Atenolol and Timolol, Two New Systemic β-Adrenoceptor Antagonists

ATENOLOL (Tenormin) and timolol (Blocadren) are two β-adrenoceptor antagonists recently released for clinical use in the United States (Fig. 1). They are the fourth and fifth systemic β-blockers to be approved by the Food and Drug Administration for the treatment of hypertension. Atenolol was released in 1981; like metoprolol, it is a β1-selective adrenergic blocker. However, unlike metoprolol, it has a long plasma half-life, which allows single daily doses in the treatment of hypertension.1 2 3 Timolol is a nonselective β-adrenergic blocker that has characteristics similar to those of propranolol but lacks membrane-stabilizing activity.1 It was approved by the FDA . . .