This is a vasodilator antihypertensive.

Indications: moderate to severe hypertension, in addition to a beta-adrenoceptor blocker or diuretics; hypertensive crisis.

Cautions: reduce initial dose in renal impairment; excessive reduction in blood pressure can occur with even low IV doses; may provoke angina in patients with coronary artery disease.

Contra-indications: porphyria, severe tachycardia, high output heart failure and cor pulmonale, systemic lupus erythematosus.

Side Effects: tachycardia, palpitation, flushing, hypotension, fluid retention, GI disturbances; headache, dizziness, systemic lupus erythematosus like syndrome with long term therapy with over 100 mg daily dose.

Dose: by mouth, 25 mg twice daily increased to max. of 50 mg twice daily.

By slow IV injection, 5-20 mg over 20 minutes; may be repeated after 20-30 minutes. By IV infusion, 20 mg repeated if necessary.