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Vasodilator (Antihypertensive) Pregnancy: §4.6, verbatim: 'Women of child-bearing potential — Women planning to become pregnant should not take Apresoline. When pregnancy is confirmed in women taking Apresoline, the treatment should be discontinued immediately. Pregnancy — Use of Hydralazine in pregnancy, before the third trimester should be avoided but the drug maybe employed in later pregnancy if there is no safer alternative or when the disease itself carries serious risks for the mother or child e.g. pre-eclampsia and/or eclampsia. No serious adverse effects in human pregnancy have been reported to date with Hydralazine, although experience in the third trimester is extensive. However, studies have shown teratogenic potential in mice but not in other animal species. Hydralazine crosses the placenta. Breast-feeding — Hydralazine passes into breast milk but reports available so far have not shown adverse effects on the infant. Mothers in whom use of Hydralazine proves unavoidable may breast feed their infant provided that the infant is observed for possible adverse effects. Fertility — No data available.'

Hydralazine (IV — Acute Hypertension in Pregnancy)

Brand names: Apresoline

Used in: Pre-eclampsia & Obstetric Emergencies

Intravenous hydralazine, a directly acting arteriolar vasodilator, used to control acute severe hypertension in pregnancy and the peripartum period, including pre-eclampsia and eclampsia.

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: 5 to 10 mg by slow intravenous injection. §4.2 Adults, verbatim: 'Initially 5 to 10 mg by slow intravenous injection, to avoid precipitous decreases in arterial pressure with a critical reduction in cerebral or utero-placental perfusion.'
Route: Slow intravenous injection after reconstitution and dilution. §4.2 Method of administration: 'For Intravenous use only.' The same product may alternatively be given by continuous intravenous infusion (rates in notes).
Frequency: §4.2, verbatim: 'If necessary a repeat injection can be given after an interval of 20-30 minutes, throughout which blood pressure and heart rate should be monitored.'
Max: No maximum total dose is stated for this acute intravenous regimen anywhere in the fetched SPC — §4.2 gives an initial dose and a repeat interval but no ceiling and no cumulative limit. Do not infer one. (A 100 mg daily figure does appear in §4.4, but it belongs to PROLONGED MAINTENANCE therapy and the risk of SLE-like syndrome, not to this acute intravenous regimen — see notes.)
SCOPE: §4.1 Therapeutic indications was NOT in the fetched bundle, so the 5-10 mg figure is recorded as the SPC's general adult intravenous regimen for this parenteral product, not as an eclampsia-specific regimen; the SPC's own justification for the slow injection is written in terms of 'utero-placental perfusion' and §4.6 endorses use 'in later pregnancy... e.g. pre-eclampsia and/or eclampsia'. RESPONSE TARGET (§4.2, verbatim): 'A satisfactory response can be defined as a decrease in diastolic blood pressure to 90/100 mmHg.' No blood-pressure target from any national guideline is in this bundle — the target ranges previously shown on this page are not sourced here. PREPARATION (§4.2, verbatim): 'The contents of the vial should be reconstituted by dissolving in 1 ml of water for injection BP. This should then be further diluted with 10 ml of Sodium Chloride injection BP 0.9% and be administered by slow intravenous injection. The injection must be given immediately and any remainder discarded.' INFUSION (§4.2, verbatim, a RATE not a dose): 'Hydralazine may also be given by continuous intravenous infusion, beginning with a flow rate of 200-300 micrograms/min. Maintenance flow rates must be determined individually and are usually within the range 50-150 micrograms/min. The product reconstituted as for direct iv injection may be added via the infusion container to 500 ml of Sodium Chloride Injection BP 0.9% and given by continuous infusion. The addition should be made immediately before administration and the mixture should not be stored. Hydralazine for infusion can also be used with 5% sorbitol solution or isotonic inorganic infusion solutions such as Ringers solution.' ELDERLY (§4.2, verbatim): 'Clinical evidence would indicate that no special dosage regime is necessary. Advancing age does not affect either blood concentration or systemic clearance. Renal elimination may however be affected in so far as kidney function diminishes with age.' PROLONGED-THERAPY CEILING, RECORDED HERE AND NOT IN maxDose BECAUSE IT IS A DIFFERENT CONTEXT (§4.4, verbatim): 'it is recommended that for maintenance therapy the lowest effective dose should be used. If 100 mg daily fails to elicit an adequate clinical effect, the patient's acetylator status should be evaluated. Slow acetylators and women run greater risk of developing the SLE like syndrome and every effort should therefore be made to keep the dosage below 100 mg daily.' BETA-BLOCKER COVER (§4.4, verbatim): 'Patients with suspected or confirmed coronary artery disease should therefore be given Hydralazine only under beta-blocker cover or in combination with other suitable sympatholytic agents. It is important that the beta-blocker medication should be commenced a few days before the start of treatment with Hydralazine.' PERIOPERATIVE (§4.4, verbatim): 'When undergoing surgery, patients treated with Hydralazine may show a fall in blood pressure, in which case one should not use adrenaline to correct the hypotension, since it enhances the cardiac-accelerating effects of hydralazine.'

Dose adjustments

Renal

§4.2 Special Populations — Renal impairment and hepatic impairment (all indications), verbatim: 'In patients with moderate to severe renal impairment (creatinine clearance < 30 mL/min or serum creatinine concentration > 2.5 mg/100 mL or 221 micromol/L) or hepatic dysfunction, the dosage or the dosing interval must be adapted according to the clinical response to avoid accumulation of the "apparent" active substance (see section 4.4).' No numeric adjusted dose is given.

