ANTIHYPERTENSIVE AND HEMODYNAMIC ACTIONS OF SCH-19927, THE R,R-ISOMER OF LABETALOL

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  • 1 January 1981
    • journal article
    • research article
    • Vol. 218  (2) , 444-452
Abstract
SCH 19927, 1 of the 4 chiral forms of labetalol, is .apprx. 4 times as potent a .beta.-adrenergic receptor blocker as the parent racemate, but is only 1/3 as potent in blocking .alpha.-receptors. Its antihypertensive and hemodynamic actions are described. SCH 19927 and labetalol lowered blood pressure in hypertensive rats and dogs. SCH 19927 was somewhat more effective at lower doses, but the 2 agents produced comparable responses at higher doses. Both reduced blood pressure and peripheral resistance and increased cardiac output in anesthetized dogs. Intraarterial injection into the femoral vascular bed, in the presence or absence of neurogenic vasoconstrictor tone, resulted in dose-related vasodilation. .alpha.-Blockers, e.g., phentolamine and prazosin, are essentially devoid of vasodilator activity in denervated beds. Vasodilatation is largely responsible for the antihypertensive response to labetalol and particularly to SCH 19927. SCH 19927 is a potentially useful agent which would be expected to reduce pressure in humans by 2 complementary mechanisms, .beta.-blockade and vasodilatation. It should possess less orthostatic potential than labetalol.