Rat Study: Labor Drug Might Affect Offspring Brain
Author: Merritt McKinney
Newborn rats given the drug terbutaline experienced more extensive brain damage when they were later exposed to a chemical often used in pesticides, researchers report.
Although the study was conducted in animals not people, the findings may help explain the reported increased risk of psychiatric and learning disorders in children who were exposed to terbutaline in the womb, according to a report in the March issue of the journal Toxicology and Applied Pharmacology.
Using drugs for preterm labor "comes at a cost: potential increase in the incidence of brain damage and associated cognitive and psychiatric problems later in life," said Dr. Theodore A. Slotkin, a pharmacologist at Duke University Medical Center in Durham, North Carolina.
Slotkin told Reuters Health the animal study suggests that children exposed to terbutaline in the womb may become especially sensitive to pesticides and other chemicals.
These children could be vulnerable to levels of chemicals that are otherwise "safe" for everyone else, he added.
Terbutaline helps stop premature labor by relaxing smooth muscles, which interferes with the contractions of the uterus.
According to Slotkin, for several years the American College of Obstetricians and Gynecologists has not endorsed the prolonged use of terbutaline to control preterm labor, and the drug's maker also advises against this practice.
"Nevertheless, many obstetricians continue to prescribe terbutaline or related drugs for long-term administration in pregnancy," he said.
"Our studies show that there are significant liabilities in doing so, and that the risk-benefit comparisons need to be reevaluated," he said.
In the rat study, Slotkin and his colleagues examined the effects of terbutaline and an insecticide called chlorpyrifos, which is known to have harmful neurological effects.
The Food and Drug Administration began gradually restricting the home use of chlorpyrifos in 2000, but it is still widely used in agriculture. People can be exposed to chlorpyrifos residues on produce.
Baby rats were exposed to terbutaline alone, chlorpyrifos alone or terbutaline followed by chlorpyrifos. A group of "control" rats were not exposed to either chemical.
When given alone, each chemical caused long-lasting changes in the development of brain cells, the researchers report.
What's more, terbutaline seemed to make the brain more sensitive to the effect of chlorpyrifos. As shown in rats that received both chemicals, the effect of the combined exposure was greater than the sum of the individual exposures.
More research is needed to determine the human impact of long-term terbutaline during pregnancy, according to Slotkin.
Children whose mothers were given terbutaline should be carefully evaluated for possible effects on intellectual and psychological development, he said. Future studies should also monitor the long-term effects of the drug on children's exposure to chemicals in the environment, according to the Duke researcher.