The study found the risk of heart failure dropped significantly for children having coronary surgery after they took milrinone, originally developed for adults. The results are reported the Feb. 25 issue of Circulation.
"The drug was never tested, but it was used on children after they got sick. Now it can be used to prevent sickness. And we've been able to show that it's safe," says study co-author Dr. Gil Wernovsky, director of the cardiac intensive care unit at the Children's Hospital of Philadelphia.
Besides being the largest ever study of its kind, the trial illustrates the improving drug testing standards for children.
"Many drugs used for children have never been thoroughly tested in children, and we can't assume that children are just small adults," Wernovsky says. "There were a number of people who didn't want to use the drug because they were concerned about the safety in young babies. I think this will change a lot of minds."
About one in 100 babies are born with cardiac disease, and roughly one-third of those require heart surgery. In this trial, 238 patients participated at hospitals around the United States and Canada.
Katherine Curro, coordinator of cardiology research at the Children's Hospital of Wisconsin in Milwaukee, didn't take part in the study, but she was eagerly tracking the results.
"We use [milrinone] pretty routinely here," she says. "It's important to have studies back up these drugs."
Milrinone is a vasodilator, which lets blood vessels relax, thereby increasing blood flow. Included in that class of drugs is Viagra, which is also being tested on children with heart problems, Curro says.
Although there are ethical questions surrounding drug trials on children -- such as consent and health risks -- researchers say they are necessary. Once a drug passes trials, it's much easier for hospitals to use it with confidence and for families to receive insurance reimbursement for prescriptions, she says.
In the late 1990s, the U.S. Food and Drug Administration extended patent rights for six months for drugs that had had been tested on children, Wernovsky says, in an effort to urge more drug companies to test their medications on the youngest patients.
"It's a financial benefit for industry and it's a medical benefit for children," he says.
In this case, the trial was sponsored by Sanofi-Syntholabo Inc., which manufactures milrinone.
"It's a partnership with industry," Wernovsky says, saying it didn't damage the credibility of the study.
The patients were randomly divided into three groups: one receiving a low dose of milrinone, one receiving a high dose, and one receiving a placebo. Following surgery, the high-dose group was 55 percent less likely than the placebo group to suffer from a dangerous condition marked by low blood pressure and high heart rate, he says.
Side effects of milrinone reported in adults include low blood pressure, blood platelet abnormalities and irregular heart rhythms. In this trial, those effects appeared infrequently, the researchers say.