Effect of atenolol, metoprolol, and propranolol on isoproterenol-induced tremor and tachycardia in normal subjects

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Abstract
The effect of single oral doses of atenolol (100 mg), metoprolol (100 mg), propranolol (40 mg) and placebo on exercise tachycardia and on heart rate and finger tremor responses to graded injections of isoproterenol was investigated in 6 normal subjects. Propranolol was more potent than atenolol and metoprolol in suppressing the increase in heart rate and tremor amplitude produced by isoproterenol, even though at the dose used it was the least effective of all 3 drugs in decreasing exercise tachycardia. The data are consistent with the hypothesis that the suppression of isoproterenol-induced tremor is mediated by antagonism of peripheral .beta.2-adrenergic receptors; the possibility that a separate action other than .beta.-blockade may contribute to the tremorolytic action of propranolol cannot be excluded. The potential usefulness of examining the effect of .beta.-adrenoceptor blocking drugs on isoproterenol-induced tremor and tachycardia in cardioselectivity studies is discussed.