Pharmacologic basis for the use of doxazosin in the treatment of essential hypertension

Abstract

The drug treatment of mild hypertension has been shown to afford protection against fatal and nonfatal strokes, congestive heart failure, progression to more severe levels of hypertension, and all-cause mortality, but not against the complications of coronary artery disease. The lack of benefit against coronary artery disease may result from failure to reduce other risk factors or because the drugs employed increased coronary risk. It can be taken as axiomatic that effective preventive antihypertensive therapy is more likely with drugs with mechanisms and sites of action that are focused on the underlying pathophysiology than with drugs that lower blood pressure by means unrelated to the hypertensive process. Adrenergic predominance plays a major role in the initiation and maintenance of essential hypertension and, consequently, the alpha-adrenergic receptor inhibitors were among the first substances to receive serious consideration as antihypertensive agents. However, since these drugs are nonselective, feedback control of transmitter norepinephrine was lost and, consequently, the clinical expectations of the early alpha-adrenergic receptor inhibitors in the treatment of high blood pressure were not fulfilled. The discovery of selective postjunctional alpha 1-adrenergic-receptor inhibitors, such as prazosin and doxazosin, which preserve feedback control of transmitter norepinephrine release, was the crucially important step in the development of specific drugs to combat the hyperactivity of adrenergic vasoconstrictor nerves in hypertension. These drugs have been shown to normalize hemodynamics in hypertensive patients. They lower blood pressure through a reduction in peripheral resistance at rest and during exercise, independent of changes in heart rate and blood pressure, with minimal reflex activation or tolerance development. Alpha 1-adrenergic-receptor inhibitors, such as prazosin and doxazosin, represent an attractive choice for initial therapy in all grades of hypertension and are especially appropriate in hypertensive patients with congestive heart failure, asthma and chronic obstructive airways disease, renal impairment, diabetes mellitus, hyperlipidemia, benign prostatic hyperplasia, or gout, and in those involved in vigorous work, sports, or exercise. There are no known contraindications to these drugs, except in patients who are sensitive to quinazolines.