In a new health policy statement, the U.S. Food and Drug Administration (FDA) and other major health organizations have called for improvements in the way medications are developed and tested in children with heart disease.

They called for drug trials to be more flexible so they can avoid enrollment problems and other barriers to perform research on children with heart disease. Additionally, they asked for better, more concrete data that can prove treatments are effective.

Getting accurate data on how medications affect children can be hard because, as patients, they're rapidly growing and developing, which requires constant adjustments in drug dosages. It’s also hard to collect enough patients for trials because cardiovascular disease at a young age is rare.

But the biggest hurdle by far is funding, according to Thomas Kimball, MD, medical director of the heart institute at Cincinnati Children’s Hospital Medical Center in Ohio. Typically, drug manufacturers focus on funding research for adult drugs since they are sold in much higher volumes, Kimball said.

With all the obstacles in place, the FDA prioritized addressing them and met with the American College of Cardiology, the American Heart Association and the American Academy of Pediatrics in 2014 to discuss sildanefil, which is branded Revatio.

“The meeting with FDA was the first of its kind,” said Craig Sable, MD, the lead author of the statement and the associate division chief of cardiology at Children’s National Health System in Washington, D.C.

In clinical trials on Revatio, data showed that high doses of the drug were killing children. At that point, the FDA issued a strong a warning against it in 2012, advising it not be given to children with pulmonary hypertension.“I understood why the FDA didn’t approve the drug for use in children, but I didn’t understand the strength of the warning,” said Dunbar Ivy, MD, lead author of the sildenafil trial and professor of medicine in pediatric cardiology at the University of Colorado School of Medicine in Aurora.