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Dextromethorphan and diphenhydramine, both over-the-counter drugs, are sold alone and in combination with other products as cough suppressants for children and adults. We have previously recommended dextromethorphan as a safe and effective cough suppressant for both children and adults. However, the weight of the evidence now suggests that neither dextromethophan nor diphenhydramine is any more effective than an inactive placebo syrup in suppressing a nighttime cough in children.
The study...
Dextromethorphan and diphenhydramine, both over-the-counter drugs, are sold alone and in combination with other products as cough suppressants for children and adults. We have previously recommended dextromethorphan as a safe and effective cough suppressant for both children and adults. However, the weight of the evidence now suggests that neither dextromethophan nor diphenhydramine is any more effective than an inactive placebo syrup in suppressing a nighttime cough in children.
The study tipping the balance for us to a DO NOT USE classification for these drugs was published in the July 2004 issue of the journal Pediatrics and was conducted by researchers from the Pennsylvania State College of Medicine, Hershey, Pennsylvania.
Sleep quality was used as the measure of effectiveness in the study for the two drugs and the placebo. The study involved 100 children with coughs and their parents, and used a five-question questionnaire to assess sleep quality for both children and their parents. The median age of the children was 4.5 years and their ages ranged from 2.0 years to 16.5 years. To be eligible to participate in the study, the children had to have an acute cough as a result of an upper respiratory tract infection.
The questionnaire was administered on two consecutive days. On the first day no medication had been given the previous night and on the second day it was administered after the drugs or the placebo had been given the previous night.
The study concluded that dextromethorphan and diphenhydramine were not superior to the placebo in providing nighttime symptomatic relief for children with a cough and sleep difficulty as a result of an upper respiratory tract infection. In addition, the use of these drugs did not result in improved sleep quality for the children’s parents. In other words, neither drug had any effect on the natural course of cough improvement over a 24-hour period.
Dr. Ian Paul, the study’s lead investigator, on July 6 was quoted on ABC News, saying that, “The kids that got the medicines in the study, they didn’t cough any less, they didn’t cough any less severely or sleep any better than the kids that got the sugar water.”
Older research on the value of these drugs as cough suppressants was conflicting. Recently, a type of statistical summary of multiple studies known as a meta-analysis published in the February 9, 2002 British Medical Journal concluded “Over the counter cough medicines for acute cough cannot be recommended because there is no good evidence for their effectiveness.”
The American Academy of Pediatrics’ Committee on Drugs has not supported the use of dextromethorphan or codeine primarily because there is a lack of proven benefit, and some potential for toxicity and overdose.
Even ineffective drugs have the potential to cause adverse effects. In usual doses, dextromethorphan has been associated with loss of muscle tone, severe allergic reactions and the proliferation of a type of cell called mast cells that may appear as a blister. Overdose of dextromethorphan may result in psychosis, mania, or hallucinations. Deaths have been reported from an overdose of this drug.
Diphenydramine is also commonly used as an antihistamine (for which it is effective) and shares the adverse effects of this family of drugs. These include drowsiness, occasional restlessness, nervousness, and insomnia in usual doses. Death can result from an overdose with diphenydramine.
Parents and health professionals have a strong urge to “do something” to ease symptoms in children even in a mild, self-limiting illness such as an upper respiratory tract infection. The lesson from this study is that it is sometimes better to do nothing because the medications have no therapeutic benefit, but do carry a known risk of potentially serious adverse reactions.
What You Can Do
You should not use dextromethorphan or diphenhydramine for cough suppression. Neither drug is effective and each has its own risks.
