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Antihistamine Antiemetic — Hyperemesis Gravidarum Pregnancy: First-line antiemetic in pregnancy — well-established safety record

Cyclizine (Nausea and Vomiting in Pregnancy)

Brand names: Valoid

Adult dose

Dose: 50 mg oral / IV / IM three times daily
Route: Oral / Intravenous / Intramuscular
Frequency: Up to three times daily
Max: 150 mg/day
RCOG Green-top 69 (2024): Cyclizine is first-line antiemetic for nausea and vomiting in pregnancy. IV cyclizine 50 mg over 3-5 minutes for hospitalised hyperemesis patients

Paediatric dose

Dose: Not applicable in this obstetric context N/A/kg
Route: Oral / IV
Frequency: N/A
Max: N/A
Maternal medication

Dose adjustments

Renal

Use with caution

Hepatic

Use with caution in severe hepatic impairment

Paediatric weight-based calculator

Maternal medication

Clinical pearls

  • RCOG Green-top 69 (2024): Updated guideline — cyclizine is first-line antiemetic for NVP and hyperemesis gravidarum in UK; extensive safety data throughout pregnancy with no confirmed teratogenicity
  • Step-up approach for hyperemesis gravidarum: lifestyle measures → antihistamines (cyclizine) → metoclopramide or prochlorperazine → ondansetron (after careful MHRA discussion) → corticosteroids
  • IV cyclizine: give slowly over 3-5 minutes — rapid injection causes tachycardia and hypotension (histamine release); irritant to veins — flush with saline before and after
  • Rehydration equally important: ensure IV fluid resuscitation with electrolyte replacement in hospitalised HG — thiamine (Pabrinex) before glucose-containing fluids to prevent Wernicke encephalopathy
  • Prolonged anticholinergic use in pregnancy: monitor for urinary retention and constipation which can exacerbate discomfort in hyperemesis patients

Contraindications

  • Urinary retention
  • Narrow-angle glaucoma

Side effects

  • Drowsiness
  • Dry mouth
  • Urinary retention
  • Constipation
  • Tachycardia (IV)

Interactions

  • CNS depressants (additive sedation)
  • Anticholinergics (additive effects)

Monitoring

  • Symptom response (PUQE score)
  • Fluid balance and electrolytes
  • Vitamin B1 (thiamine) status in prolonged hyperemesis
  • Weight

Reference: BNFc; BNF 90; RCOG Green-top 69 (Hyperemesis Gravidarum 2024); NICE NG201. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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