Abstract
A new antihypertensive agent, labetalol, has potent hypotensive effects in the anesthetized rat and dog when given intravenously and also in the unanesthetized beagle when given orally. Labetalol slightly increased renal blood flow of the anesthetized dog while decreasing blood pressure. Labetalol slightly increased blood flow of canine femoral artery under constant pressure perfusion. However as compared with hydralazine, labetalol seems to have no marked vasodilatatory effect which accounts for its hypotensive effect.
Pharmacologically, labetalol possessed both α- and β-blocking activities, though weaker than phentolamine and propranolol respectively. Another specific action of labetalol was that it has stronger β-blocking action on β1 receptor (heart rate response) than on β2 receptor (blood pressure response). Like several other β-blockers, Labetalol seems to block neuronal uptake of noradrenaline.
