α-Adrenoceptor Antagonists (or α-blockers) block postsynaptic α1-receptors, relax smooth muscle and reduce blood pressure by lowering peripheral vascular resistance. These drugs are effective as monotherapy in some individuals, but tachyphylaxis may appear during long-term therapy and AEs are relatively common. The most prominent side effect is hypotension. Thus, they should generally not be used as initial drugs to treat hypertension except in men with symptomatic prostatism.
Drugs with central sympatholytic action lower blood pressure by stimulating α-adrenergic receptors in the central nervous system, thus reducing efferent peripheral sympathetic outflow. These drugs are effective as monotherapy in some patients, but they are usually used as second or third-line drugs because of the high frequency of drug intolerance, including sedation, fatigue, dry mouth, postural hypotension and impotence.
Arteriolar dilators relax vascular smooth muscle and produce peripheral vasodilation. When given alone, they stimulate reflex tachycardia, increase myocardial contractility and cause headache, palpitations and fluid retention. They are usually given in combination with Ds and BBs in resistant patients.
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