THURSDAY, Jan. 23, 2003 (HealthDayNews) -- For women with preeclampsia, a dangerous complication of pregnancy, the drug magnesium sulfate works better than a drug designed to dilate blood vessels in the brain, researchers say after comparing the two.
The finding is also leading researchers to rethink what causes preeclampsia in the first place.
While magnesium sulfate is the accepted treatment for preeclampsia, Dr. Michael A. Belfort and his colleagues decided to compare it with nimodipine (brand name Nimotop), a drug used to open brain blood vessels, because they thought it might work better and be more convenient.
Constricted blood vessels in the brain are thought to lead to the condition. Magnesium sulfate is usually administered intravenously, while nimodipine can be given orally when a woman has preeclampsia, a condition marked by high blood pressure, sudden weight gain and protein in the urine. Left untreated, preeclampsia can progress to eclampsia, marked by seizures, agitation and unconsciousness.
"The hypothesis that we set out to test was that nimodipine would prevent more seizures than magnesium sulfate," says Belfort, a professor of obstetrics and gynecology at the University of Utah and lead author of the study. It appears in the Jan. 23 issue of The New England Journal of Medicine.
However, magnesium sulfate was better at preventing seizures, the team reports. Even more important than that finding, Belfort says, is that the result calls into question whether preeclampsia is really caused, as experts have believed, by the brain's blood vessels constricting and going into spasm.
"From my perspective, the study's most significant contribution is that it sheds light on the pathophysiology of eclampsia," Belfort says. If it is truly caused by constricted circulation in the brain, the drug to open brain blood vessels should have worked better than the magnesium sulfate.
Based on the study results, "we are now able to say with reasonable certainty that the most common form of eclampsia is probably not caused by vasospasm or ischemia [reduced blood flow] and is much more likely to be the result of overperfusion [too much blood] than underperfusion," Belfort says./p>
In the study, Belfort's team randomly assigned 1,650 women with severe preeclampsia to receive either 60 milligrams of nimodipine every four hours or intravenous magnesium sulfate, continuing until a day after giving birth. While 2.6 percent of the nimodipine-treated women had seizures, only 0.8 percent of those on magnesium sulfate did.
The study was funded in part by Bayer Corp., which makes Nimotop.
Worldwide, preeclampsia and eclampsia occur in about 3 percent of pregnant women and are blamed for 12 percent of pregnancy-related deaths, according to the World Health Organization. About 2 percent of women with preeclampsia develop eclampsia.
Last year, a study published in The Lancet involving more than 10,000 pregnant women from 33 countries found that women with preeclampsia who received magnesium sulfate had a 58 percent lower risk of eclampsia than those who received inactive placebo. Magnesium sulfate was so superior to placebo that the study was halted early.
Another expert, Dr. Baha Sibai, agrees the contribution of the most recent study is the doubt it sheds on the traditional view of how and why eclampsia develops.
"What this study shows is that magnesium sulfate is better than nimodipine at preventing seizures, so it is unlikely it works by relaxing the blood vessels in the brain," says Sibai, chairman of the department of obstetrics and gynecology at the University of Cincinnati.
"Exactly how magnesium sulfate works [to prevent the seizures of eclampsia] is not known," he says. "But we still believe it's the best drug."
More information
For more information on preeclampsia and eclampsia, try the National Library of Medicine or the Preeclampsia Foundation.
