Studies on concurrent alpha- and beta-adrenoceptor blocking action of S-596 (arotinolol).

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The effects of a therapeutic dose of oral S-596 upon the cardiovascular response to intravenous isoproterenol and noradrenaline were studied in 2 hypertensive and 4 normotensive subjects in order to evaluate the drug's mode of action. After oral administration of S-596, mean blood pressure rose slightly and the heart rate decreased. In addition, cardiac output decreased considerably and total peripheral resistance increased. However pulmonary arterial end-diastolic pressure and right atrial pressure were not affected by S-596 administration. Before S-596, intravenous isoproterenol increased both heart rate and pulse pressure in a dose-dependent manner. Similarly, intravenous noradrenaline increased both systolic and diastolic pressures. Following 15mg of S-596, the effects of isoproterenol were antagonized such that the cumulative log-dose-response curves of the mean isoproterenol-induced increases in heart rate and reductions in diastolic pressure were shifted in parallel to the right. At the same time, the mean noradrenaline-induced increases in blood pressure were also antagonized in a competitive manner.The mean ratio of alpha- and beta-components was calculated as:isoproterenol dose ratio/noradrenaline dose ratio=7.88From this result it can be suggested that the alpha-adrenoceptor blockade potency of this drug is approximately one-eight of its beta-adrenoceptor blockade potency.
International Heart Journal刊行会の論文