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Antiemetic (Antihistamine H₁ Antagonist) Pregnancy: Compatible — widely used for hyperemesis gravidarum (Cyclizine + pyridoxine is first-line). No significant teratogenicity signal.

Cyclizine

Brand names: Valoid

Adult dose

Dose: 50mg up to three times daily (oral, IV, or IM). Palliative care: 150mg/24 hours by continuous subcutaneous infusion (CSCI).
Route: Oral, IV (slow — over at least 1 minute), IM, or SC infusion
Frequency: Up to three times daily
Max: 150mg/day
Useful for vestibular nausea (motion sickness, labyrinthitis), opioid-induced nausea, raised intracranial pressure nausea. IV: give slowly — rapid IV injection causes severe tachycardia and facial flushing. Compatible with diamorphine and morphine in syringe drivers (CSCI). Incompatible with metoclopramide and haloperidol in syringe drivers.

Paediatric dose

Dose: 1 mg/kg
Route: Oral, IV (slow), or IM
Frequency: Up to three times daily
Max: 25mg per dose (children ≥6 years)
BNF for Children: 1 month–5 years: 0.5–1mg/kg (max 25mg) up to TDS; 6–11 years: 25mg up to TDS; 12–17 years: 50mg up to TDS. IV: give over at least 1 minute. Source: BNF for Children 2024.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

Use with caution in hepatic impairment — increased sedation risk.

Paediatric weight-based calculator

BNF for Children: 1 month–5 years: 0.5–1mg/kg (max 25mg) up to TDS; 6–11 years: 25mg up to TDS; 12–17 years: 50mg up to TDS. IV: give over at least 1 minute. Source: BNF for Children 2024.

Clinical pearls

  • Mechanism: H₁ and muscarinic antagonism — effective for vestibular, opioid-induced, and motion-related nausea. Less effective for chemotherapy-induced nausea (5-HT3 pathway dominant).
  • Palliative care syringe driver: cyclizine 150mg/24h is compatible with morphine or diamorphine — but incompatible with metoclopramide, haloperidol, or ketorolac in the same syringe.
  • Rapid IV injection causes severe tachycardia and flushing (histamine release) — always give IV slowly over at least 1 minute.
  • Motion sickness: take 30 minutes before travel. Transdermal hyoscine (Scopoderm patch) is an alternative for prolonged journeys.

Contraindications

  • Known hypersensitivity to cyclizine
  • Severe heart failure (may exacerbate due to tachycardia and anticholinergic effects)
  • Porphyria (relative)

Side effects

  • Drowsiness (antihistamine effect)
  • Dry mouth, urinary retention (anticholinergic)
  • Tachycardia (especially with rapid IV injection)
  • Blurred vision
  • Paradoxical excitability in children (uncommon)

Interactions

  • Anticholinergic drugs: additive anticholinergic effects
  • CNS depressants (opioids, benzodiazepines, alcohol): enhanced sedation
  • Metoclopramide / haloperidol: incompatible in syringe driver — precipitates

Monitoring

  • Symptom response
  • Heart rate (IV route)
  • Anticholinergic burden in elderly

Reference: BNFc; BNF 90; NICE NG121 Nausea and Vomiting in Pregnancy; Palliative Care Formulary (PCF) 7th Edition. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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