When a hypertensive crisis occurs during pregnancy, rapid control of blood pressure is necessary to limit such complications as stroke, placental abruption, eclampsia, or maternal death. Both diazoxide and hydralazine are potentially useful antihypertensive drugs for rapidly lowering blood pressure, but there is concern that diazoxide might cause serious hypotension. In contrast, there is some evidence that diazoxide may be preferable to hydralazine because it modulates immune function and has an antiinflammatory effect on the placenta. This prospective randomized, open-label study enrolled 124 antenatal or postnatal women with severe hypertension, defined as a systolic blood pressure exceeding 170 mm Hg or a diastolic pressure greater than 110 mm Hg. Participants were randomized to receive 5-mg doses of hydralazine or 15-mg doses of mini-bolus diazoxide intravenously.
The time needed to control blood pressure averaged 34 minutes with hydralazine and 19 minutes with diazoxide, a significant difference. The median number of doses of hydralazine was 2, and of diazoxide, 7. There were no hypotensive episodes in patients given diazoxide and only one such episode in a hydralazine-treated patient. Episodes of persistent severe hypertension were more frequent with hydralazine therapy than with diazoxide (38% vs. 16%). Cesarean deliveries undertaken because of a nonreassuring cardiotocograph were comparably frequent in the 2 treatment groups. Neonatal outcomes also were similar.
The investigators conclude that diazoxide is an effective and safe treatment for pregnant women with severe hypertension. The present regimen of 15-mg doses lowered blood pressure in pregnant women with persistent severe hypertension without causing hypotension. Hydralazine also proved to be an effective and relatively safe antihypertensive agent in this setting.