Intravenous labetalol in hypertensive patients treated with beta-adrenoreceptor-blocking drugs.

1 The effect of intravenous injections of labetalol at doses of 1 and 2 mg/kg was studied in 15 patients with severe hypertension inadequately controlled by beta-adrenoreceptor-blocking drugs. 2 At a dose of 1 mg/kg there was a slight but statistically insignificant reduction in blood pressure. When 2 mg/kg was given there was a prolonged (6 h) significant reduction in lying blood pressure. At both dose levels there was a small initial increase in pulse rate but forced peak flow was not affected. 3 Side-effects were limited to transient postural hypotension and a feeling of warmth. 4 It is concluded that intravenous labetalol at a dose of 2 mg/kg is safe and effective in rapidly reducing blood pressure in patients already receiving beta-adrenoreceptor-blocking drugs.