are involved in the vomiting reflex. By blocking them, cyclizine reduces the signals that trigger nausea and vomiting.

Why It Helps in Pregnancy

Pregnancy nausea is thought to be driven by hCG, oestrogen, and other hormones that affect the brain's vomiting centre. Cyclizine helps calm this centre, reducing the urge to vomit.

How Quickly It Works

  • Oral tablets: 30-60 minutes to take effect
  • Peak effect: 2-4 hours after taking
  • Duration: 4-6 hours of relief per dose

Is Cyclizine Safe in Pregnancy?

### The Evidence

Cyclizine has been used to treat nausea and vomiting in pregnancy since the 1950s. This long history means there's substantial data on its safety:

  • Large studies have found no increased risk of birth defects with cyclizine use in pregnancy
  • No evidence of harm to the baby when used at recommended doses
  • No evidence of increased miscarriage risk
  • Considered safe by the UK's RCOG and NICE guidelines

The Balance of Risk

Untreated severe nausea and vomiting can lead to:

  • Dehydration
  • Weight loss
  • Electrolyte imbalances
  • Nutritional deficiencies
  • Hospital admission

These pose a greater risk to your pregnancy than the medication does. Treating severe symptoms with cyclizine is safer than leaving them untreated.

When Safety Is a Concern

Cyclizine is not suitable for women with:

  • Known allergy to cyclizine
  • Severe liver disease
  • Certain heart conditions
  • Glaucoma (use with caution)

Always tell your GP about any existing conditions before taking cyclizine.

Dosage

### Standard Dose - **50mg up to three times daily** (maximum 150mg per 24 hours) - Take at regular intervals to maintain steady levels

Adjusting Your Dose

  • Start lower if you're concerned about drowsiness (e.g., 50mg twice daily)
  • Increase gradually if symptoms aren't controlled
  • Spread doses evenly - every 8 hours is typical
  • Take at bedtime to help with morning symptoms

How to Take

  • With or without food - taking with food may reduce stomach upset
  • Swallow whole with water
  • Don't crush or chew tablets

If You Miss a Dose

  • Take it as soon as you remember
  • If it's nearly time for the next dose, skip the missed one
  • Don't take a double dose to make up

Overdose

If you take too much, contact NHS 111 or go to A&E immediately. Symptoms of overdose include severe drowsiness, confusion, and rapid heartbeat.

Side Effects

### Common Side Effects - **Drowsiness**: The most common side effect. May affect driving and concentration. - **Dry mouth**: Sip water, chew sugar-free gum - **Dizziness**: Stand up slowly - **Blurred vision**: Usually mild - **Constipation**: Drink water and eat fibre - **Difficulty urinating**: Report to your GP if significant

Less Common Side Effects

  • Headache
  • Restlessness
  • Tremor
  • Palpitations
  • Skin rash (allergic reaction - stop and contact GP)

Managing Side Effects

  • Drowsiness: Take a larger dose at bedtime
  • Dry mouth: Stay hydrated, use sugar-free gum
  • Dizziness: Avoid standing up quickly
  • Constipation: Increase fluid and fibre intake

When to Contact Your GP

  • Severe drowsiness affecting daily life
  • Difficulty urinating
  • Rapid or irregular heartbeat
  • Allergic reaction (rash, swelling, breathing difficulty)
  • Symptoms not improving after 72 hours

How to Take It Effectively

### Timing Matters - **Take regularly**, not just when you feel sick - **Prevention is better** than treating after vomiting starts - **Schedule doses** at consistent times (set alarms) - **Take a dose before bed** to help with morning symptoms

Combining with Other Treatments

Cyclizine can be safely combined with:

  • Ginger (tea, supplements)
  • Acupressure wristbands
  • Vitamin B6
  • Other anti-sickness medications (as prescribed by your GP)

What to Do If You Vomit After Taking It

  • If you vomit within 30 minutes of taking cyclizine, take another dose
  • If you vomit after 30-60 minutes, you may have absorbed enough - wait for the next scheduled dose
  • If you're consistently vomiting doses, ask your GP about buccal (dissolvable) alternatives or combining with another medication

Don't Stop Suddenly

If you feel better, don't stop taking cyclizine abruptly - it's the medication keeping you stable. Talk to your GP about gradually reducing the dose when your symptoms have been controlled for several days.

When Cyclizine Isn't Enough

### Signs Cyclizine Alone Isn't Working - Still vomiting 3+ times daily after 48-72 hours - Can't keep water down - Losing weight - Feeling dehydrated

What Your GP May Suggest

  1. Add a second medication (e.g., prochlorperazine or ondansetron)
  2. Switch to a different medication (e.g., promethazine)
  3. Refer you to a specialist (obstetrician)
  4. Hospital admission for IV fluids and medication

Combination Therapy

Many women need two or more medications. This is normal and not a sign that you're "failing." HG and severe nausea often require combination treatment. Read our guide to anti-sickness medication in pregnancy for more on combination options.

Frequently Asked Questions

### Is cyclizine safe in pregnancy?

Yes. Cyclizine has been used to treat nausea and vomiting in pregnancy for decades. Large studies have found no increased risk of birth defects or miscarriage. It's considered safe by RCOG and NICE guidelines.

How much cyclizine can I take in pregnancy?

The standard dose is 50mg up to three times daily (maximum 150mg per 24 hours). Always follow your GP's specific instructions. Start with a lower dose if you're concerned about drowsiness.

Will cyclizine make me drowsy?

Drowsiness is the most common side effect of cyclizine. It can range from mild to significant. If drowsiness is a problem, try taking a larger dose at bedtime or ask your GP about adjusting your dose.

Can I take cyclizine throughout my pregnancy?

Most women only need cyclizine for the first trimester. However, some women with HG need it throughout pregnancy. Your GP will review your medication regularly and reduce it when appropriate.

What if cyclizine doesn't work?

If cyclizine isn't working after 48-72 hours, your GP can add a second medication (like prochlorperazine or ondansetron), switch you to a different medication, or refer you to a specialist. Don't accept being told there's nothing else - there are several options.

Further reading:

This article is for informational purposes only and does not constitute medical advice. Always consult your GP or midwife with any concerns about your pregnancy.

Last reviewed: June 2026

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