Diazoxide vs labetalol: a cross-over comparison of short-term effects in hypertension

In a randomized cross-over study the acute effects of intravenous labetalol (1-2 mg/kg; mean dose 86.5 mg) were compared with those of diazoxide (3-5 mg/kg; mean dose 253.8 mg) in 13 severely hypertensive patients with diastolic blood pressure above 110 mm Hg (36.3 kPa) and a mean arterial pressure (MAP) of 165.4 mm Hg (22.0 kPa). Within five minutes following injection of both drugs an immediate fall in arterial pressure was observed (P less than 0.05), which was even more pronounced during subsequent minutes (P less than 0.01). The reduction in MAP after 30 minutes averaged 20% (P less than 0.01), with no significant differences between the drugs under trial or administration schedules. Diazoxide did not increase the heart rate as much as expected (P greater than 0.10), while labetalol slowed it down moderately but significantly (P less than 0.05). There were no notable changes in the blood levels of glucose and potassium and no particular side-effects were observed. It is concluded that the acute effects of intravenous labetalol are comparable to those of diazoxide and that labetalol can be used with advantage as a complemental alternative to diazoxide in the emergency treatment of some hypertensive crises.