Magnesium Sulfate and Nimodipine for the Prevention of Eclampsia
Magnesium Sulfate and Nimodipine for the Prevention of Eclampsia
Abstract & Commentary
Synopsis: Magnesium sulfate is more effective than nimodipine for prophylaxis against seizures in women with severe preeclampsia.
Source: Belfort MA, et al. N Engl J Med. 2003;348: 304-311.
Through the years clinicians outside the country and nonobstetricians inside the country have challenged the concept of using magnesium sulfate for the prevention of eclampsia. However, each time it gets pitted against another agent in a randomized trial, magnesium sulfate wins out. 1-3
The latest multicentered trial published in the New England Journal of Medicine by Belfort and colleagues assessed the antiseizure ability in preeclamptics of magnesium sulfate compared with a calcium channel blocker nimodipine. The rationale for using the latter drug is that eclamptic seizures result from cerebral vasospasm and ischemia, and that nimodipine is a specific vasodilator of the cerebral circulation.
The study involved 1650 severe preeclamptic patients randomly assigned to being treated with intravenous magnesium sulfate vs nimodipine (60 mg q.4h. p.o.). Hypertension was controlled in both groups with hydralazine.
Twenty-one of 819 patients (2.6%) in the nimodipine group had seizures, compared with 7 of 831 (0.8%) in the magnesium sulfate group (P = 0.01). In effect, the chances of eclampsia were 3.2 times greater when using nimodipine. Most of the seizures occurred postpartum in the nimodipine group. Not surprisingly, the magnesium sulfate patients needed hydralazine more frequently to control blood pressure.
Comment by John C. Hobbins, MD
Magnesium sulfate has become a therapeutic staple for the American obstetrician, but in some areas in Asia, where preeclampsia is very common, Valium is the drug of choice for prevention of eclampsia. In some European countries, where there is an antimagnesium mentality, various anti-epileptic medications are used for seizure prophylaxis in preeclampsia, despite a large randomized trial from Dallas showing that magnesium sulfate fared better than Dilantin in preventing eclampsia.
Magnesium sulfate has many properties that are useful in severe preeclampsia. It has a modest antihypertensive effect, is an osmotic diuretic, and decreases uterine resistance thereby causing an increase in uterine blood flow. Now we find out that magnesium sulfate decreases cerebral perfusion pressure, an action that discourages seizure activity.
Interestingly, a very recent randomized, placebo-controlled trial from the prolific group in Memphis indicates that magnesium sulfate does not affect the progression of disease in mild preeclampsia.4
Lest we think that magnesium sulfate can do no wrong, we must remember that intravenous magnesium needs to be carefully watched and has uncomfortable side effects. In a previous OB/GYN Clinical Alert, we covered a study that suggested that there was a relationship between the dose used to prevent preterm labor and adverse neonatal outcome. For these reasons, we should keep in mind that not even a tried-and-true drug such as magnesium sulfate, like the condition we are treating, should not be taken lightly.
Dr. Hobbins is Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver.
References
1. Lucas NJ, et al. N Engl J Med. 1995;333:201-205.
2. Coomarasamy A, et al. Obstet Gynecol. 2001;98: 861-866.
3. Belfort MA, et al. Am J Obstet Gynecol. 1999;181: 402-407.
4. Livingston JC, et al. Obstet Gynecol. 2003;101: 217-220.
Magnesium sulfate is more effective than nimodipine for prophylaxis against seizures in women with severe preeclampsia.Subscribe Now for Access
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