Hepatic

Covered by the same §4.2 sentence as renal impairment, verbatim: 'In patients with moderate to severe renal impairment... or hepatic dysfunction, the dosage or the dosing interval must be adapted according to the clinical response to avoid accumulation of the "apparent" active substance (see section 4.4).' No numeric adjusted dose is given.

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 of the excipients listed in section 6.1
  • Known hypersensitivity to dihydralazine
  • 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. in the presence of aortic or mitral stenosis or constrictive pericarditis)
  • Isolated right ventricular failure due to pulmonary hypertension (cor pulmonale)
  • Dissecting aortic aneurysm
  • Porphyria
  • Not a contraindication but a §4.2 exclusion: 'The safety and efficacy of Apresoline 20 mg Ampoules / Hydralazine 20mg Powder for Concentrate for Solution for Injection/Infusion in children have not yet been established.'

Side effects

  • Very common (>= 1/10): headache; tachycardia; palpitations
  • Common (>= 1/100 to < 1/10): angina pectoris; flushing; hypotension; gastrointestinal disturbances, diarrhoea, nausea, vomiting; SLE-like syndrome (§4.8 notes this 'sometimes resulting in a fatal outcome'); arthralgia, joint swelling, myalgia
  • Rare (>= 1/10 000 to < 1/1 000): anaemia, leucopenia, neutropenia, thrombocytopenia with or without purpura, eosinophilia; anorexia; agitation, anxiety; dizziness; conjunctivitis, increased lacrimation; heart failure; nasal congestion, dyspnoea, pleuritic pain; jaundice, hepatomegaly, abnormal liver function sometimes in association with hepatitis; hypersensitivity reactions such as pruritus, urticaria, vasculitis, rash; proteinuria, blood creatinine increased, haematuria sometimes in association with glomerulonephritis; pyrexia
  • Isolated cases: haemolytic anaemia, leucocytosis, lymphadenopathy, pancytopenia, splenomegaly, agranulocytosis; depression, hallucinations; peripheral neuritis, polyneuritis, paraesthesia ('these unwanted effects may be reversed by administering pyridoxine'); exophthalmos; paradoxical pressor responses; paralytic ileus; acute kidney failure, urinary retention. Not known: tremor; hepatosplenomegaly
  • §4.8 timing note, verbatim: 'Some of the adverse effects listed below e.g. tachycardia, palpitations, angina symptoms, flushing, headache, dizziness, nasal congestion and gastro-intestinal disturbances are commonly seen at the start of treatment, especially if the dose is raised quickly. However such effects generally subside in the further course of treatment.'
  • §4.4 SLE-like syndrome, verbatim: 'Prolonged treatment with hydralazine may provoke a systemic lupus erythematosus (SLE)-like syndrome. First symptoms are likely to be similar to rheumatoid arthritis (arthralgia, sometimes associated with fever, anaemia, leucopenia, thrombocytopenia and rash) and are reversible after withdrawal of the drug.'
  • §4.4 myocardial ischaemia, verbatim: 'Myocardial stimulation may provoke or aggravate angina pectoris. Hydralazine can cause anginal attacks and ECG changes indicative of myocardial ischaemia.'

Monitoring

  • Blood pressure and heart rate between doses (§4.2, verbatim): 'If necessary a repeat injection can be given after an interval of 20-30 minutes, throughout which blood pressure and heart rate should be monitored.'
  • Response target (§4.2, verbatim): 'A satisfactory response can be defined as a decrease in diastolic blood pressure to 90/100 mmHg.'
  • In heart failure (§4.4, verbatim): 'When initiating therapy in heart failure, particular caution should be exercised and the patient kept under surveillance and/or haemodynamic monitoring for early detection of postural hypotension or tachycardia.'
  • Acetylator status on prolonged therapy (§4.4, verbatim): 'If 100 mg daily fails to elicit an adequate clinical effect, the patient's acetylator status should be evaluated.'
  • SLE-like syndrome (§4.4, verbatim): 'Early detection and a timely diagnosis with appropriate therapy (i.e. treatment discontinuation and possibly long-term treatment with corticosteroids may be required to reverse these changes) are of utmost importance in this life-threatening illness to prevent more severe complications, which may sometimes be fatal.'
  • No fetal or cardiotocographic monitoring requirement appears anywhere in the fetched SPC — any such requirement must come from a guideline source, not from this bundle.

Clinical monograph

How it works

Hydralazine relaxes arteriolar smooth muscle, reducing systemic vascular resistance and arterial pressure; the resulting fall in blood pressure can trigger a reflex tachycardia.

Prescribing in practice

  • Blood pressure can fall abruptly, risking maternal hypotension and reduced uteroplacental perfusion with fetal distress, so it must be given by titrated doses with continuous maternal and fetal monitoring, and intravenous fluid co-loading is often considered.
  • Reflex tachycardia, headache, flushing and fluid retention are common and the clinical picture can mimic worsening pre-eclampsia.
  • It is one of several first-line options for acute severe hypertension in pregnancy and is administered only in a monitored obstetric or critical-care setting.

Monitoring

Monitor maternal blood pressure and heart rate frequently alongside cardiotocographic fetal monitoring during and after administration.

Counselling the patient

  • This medicine is given by drip or injection to bring dangerously high blood pressure down quickly and protect you and your baby.
  • You and your baby will be closely monitored throughout.
  • Tell staff if you feel faint, develop a pounding heartbeat or a severe headache.

Evidence & guidelines

NICE guidance on hypertension in pregnancy lists intravenous hydralazine among first-line agents for acute severe hypertension, used with careful titration and monitoring.

Reference: NICE NG133 Hypertension in Pregnancy; RCOG Green-top 10A Eclampsia; 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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