hydralazin

Hydralazine, sometimes spelled hydralazin in some sources, is a prescription vasodilator used to treat high blood pressure and certain heart conditions. It is a direct-acting arterial vasodilator that lowers systemic vascular resistance, thereby reducing blood pressure. The exact mechanism is not fully understood, but hydralazine appears to relax vascular smooth muscle and may increase cyclic GMP in the arteries, with a reflex sympathetic response that can produce tachycardia and fluid retention.

The drug is available in oral and injectable forms. After oral dosing, onset is typically 15 to 60 minutes with peak effects in 30 to 120 minutes; intravenous administration provides a more rapid effect. The elimination half-life is about 2 to 8 hours. Hydralazine is primarily metabolized by the liver and excreted in urine.

Indications include treatment of essential hypertension when other therapies are insufficient, management of hypertensive crises in hospital settings, and chronic heart failure when used in combination with nitrates (as the BiDil formulation). In pregnancy, hydralazine is used to control severe hypertension and preeclampsia when the benefits outweigh risks.

Common adverse effects include tachycardia, headaches, flushing, dizziness, and fluid retention; edema is frequent. Hypotension can occur, and a lupus-like syndrome may develop in slow acetylators. Caution is advised in patients with tachyarrhythmias, coronary artery disease, heart failure with reduced output, renal or hepatic impairment, or hypersensitivity.

Hydralazine interacts with other antihypertensives, increasing the risk of hypotension, and is often used with nitrates or diuretics. Brand-name forms include Apresoline. In pregnancy, it is categorized as a drug whose use requires careful clinical consideration.