Parents assume that when a pediatrician prescribes a drug for their child, that drug has been tested and proven safe and effective. If only it were so. Only half of the medicines doctors prescribe to patients 18 and younger have been through the same rigorous trials as those drugs prescribed to adults. The other half are given off-label—that is, in circumstances for which they were never properly vetted, putting children at risk for overdoses, side effects and long-term health problems. For newborns, that fraction rises to 90 percent. In July the U.S. Congress gave the Food and Drug Administration new authority to compel companies to test their products for kids. The law should improve the situation, but it has worrying gaps.

As biologists have come to appreciate, drug metabolism is one of the many ways in which kids are not just small adults. When doctors downsize an adult dosage to suit a child's weight or body surface area, a drug can prove ineffective or harmful. Infants have immature livers and kidneys, so even a seemingly small dose of medicine can build up quickly in their bodies. As children mature, their organs can develop faster than their body size, so they need to take disproportionately more of the drug. For example, some recent pediatric clinical trials have found that the asthma medication albuterol does not work for children younger than four when taken through an inhaler. The seizure drug gabapentin (Neurontin) requires higher-than-expected doses for children under five.

The reason that drug companies neglect their youngest customers is simple. Children make up a small fraction of the world's drug recipients, so developing and testing new medicines for them is rarely worthwhile from a business perspective. Pediatric trials are especially expensive and complex, in part because of the difficulty of finding enough patients to enroll in them.

Congress began to address the issue in 1997, and its latest legislation, known as the FDA Safety and Innovation Act, strengthens those earlier efforts. The law requires pediatric studies for certain drugs and provides incentives to test others, such as a six-month patent extension. In addition, the law requires better advance planning of pediatric studies, improves the transparency of data and makes special provisions for newborns. The American Academy of Pediatrics praised the law: “The bill ensures that children will have a permanent seat at the table for drug research and development.”

Still, the law leaves many children vulnerable. It does little for youngsters with cancer, who rely disproportionately on undocumented drugs. Earlier this year Genentech won FDA approval for the skin cancer drug vismodegib, which intervenes in the same molecular process thought to be involved in a childhood brain tumor, yet the company was under no obligation to test the drug in younger patients. Congress needs to close this loophole, and in the meantime the FDA should continue to work closely with pharmaceutical companies and pediatric oncologists to find new ways of identifying and testing promising cancer medicines in children.

Another problem is that doctors are worryingly in the dark about the long-term health effects of pediatric drugs. Young people take medications for asthma, diabetes, arthritis and many other chronic conditions, yet rarely are side effects recorded and followed up on. In its February report “Safe and Effective Medicines for Children,” the Institute of Medicine recommended that the FDA make greater use of its authority to require long-term safety studies when it approves a product for pediatric use.

That said, the FDA Safety and Innovation Act is an important achievement. Children's medications are safer now than at any time in history, and many doctors and children's health advocates are so elated by the act's passage that they are reluctant to talk about what still needs to be done. But now is not the time to let up on our drive to make drugs safe for all our citizens. We hope this legislative victory will breed even more success.

Comment on this article at