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Direct vasodilator Pregnancy: Use before the third trimester should be avoided; may be used in later pregnancy if no safer alternative or the disease carries serious risks (e.g. pre-eclampsia/eclampsia). Crosses the placenta. Passes into breast milk but no adverse infant effects reported; breast-feeding possible with infant monitoring.

Hydralazine hydrochloride

Brand names: Apresoline

Used in: Pre-eclampsia & Obstetric Emergencies

Hydralazine hydrochloride is a directly acting arterial vasodilator used for hypertension (including hypertensive emergencies and in pregnancy by injection) and, combined with a nitrate, as an option in heart failure.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Hypertension: initially 25 mg twice a day
Route: Oral
Frequency: Twice a day (hypertension), increased gradually
Max: Not exceeding 200 mg daily; do not exceed 100 mg daily without first checking the patient's acetylator status; maximum dose in women should not exceed 100 mg
UK SPC (Apresoline Tablets 25 mg). Hypertension: begin with low doses and increase stepwise to optimal effect; initially 25 mg twice a day, increased gradually to a dose not exceeding 200 mg daily. Do not increase beyond 100 mg daily without first checking acetylator status; maximum dose in women should not exceed 100 mg. Chronic congestive heart failure: always initiate in hospital with haemodynamic monitoring; doses are generally higher than for hypertension — after progressive titration (initially 25 mg three or four times a day, increasing every second day) the maintenance dosage averages 50–75 mg four times a day. Not recommended for paediatric use. No special dosage regimen needed in the elderly, but renal elimination may diminish with age.

Dose adjustments

Renal

In moderate to severe renal impairment (creatinine clearance <30 mL/min or serum creatinine >2.5 mg/100 mL / 221 µmol/L) or hepatic dysfunction, adapt the dose or dosing interval according to clinical response to avoid accumulation.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substance or to any excipient
  • Idiopathic systemic lupus erythematosus (SLE) and related diseases
  • Severe tachycardia and heart failure with a high cardiac output (e.g. in thyrotoxicosis)
  • Myocardial insufficiency due to mechanical obstruction (e.g. aortic or mitral stenosis, constrictive pericarditis)
  • Isolated right ventricular failure due to pulmonary hypertension
  • Porphyria
  • Dissecting aortic aneurysm

Side effects

  • Tachycardia, palpitations (very common)
  • Headache (very common)
  • Flushing, hypotension (common)
  • Angina pectoris (common); gastrointestinal disturbances, diarrhoea, nausea, vomiting (common)
  • SLE-like syndrome (common; may be fatal); arthralgia, joint swelling, myalgia (common)

Interactions

  • Beta-blockers / sympatholytic agents — patients with suspected/confirmed coronary artery disease should receive hydralazine only under beta-blocker cover (start beta-blocker a few days before)
  • Adrenaline — do not use to correct hypotension during surgery in hydralazine-treated patients (hydralazine enhances the cardiac accelerating effect)

Clinical monograph

How it works

It relaxes arteriolar smooth muscle to reduce systemic vascular resistance and afterload; the resulting fall in blood pressure can trigger reflex tachycardia and fluid retention.

Prescribing in practice

  • Long-term use, particularly at higher doses or in slow acetylators, can cause a drug-induced lupus-like syndrome, so persistent arthralgia, rash or systemic symptoms should prompt review.
  • Reflex tachycardia and sodium and water retention often necessitate co-prescription of a beta-blocker and a diuretic.
  • It can precipitate or worsen angina and should be used with caution in coronary artery disease.

Monitoring

Monitor blood pressure and heart rate, with review for lupus-like symptoms (and antinuclear antibodies if suspected) during prolonged therapy.

Counselling the patient

  • Report persistent joint pain, unexplained fever or a facial rash.
  • Palpitations and headache can occur as your body adjusts.
  • Rise slowly from sitting or lying to reduce dizziness.

Evidence & guidelines

The combination of hydralazine with a nitrate is supported in heart failure, notably in the A-HeFT trial in self-identified Black patients.

Reference: NICE NG133; ESC guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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