Obstetrics & Gynaecology/Hyperemesis gravidarum

Hyperemesis drugs

also: antiemetic pregnancy · cyclizine · promethazine · nausea vomiting pregnancy

Overview

Treatment of nausea & vomiting of pregnancy / hyperemesis gravidarum — the stepwise antiemetic choice and thiamine are the exam points.

Mechanism

Antihistamine/antidopaminergic antiemetics suppress the vomiting centre / CTZ. Thiamine prevents Wernicke encephalopathy in protracted vomiting. IV fluids + VTE prophylaxis address the complications.

Indications

Nausea & vomiting of pregnancy / hyperemesis gravidarum

The agents

Cyclizine / promethazine1st-line (antihistamine)

First-line in pregnancy.

Prochlorperazine1st-line (antidopaminergic)

Alternative first-line.

Ondansetron / metoclopramide2nd-line

Ondansetron: small cleft-palate signal (1st trimester) — counsel. Metoclopramide: EPSE, limit to 5 days.

Thiamine + IV fluids + VTE prophylaxissupportive

Thiamine prevents Wernicke; dehydration → VTE risk → LMWH.

Adverse effects

Ondansetron: small cleft-palate signal (early pregnancy)common

Metoclopramide: extrapyramidal reactionsserious

Limit duration.

Wernicke encephalopathy if thiamine omittedserious

Cautions & contraindications

Prolonged metoclopramideall

EPSE.

Interactions

Additive sedation/antimuscarinic effects

Monitoring & kinetics

Weight, ketones, U&E, fluid balance; consider admission if severe (PUQE score)

Oral/IV/IM/PR. Step up only if first-line antihistamine fails.

Source: RCOG — Nausea/vomiting of pregnancy (GTG69) · BNF — Antiemetics