Cough Medicines No Better Than Non-medicated Placebo Syrup For Children's Coughs

"Consumers spend billions of dollars each year on over-the-counter medications for cough," said Ian Paul, M.D., assistant professor of pediatrics, Penn State Children's Hospital, Penn State Milton S. Hershey Medical Center. "Our study showed that the two ingredients used in most over-the-counter medications were no better than a placebo, non-medicated syrup, in providing nighttime relief for children with cough and sleep difficulty as a result of upper respiratory infection."

The study, titled "Effect of Dextromethorphan, Diphenhydramine, and Placebo on Nocturnal Cough and Sleep Quality for Coughing Children and Their Parents," was published in the July 2004 issue of Pediatrics.

From June 2002 to May 2003, study volunteers ages two to 18 were recruited from patients with upper respiratory infections at two practices affiliated with Penn State Hershey Medical Center. Once consent was obtained from parents, parents were asked to answer questions about their children's conditions, such as cough severity, cough frequency, and the effect of the cough on sleep, using a seven-point symptom severity scale. Symptoms, as reported from the parents, had to reach a certain threshold for children to be admitted to the study. Then, each child was randomly assigned to receive dextromethorphan (often abbreviated as "DM"), diphenhydramine (an over-the-counter antihistamine) or placebo. Neither the physician nor parent knew which of the three the child would take.

Parents were instructed to give the medication to the child 30 minutes before bedtime. The next day, a second survey was administered to parents asking the same questions as the day before. (The study was approved by the Institutional Review Board under federal regulations at Penn State Milton S. Hershey Medical Center.)

Of the 100 children with upper respiratory infections included in the study, 33 patients received dextromethorphan, 33 received diphenhydramine and 34 received placebo. Patients were ill an average of 4.21 days before participation in the study. The symptom scores from the night before treatment were compared to those after treatment.

"All three groups, including the non-medicated syrup group, showed dramatic improvement, with scores for cough frequency, impact on child and parent sleep, bothersome nature of cough, and severity of cough scoring lower," Paul said. "Neither dextromethorphan nor diphenhydramine was superior to placebo for any outcomes studied in this trial."

Not only was there no significant improvement for the children who took cough medicines with the active ingredients, but in the cough frequency category, those who received placebo reported a 2.24-point improvement in cough frequency, whereas the parents of those who took the medicines with active ingredients reported only a 1.97-point improvement.

One unique aspect of this study was that it considered whether parents' sleep was significantly better when their child took a cough medicine.

"Parents often look particularly hard for ways to calm their child's cough at night because parents, too, need sleep to get through their daytime activities," Paul said. "Our study specifically evaluated this variable and showed that, not only did children's sleep not improve, but parents' sleep didn't improve when their child received active medication versus placebo."

When results for all five outcomes were combined, there was no significant difference between treatments. The children in the diphenhydramine group improved an average of 11.79 points compared with 10.06 for dextromethorphan and 10.85 for placebo. In addition, children's sleep did not improve.

"There was a significant improvement for all symptoms over the previous night, which should reassure clinicians and parents that, regardless of treatment, the natural history of an upper respiratory infection favors resolution of symptoms with time," Paul said. "The desire to ease symptoms is strong for both parents and clinicians. This study, however, questions whether over-the-counter medications have a place in the treatment of these illnesses for children."

Paul suggests that clinicians should consider these findings, the potential for adverse effects from using them, and the cumulative costs of the drugs before recommending them to families. He also notes that dextromethorphan has become a drug of abuse among adolescents.

In addition to Paul, other study team members were: Katharine E. Yoder, Kathryn E. Crowell, M.D., Michele L. Schaffer, Ph.D., Heidi S. McMillan, M.D., Lisa C. Carlson, M.D., Deborah A. Dilworth, R.N., and Cheston M. Berlin, M.D. This study was funded, in part, by the Children's Miracle Network and used the resources of the Penn State General Clinical Research Center at Penn State Milton S. Hershey Medical Center.