February 15, 2001
Exposure during pregnancy to DM, a main ingredient in cough syrup, does not increase the risk of birth defects
Researchers at The Hospital for Sick Children have concluded that exposure during pregnancy to Dextromethorphan (DM), an active ingredient present in a variety of cough and cold remedies does not increase the chances of major birth defects. Recently, data generated from a study in chick embryos suggested that pregnant women should not use this drug because of the risk of birth defects.
The Motherisk study, published in the February issue of CHEST, demonstrates that the use of DM during pregnancy does not increase the rates of major malformations above the expected baseline rate of one to three per cent.
“The recent study in chick embryos concluded that women should not use DM during pregnancy. The data had very limited applicability to humans but received wide publicity and caused high levels of anxiety among pregnant women and their health care professionals,” said Adrienne Einarson, the study’s lead author and the assistant director of the Motherisk program at The Hospital for Sick Children (SickKids).
“The data collected in this study indicates that DM is probably safe to use during pregnancy. The outcome of the study correlates with other previous studies on the use of DM during pregnancy, where there was no increase in major malformations above the one to three per cent possible in any pregnancy, and no increase in the relative risk of any specific malformation.”
Dextromethorphan (DM), is the d-isomer of the codeine analog levorphanol, an antitussive which is the active ingredient in a variety of over-the-counter cough and cold medications. It is a synthetic, non-narcotic, centrally acting cough suppressant, which is available either alone (as lozenges or oral solution) or in combination with a large number of other compounds used for upper respiratory tract infections.
This study, led by researchers in SickKids’ Motherisk program, looked at pregnancy outcome in 184 women who had used DM during pregnancy. The women in the study were counselled by the Motherisk program between 1995 and 1998. Each woman exposed to DM was paired in the study to another pregnant woman who also had an upper respiratory infection and had inquired about the safety of DM, but subsequently did not use it. Factors such as smoking, alcohol intake, age, and stage of pregnancy were taken into consideration.
The primary outcome of interest was the rates of major malformations. Major malformations are defined by the presence of any anomaly that has an adverse effect on either the function or the social acceptability of the individual. Secondary outcomes included spontaneous or therapeutic abortions, live birth or still birth, minor anomalies, and birth weight.
The outcome of 184 pregnancies exposed to DM, of which 128 occurred in the first trimester of pregnancy, report a 2.3 per cent rate of major malformations of women who used DM in the first trimester. In the control group, there was a 2.2 per cent rate of major malformations. These results suggest that the use of DM in pregnancy does not pose a risk to the fetus, although because of its size this study was unable to rule out an increase risk for rare malformations.
“The results of this study confirm that using DM in cough medicine during pregnancy, should not cause women and their health professionals undue alarm,” says Dr. Gideon Koren, the study’s principal investigator, director of Motherisk, and a professor of Paediactrics, Pharmacology, and Medicine and Medical Genetics at the University of Toronto. “The rate of birth defects documented in this study indicate that the risk of malformations is no greater than in the normal population.”
The Hospital for Sick Children is a health care, teaching and research centre dedicated exclusively to children; affiliated with the University of Toronto. For more information, please visit the SickKids website at http://www.sickkids.ca/.
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