[Use of labetalol in the treatment of hypertensive crises]

Labetalol, a combined alpha and beta adrenoceptor blocking drug, has been shown to be effective in the treatment of hypertensive crises when given intravenously. It also offers the advantage that treatment can be continued with the oral preparation. The purpose of our study was to evaluate if the administration of an intravenous bolus followed by an iv infusion and subsequently by the oral preparation might increase the efficacy of the drug without reducing its tolerance. Thirteen patients with severe essential hypertension and one with pheochromocytoma were treated during one or more hypertensive crises with Labetalol, 100 mg bolus i.v. injection in two minutes, followed by an intravenous infusion (2-4 mg/min for 60-90 minutes) and, one hour after the end of the infusion, by the oral preparation (200 mg t.i.d.). In 11 subjects with essential hypertension and in the patient with pheochromocytoma a 30% fall in systolic and diastolic blood pressure [from 240 +/- 10/155 +/- 6 mmHg (mean +/- 1 s.e.m.), to 162 +/- 8/111 +/- 6, p less than 0.01] was achieved within five minutes from the beginning of the treatment. Blood pressure remained well controlled thereafter, throughout the infusion period and during the first 24 hours of the oral administration. Heart rate fell simultaneously with the fall in blood pressure. Only in one patient blood pressure was not adequately controlled despite of the bolus and of an infusion at the rate of 4 mg/min for 20 minutes. In another case the fall in pressure caused near-fainting and the infusion was therefore not started. No other side effects were encountered except for transient orthostatic hypotension. We conclude that the administration of a bolus plus infusion of Labetalol is more effective than single or repeated boluses or graded infusions and it is equally well tolerated.