Labetalol Versus Magnesium Sulfate (MgSO4) for the Prevention of Eclampsia Trial

Summary

Eclampsia is a major cause of perinatal morbidity and mortality. The pathophysiology is not known but magnetic resonance imaging (MRI) and Doppler data suggest that overperfusion of the cerebral tissues is a major etiologic factor. Hypertensive encephalopathy from overperfusion, and vascular damage from excessive arterial pressure (cerebral barotrauma) are believed to lead to vasogenic and cytotoxic cerebral edema, with resultant neuronal anomalies, seizure activity and cerebral bleeding if left unchecked. Doppler data have shown that cerebral perfusion pressure (CPP) is abnormally increased in severe preeclampsia and that autoregulation of the middle cerebral artery is affected by this condition leading to increased CPP. Magnesium sulfate (MgSO4) is the most widely accepted eclampsia treatment and prophylactic agent, and it has been used in the USA since the 1950's. Despite widespread use, its mechanism of action is unknown. MgSO4 is given intravenously or intramuscularly and requires specialized nursing training and monitoring to minimize toxicity from respiratory and cardiac depression. Labetalol, a combined alpha and beta blocker, has been used for many years to safely treat hypertension in preeclamptic women, and is now known to reduce CPP in women with preeclampsia. In the United Kingdom labetalol was for many years used as the sole agent in treating preeclampsia, and the rate of seizure was no different to that reported in the USA with MgSO4. Since labetalol can be administered orally, is economical, has low toxicity potential, does not require specialized training to administer or monitor, and decreases CPP, it may be an ideal agent for controlling blood pressure (BP) and decreasing the incidence of eclampsia in women with preeclampsia. The current study is a multicenter, randomized, controlled trial to compare the anti-seizure effect of parenteral MgSO4 versus oral labetalol in hypertensive pregnant women who are eligible for MgSO4 therapy. The primary outcome measure is eclampsia, and the secondary outcome measures include blood pressure control, and relevant antenatal, intrapartum, and postnatal maternal and fetal/neonatal parameters including adverse effects and complications. Inclusion criteria are deliberately broad in order to make the study clinically relevant. Hypertensive pregnant women, in whom the decision for delivery has been made, will be enrolled after written, informed consent. Patients will be randomized to receive MgSO4 therapy as given in their institution, versus oral labetalol (200mg/q6 hours), from enrollment in the study until 24 hours post delivery. There will be 4000 patients in each arm of the study and analysis will be by intention-to-treat. The study is powered to show both therapeutic superiority as well as clinical equivalence. This study has the potential to change the way preeclampsia is managed, and will represent a major advance in terms of the availability and safety of prophylactic therapy, especially in developing nations where MgSO4 is underutilized due to cost constraints.

Timeline

Start

2015-06

Primary completion

2017-01

Completion

2017-01

Publications

• Background Belfort MA, Anthony J, Saade GR, Allen JC Jr; Nimodipine Study Group. A comparison of magnesium sulfate and nimodipine for the prevention of eclampsia. N Engl J Med. 2003 Jan 23;348(4):304-11. doi: 10.1056/NEJMoa021180.
• Background Belfort MA. Is high cerebral perfusion pressure and cerebral flow predictive of impending seizures in preeclampsia? A case report. Hypertens Pregnancy. 2005;24(1):59-63. doi: 10.1081/PRG-45776.
• Background Belfort MA, Tooke-Miller C, Allen JC Jr, Dizon-Townson D, Varner MA. Labetalol decreases cerebral perfusion pressure without negatively affecting cerebral blood flow in hypertensive gravidas. Hypertens Pregnancy. 2002;21(3):185-97. doi: 10.1081/PRG-120015845.
• Background Belfort MA, Tooke-Miller C, Varner M, Saade G, Grunewald C, Nisell H, Herd JA. Evaluation of a noninvasive transcranial Doppler and blood pressure-based method for the assessment of cerebral perfusion pressure in pregnant women. Hypertens Pregnancy. 2000;19(3):331-40. doi: 10.1081/prg-100101995.
• Background Riskin-Mashiah S, Belfort MA. Cerebrovascular hemodynamics in chronic hypertensive pregnant women who later develop superimposed preeclampsia. J Soc Gynecol Investig. 2005 Jan;12(1):28-32. doi: 10.1016/j.jsgi.2004.08.002.
• Background Belfort MA, Varner MW, Dizon-Townson DS, Grunewald C, Nisell H. Cerebral perfusion pressure, and not cerebral blood flow, may be the critical determinant of intracranial injury in preeclampsia: a new hypothesis. Am J Obstet Gynecol. 2002 Sep;187(3):626-34. doi: 10.1067/mob.2002.125241.
• Background Belfort MA, Saade GR, Yared M, Grunewald C, Herd JA, Varner MA, Nisell H. Change in estimated cerebral perfusion pressure after treatment with nimodipine or magnesium sulfate in patients with preeclampsia. Am J Obstet Gynecol. 1999 Aug;181(2):402-7. doi: 10.1016/s0002-9378(99)70569-7.

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