Popular antihistamine used to help young children sleep is ineffective

Although about half of pediatricians recommend that children under age 2 can be given diphenhydramine to help them sleep, the first study to look at effectiveness of the agent in children who are that young found no benefit.

In fact, the national study, conducted by researchers from Georgetown University Medical Center and published in the July issue of Archives of Pediatrics & Adolescent Medicine, found that the drug appeared to perform worse than a placebo agent. Only 1 out of 22 children showed improvement in sleeping after using diphenhydramine compared to 3 in 22 children who used a placebo. The drug, an antihistamine, is available over-the-counter in generic forms or as the name-brand drug, Benadryl..

Because of diphenhydramine's obvious lack of effectiveness, the clinical trial's Data Safety Monitoring Board shut down the study early, says lead author, Dan Merenstein, M.D., an assistant professor in the Department of Family Medicine at Georgetown.

"This is a small study, but one with big implications, because it is looking at the effectiveness of a widely used drug that has not been examined for infant and toddler use," says Merenstein. Half of pediatricians recommend use of diphenhydramine, according to surveys, and many child-rearing books offer the same advice, "but because the drug works as a sleep aide for some adults, we pretend it works for everyone," he says.

Merenstein cautions that a larger study is needed to definitively prove that diphenhydramine doesn't work as thought in young children, but adds, "At this point I would advise parents to think about different methods to help a child sleep," Merenstein says.

Researchers at Johns Hopkins University, Virginia Fairfax University, and the University of Hawaii worked with Merenstein on the study, which he conducted at Johns Hopkins before coming to Georgetown.

The clinical trial, known as TIRED (Trial of Infant Response to Diphenhydramine), enrolled 44 children, age 6-15 months, with the participation of their parents, and followed the families for six weeks. During this time, parents kept diaries to record the sleep habits of their children throughout the night. Treatment with a placebo agent or diphenhydramine occurred during one week, and the days before and after treatment were recorded for comparison purposes. The study was blinded in that neither researchers nor parents knew which children received which treatment.

The investigators had hypothesized that, based on the sedative properties of diphenhydramine in adults, treated children would be more likely to fall asleep without any other help from their parents, and that doing so would lead them to associate the crib with sleep and comfort, helping them to fall back asleep if they woke up.

But Merenstein says the results were surprising. Diphenhydramine use was no more effective than a placebo in reducing nighttime awakening, "or improving overall parental happiness with sleep for infants," he says.

Merenstein also notes that while it is generally reported about 7 percent of diphenhydramine users become "hyperactive," and so have increased sleep problems, only one child showed some evidence of hyperactivity. Still, he says, "it is possible that diphenhydramine caused low-level hyperactivity in children, negating the sleep benefits seen in some adults, but we really don't know why it didn't work."

"The bottom line here is that parents and pediatricians should rely on evidence-based medicine and not on leaps of logic that border on folklore," Merenstein says.