A Comparison of the Cardioselectivity of Five β-Adrenoceptor Blocking Drugs

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Abstract
The cardioselectivities of five .beta.-adrenoceptor antagonists were compared. Six normal subjects received, in a double-blind random order, 200 mg acebutolol, 50 mg atenolol, 10 mg betaxolol, 100 mg metoprolol, 80 mg propranolol, and placebo. All .beta.-adrenoceptor antagonists produced a similar reduction in exercise tachycardia. Isoprenaline infusions in incremental doses were given. Dose-response curves were constructed and the doses of isoprenaline required to increase heart rate by 25 beats/min (I25), forearm blood flow by 3 ml/100 ml/min (IF3), and finger tremor by 200% (IT200), and decrease diastolic blood pressure by 25 mm Hg (ID25), after each treatment were compared. After propranolol, I25, ID25, IF3, and IT200 were greater (p < 0.02) than after atenolol, betaxolol and metoprolol; I25, ID25, and IT200 were greater than after acebutolol. After acebutolol I25, ID25, and IF3 were greater than after atenolol and betaxolol; IT200 was greater than after betaxolol. Atenolol and betaxolol caused less reduction in the isoprenaline-induced changes in blood glucose, plasma potassium, lactate, renin activity, and serum insulin than propranolol. Acebutalol caused less attenuation of blood glucose and plasma lactate, and metoprolol less attenuation of plasma renin activity, than propranolol. It is concluded that acebutolol, atenolol, betaxolol, and metoprolol cause less blockade of .beta.2-adrenoceptors than propranolol, and atenolol and betaxolol are more cardioselective than acebutolol.

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