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Hydralazine

AEMPS

Direct arteriolar vasodilator

ATC code: C02DB02

Updated · Methodology

Indications

A

Hypertension in pregnancy

First line

Hypertensive emergency and preeclampsia. Per 222 (2020), NG133 2019, SEGO 2023 – IV agent for acute severe BP elevation in pregnancy (≥160/110). Dose 5–10 mg IV slowly, repeated every 20–30 min until BP control (max 30 mg). Alternative – IV labetalol. Not recommended for chronic oral BP control due to tachycardia and lupus-like syndrome.

Sources

  1. AEMPS: Ficha técnica de Hidralazina (2024)
  2. Cochrane Database Syst Rev: Drugs for treatment of very high blood pressure during pregnancy. (2013)
  3. BMJ: Hydralazine for treatment of severe hypertension in pregnancy: meta-analysis. (2003)
  4. Obstet Gynecol: ACOG Committee Opinion No. 767: Emergent Therapy for Acute-Onset, Severe Hypertension During Pregnancy and the Postpartum Period. (2019)

ICD-10: O13 · ICD-11: JA23

How to read tiers A–F
  • AStrong evidence – first or second line in international guidelines
  • BRecommended in selected cases
  • CStudy data contradict each other
  • DBenefit not proven, no documented harm
  • FDocumented harm, or risk without benefit

Mechanism of action

Direct arteriolar smooth muscle relaxation via interference with calcium metabolism and potassium channel activation. Lowers peripheral resistance, reflexively increases heart rate and cardiac output. Acts mainly on arteries, not veins. Short T½ 3–7 h.

Safety

Contraindications

  • Hypersensitivity
  • CHD, tachyarrhythmias
  • Aortic aneurysm
  • Severe hepatic impairment
  • Systemic lupus erythematosus

Serious adverse effects

  • Lupus-like syndrome with prolonged high-dose use
  • Hepatotoxicity
  • Peripheral neuropathy

Common adverse effects

  • Tachycardia
  • Headache
  • Flushing
  • Orthostatic hypotension
  • Nausea

Pregnancy: can you take Hydralazine?

Use as indicated for crisis control in any trimester.

Breastfeeding: can you take Hydralazine?

Hale L2 · Probably compatible

Compatible. Hale L2. RID 1.2%. Not first-line due to maternal tachycardia.

RID, infant dose via milk
1.2%
Maternal half-life
5 h
Maternal peak time
1 h
Peak milk concentration
0.13 mg/L
Milk-to-plasma ratio
1.4
Calculate RIDSafe feeding windowFull profile on NIH LactMed ↗

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Practical notes

Timing and administration

For hypertensive crisis in pregnancy – IV in hospital with continuous HR/BP monitoring, labetalol available as alternative. Fetal CTG monitoring when feasible.
Label mentions9 mentions

Verbatim lines from the interaction sections, in the language of the label

From this drug’s label

  • ModerateAINEclass named in the label
    «Uso concomitante que requiere ajuste posológico: Agentes antiinflamatorios no esteroideos (AINEs): el uso simultáneo puede disminuir su efecto antihipertensivo.»

    AEMPS, section 4.5 · Open on CIMA

  • Moderatebetabloqueantesclass named in the label
    «Uso concomitante que requiere ajuste posológico: Betabloqueantes (metoprolol, oxpenolol, propanolol): Existen estudios en los que se ha registrado posible aumento de la biodisponibilidad oral del…»

    AEMPS, section 4.5 · Open on CIMA

  • Moderatecorticosteroidesclass named in the label
    «Uso concomitante que requiere ajuste posológico: Corticosteroides: el uso simultáneo puede disminuir su efecto antihipertensivo.»

    AEMPS, section 4.5 · Open on CIMA

  • ModerateIMAOclass named in the label
    «Uso concomitante que requiere ajuste posológico: Inhibidores de la monoaminooxidasa: el uso simultáneo puede potenciar la hipotensión ortostática.»

    AEMPS, section 4.5 · Open on CIMA

  • ModerateMethylphenidate
    «Uso concomitante que requiere ajuste posológico: Metilfenidato: el uso simultáneo puede disminuir su efecto antihipertensivo.»

    AEMPS, section 4.5 · Open on CIMA

  • ModerateMetoprolol
    «Uso concomitante que requiere ajuste posológico: Betabloqueantes (metoprolol, oxpenolol, propanolol): Existen estudios en los que se ha registrado posible aumento de la biodisponibilidad oral del…»

    AEMPS, section 4.5 · Open on CIMA

  • Moderaterelajantes muscularesclass named in the label
    «Uso concomitante que requiere ajuste posológico: Relajantes musculares como baclofén y tizonidina, el uso simultáneo puede potenciar su efecto hipotensor.»

    AEMPS, section 4.5 · Open on CIMA

From other drugs’ labels

  • ModerateMetoprolol
    «Los pacientes que reciben tratamiento concomitante con otros beta-bloqueantes (p.ej. colirios) o inhibidores de la MAO deben mantenerse bajo estrecha vigilancia. En los pacientes que reciben…»

    AEMPS, section 4.5 · Open on CIMA

  • Enalapril
    «Other Cardiovascular Agents: Enalapril maleate has been used concomitantly with beta adrenergic-blocking agents, methyldopa, nitrates, calcium-blocking agents, hydralazine, prazosin and digoxin…»

    FDA, section 7 · Open on DailyMed

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Frequently asked

What is Hydralazine used for?

Hydralazine is evaluated for the following indications with varying evidence strength: Hypertension in pregnancy (evidence tier A), Hypertension during breastfeeding (evidence tier B). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Hydralazine?

Common side effects of Hydralazine (≥ 1 in 100): Tachycardia, Headache, Flushing, Orthostatic hypotension, Nausea. See the Safety section for uncommon and serious reactions.

Is Hydralazine safe during pregnancy?

Use as indicated for crisis control in any trimester.

Is Hydralazine compatible with breastfeeding?

Compatible. Hale L2. RID 1.2%. Not first-line due to maternal tachycardia.

Who should not take Hydralazine?

Hydralazine is contraindicated in: Hypersensitivity; CHD, tachyarrhythmias; Aortic aneurysm; Severe hepatic impairment; Systemic lupus erythematosus. Full list in the Safety section.

Official sources

Direct links to regulator labels. Open in a new tab.

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