1. Actions: Labetalol [lah-BET-a-lole] and carvedilol [CAR-ve-dil-ol] are reversible β-blockers with concurrent α1-blocking actions that produce peripheral vasodilation, thereby reducing blood pressure. They contrast with the other β-blockers that produce peripheral vasoconstriction, and they are therefore useful in treating hypertensive patients for whom increased peripheral vascular resistance is undesirable. They do not alter serum lipid or blood glucose levels. Carvedilol also decreases lipid peroxidation and vascular wall thickening, effects that have benefit in heart failure
2. Therapeutic use in hypertension: Labetalol is useful for treating the elderly or black hypertensive patient in whom increased peripheral vascular resistance is undesirable. [Note: In general, black hypertensive patients are not well controlled with β-blockers.] Labetalol may be employed as an alternative to methyldopa in the treatment of pregnancyinduced hypertension. Intravenous labetalol is also used to treat hypertensive emergencies, because it can rapidly lower blood pressure .
3. Adverse effects: Orthostatic hypotension and dizziness are associated with α1 blockade. Figure 7.10 summarizes the receptor specificities and uses of the β-adrenergic antagonists.
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