Vasodilator (Antihypertensive) Pregnancy: Used in pregnancy for hypertensive emergency — established safety record

Hydralazine (IV — Acute Hypertension in Pregnancy)

Brand names: Apresoline

Adult dose

Dose: 5 mg IV bolus over 15–20 min; repeat every 20 min to a max of 20 mg total

Route: IV slow bolus

Frequency: Repeat every 20 min PRN (max 20 mg total)

Max: 20 mg total IV

Dilute 20 mg in 20 mL normal saline for IV use. Alternative: IV infusion 0.5–10 mg/hr. Target systolic BP 140–150 mmHg and diastolic 80–100 mmHg per NICE NG133. Onset 10–20 min, duration 3–8h.

Paediatric dose

Route: N/A

Frequency: N/A

Max: N/A

Not applicable in obstetric indication

Dose adjustments

Renal

Caution in renal impairment — reduce dose

Hepatic

Caution in hepatic impairment

Clinical pearls

Third-line IV antihypertensive in pregnancy after labetalol and nifedipine (per NICE NG133 preference hierarchy)
Always dilute before IV use — rapid IV bolus of undiluted hydralazine causes precipitous BP drop
Reflex tachycardia is common — monitor fetal heart rate on CTG throughout
Useful when labetalol is contraindicated (e.g., asthma, severe bradycardia)
Slower onset than labetalol — 10–20 min; do not repeat too quickly

Contraindications

Dissecting aortic aneurysm
Idiopathic systemic lupus erythematosus
Severe tachycardia or high output cardiac failure
Myocardial insufficiency

Side effects

Reflex tachycardia (common)
Headache
Flushing
Palpitations
Hypotension (over-treatment)
Nausea

Interactions

Diazoxide — profound hypotension
MAOIs — enhanced hypotensive effect
Beta-blockers — co-administration reduces reflex tachycardia

Monitoring

Blood pressure (every 5 min after each dose)
Fetal heart rate (continuous CTG)
Maternal HR (reflex tachycardia)
Symptoms of hypoperfusion

Reference: BNFc; NICE NG133 Hypertension in Pregnancy; RCOG Green-top 10A Eclampsia; BNF. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways