Children Remain Alert and Ready to Learn When Taking Over-the-Counter Antihistamines That Make Adults Drowsy

The over-the-counter antihistamine diphenhydramine, commonly sold under the trade name Benadryl, has such potent sedative effects in adults that it is marketed as a sleep aid as well as an antihistamine. But new research indicates that it has quite different effects in children. Neither diphenhydramine, nor the non-sedating prescription antihistamine loratadine, sold as Claritin, had any effect on children's alertness or ability to learn, according to a study done by scientists at National Jewish Medical and Research Center. The study appears in the May 2001 issue of The Journal of Pediatrics and reinforces a growing realization that children often respond quite differently from adults to the same drugs.

"Kids are not just small versions of adults. Their physiology is different," said Bruce Bender, PhD, head of pediatric behavioral health at National Jewish and lead author of the study. "What was learned in adult studies of antihistamines doesn't necessarily apply to children. You really have to do studies with kids." Numerous studies have shown that diphenhydramine significantly sedates adults and can impair their driving ability as much as alcohol. Several kinds of non-sedating prescription antihistamines have offered safer alternatives for adults with seasonal allergies. However, very little research has been done on the effect of antihistamines on children.

"This is the first study of this kind done in a school setting rather than a laboratory," said Dr. Bender. "We were trying to recreate the real world as much as possible, to see how the drugs might affect a child's ability to stay alert and to learn in school."

The National Jewish research team enrolled 63 children aged 8 to 10 years old in a simulated school for four days on three consecutive weekends. The students all had histories and positive skin tests for allergies but were not suffering allergies at the time of the test. In a double-blind setting the students were then given either a placebo, or children's recommended doses of diphenhydramine or loratadine twice a day during the first three simulated school days. No medications were given on the fourth day.

The study setting was designed to simulate a real school as much as possible. Students came to the Kunsberg School, an elementary school on the campus of National Jewish. Registered teachers in the Denver Public School system gave one-hour presentations on plant reproduction, and children read from an elementary school textbook on the same subject. Children also had school periods for art, physical education, classroom discussion, and a computer lab. They received caffeine-free breakfasts and lunches.

At the end of each school day, students were tested on the material they had learned, were given computerized reaction-time tests, and also reported how sleepy they felt. To the surprise of the researchers, children who had received either diphenhydramine or loratadine scored the same on the tests as did children who received placebos.

"The results were quite a surprise," said Dr. Bender. "Our hypothesis was that the group receiving diphenhydramine would score significantly lower. We thought the kids' reactions to the medications would be similar to those of adults."

Dr. Bender cautions that this one study does not settle the question about diphenhydramine, alertness, and learning. Two previous studies reported conflicting results. But he believes that it does raise significant doubts about the assumed effects of diphenhydramine on children. It also highlights the physiological differences between children and adults, and the need to study the effects of drugs in children before approving them for pediatric use.

The study was funded by a grant from Schering-Plough.