Acute effect of intravenous labetalol in the treatment of systemic arterial hypertension.

1 The acute anti-hypertensive effect of intravenously administered labetalol, a combined alpha- and beta-adrenoreceptor antagonist, has been assessed in a pilot study involving 17 hypertensive patients. 2 In 11 patients with mild to moderately severe hypertension, there was a decrease in mean arterial pressure (24 mmHg) after a single intravenous dose of 50 mg labetalol. The peak response occurred approximately 4 min after administration of the drug. 3 In six patients with severe hypertension, there was a reduction in mean arterial pressure of 19 mmHg, but this was achieved after a further 50-mg dose administered 30 min after the initial injection. 4 In neither group was there any clinically significant decrease in heart rate, and drug-related side-effects were insignificant. 5 Labetalol reduced the blood pressure when administered intravenously and thus merits further investigation as a treatment for acute hypertensive crises.