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Treatment for premature labor reevaluated.

The drug ritodrine, widely used to prevent premature delivery, does not work in many cases, according to a large-scale study reported by Canadian researchers in the July 30 NEW ENGLAND JOURNAL OF MEDICINE.

Experts call for reduction of ritodrine treatments in light of potentially serious maternal side effects. "These results should greatly influence the treatment of preterm labor all over the world," concludes an editorial in the same journal by Kenneth J. Leveno and E Gary Cunningham, obstetricians at the University of Texas Southwestern Medical Center at Dallas.

Given to an estimated 100,000 U.S. women each year, ritodrine relaxes the muscles of the uterus and thus may temporarily halt preterm labor, says Lereno. The first randomized clinical trials of this drug took place in the early 1970s, but it was not approved for use in the United States until 1980. Developed for obstetrical use, ritodrine is the only drug specifically approved for treatment of preterm labor by the Food and Drug Administration.

But controversy has long surrounded its use, says Leveno, who believes the new findings confirm that ritodrine has few long-term benefits. In the largest ritodrine test yet conducted, researchers at six Canadian hospitals studied 708 women in danger of delivering their babies prematurely and followed 246 of their infants for 18 months. Each mother received randomly assigned treatment with either ritodrine or a placebo. Infants' gestational ages at the initiation of the study ranged from 20 to 35 weeks.

While ritodrine lowered the proportion of women who delivered within 24 to 48 hours after administration, it had no significant beneficial effects on the overall rates of premature delivery, low birth-weight, or infant mortality, the team reports. In addition, mothers given ritodrine showed an increase in serious side effects such as chest pain, irregular heart rhythms, and fluid-filled lungs.

Although none of the women in the Canadian study died, some maternal deaths have been associated with ritodrine use, according to Leveno and Cunningham. The Dallas obstetricians call for FDA to "reappraise the vanishingly small neonatal benefits in light of the substantial maternal risks of ritodrine."

The drug may often be given unnecessarily, since. "most of the women who threaten to deliver prematurely do not:' Leveno adds. "The Canadian study shows very clearly that not giving any medicine does not mean that the patient delivers prematurely"

Although ritodrine "shouldn't be used in the majority of cases where we do use it, there is still a place for it," contends study coauthor Sidney B. Effer, an obstetrician at the University of British Columbia in Vancouver.

Effer emphasizes that ritodrine can help to delay delivery until patients can be transferred to a hospital with a neonatal intensive care facility, In addition, the study indicates that for a crucial time in pregnancy - between 24 and 27 weeks, while the infant's lungs are developing ritodrine may achieve a 7.2 percent decline in infant mortality Effer and his coworkers conclude that ritodrine may be beneficial if used before a gestational age of 28 weeks or in conjunction with drug therapies designed to stimulate the growth of the baby's lungs.

While this study highlights the need for new treatments, "there is still a lot of hope" for today's premature babies, says Leveno, who notes that overall infant mortality in the study was less than 6.5 percent for both the ritodrine and the placebo groups.

The FDA plans an open advisory committee meeting on Oct. 20 to reassess the maternal risks and neonatal benefits of ritodrine and other uterine-relaxing agents. - K. Hoppe
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Title Annotation:ritodrine may cause serious side effects
Author:Hoppe, Kathryn
Publication:Science News
Article Type:Brief Article
Date:Aug 8, 1992
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