hydralazine hydrochloride: clinical use

Prescribing considerations

• Use caution in coronary or cerebrovascular disease because reflex sympathetic stimulation may provoke angina or myocardial ischaemia.
• Ensure post-myocardial-infarction stabilisation before treatment.
• Renal or hepatic impairment can increase exposure and requires individual clinical adjustment.
• Prolonged exposure, slow acetylator status and female sex are associated with greater risk of lupus-like toxicity.
• Oral absorption and effect may be reduced by food.
• The tablet contains sucrose and is unsuitable for specified rare hereditary disorders of sugar metabolism.

Contraindications and cautions

• Hypersensitivity to hydralazine, relevant excipients or, for the injectable product, dihydralazine
• Idiopathic systemic lupus erythematosus or related disease
• Severe tachycardia or high-output heart failure, including that associated with thyrotoxicosis
• Myocardial insufficiency caused by mechanical obstruction, such as aortic or mitral stenosis or constrictive pericarditis
• Isolated right ventricular failure due to pulmonary hypertension
• Dissecting aortic aneurysm
• Porphyria

Monitoring

• Monitor blood pressure and heart rate, particularly during intravenous administration and treatment initiation.
• Assess for postural hypotension, tachycardia, angina, oedema and reduced urine output.
• Obtain a full blood count and antinuclear factor titre before and periodically during prolonged treatment, and investigate arthralgia, fever, rash, chest pain or persistent malaise promptly.
• Monitor renal and hepatic function when impaired or when toxicity is suspected.
• Remain alert for blood dyscrasias, lupus-like disease and ANCA-associated pulmonary–renal vasculitis.

Clinical pharmacology

Hydralazine is a direct arteriolar vasodilator with an incompletely defined mechanism. Reduced peripheral resistance produces reflex sympathetic activation and may cause sodium and fluid retention. Oral pharmacokinetics vary with acetylator phenotype because of first-pass metabolism; renal impairment can prolong elimination.

Formulation and product differences

• Tablets are for oral use and are licensed as adjunctive treatment for hypertension and selected chronic heart failure.
• The powder for concentrate is reconstituted for intravenous injection or infusion and is intended for monitored hospital treatment of hypertensive emergencies or hypertension with renal complications.
• The prepared intravenous solution is used promptly; unused remainder is discarded.

Tablet

Route: Oral

Strengths: 25 mg, 50 mg

Injection

Route: Parenteral

Strengths: 20 mg