During pregnancy, many women turn to over-the-counter medications to reduce symptoms like morning sickness, back pain or headaches. Often, these discomforts start early in the pregnancy. But doctors suggest avoiding any drug when possible during the first trimester of pregnancy, because it is when most of the vital organs develop in a fetus. Most health professionals consider Benadryl safe throughout pregnancy, though, especially to reduce morning sickness during the crucial first trimester.
Diphenhydramine is the main ingredient in Benadryl, an over-the-counter antihistamine product that is used to treat allergies. Diphenhydramine is also the main ingredient in many over-the-counter sleep aid products, because its primary side effect is drowsiness. In addition, diphenhydramine is approved by the Food and Drug Administration to block nausea and vomiting of motion sickness. The drug is used in a similar way to prevent morning sickness in pregnant women. Doses of 25 and 50 mg are used in adults. Benadryl works for four to six hours, and its effect is greatest within the first hour.
Benadryl Use in Pregnancy
According to a 2005 study published in the American Journal of Obstetrics and Gynecology, Benadryl use by pregnant women increased from 1976 to 2004. The drug is in pregnancy category B, which means that studies in animals at five times the human dose have not shown harm to fetuses but that no studies have been done in women to confirm safety. Therefore, Benadryl can be used when necessary during pregnancy.
Benadryl is an old enough drug that its effects and side effects are well known to doctors, but there are not many studies about the effect of Benadryl in pregnant women. In 2009, SM Gilboa and other researchers reported birth defects associated with many antihistamines, including Benadryl and newer drug options. Of the 24 defects, primarily non-heart related, that occurred, Benadryl was associated with eight. This did not support a direct connection between the antihistamine and defects, so additional studies could support or refute a connection.
Although Benadryl use during the first trimester for morning sickness has not been studied extensively, the drug has been compared to ginger, which is a natural remedy for nausea and vomiting. In a 2007 Thai study, ginger and Benadryl successfully reduced nausea and vomiting of morning sickness, but only Benadryl was associated with excessive sleepiness.
In the 1970s, Bendectin, which contained the antihistamine doxylamine, was marketed to women for morning sickness. Post-marketing reports suggested that doxylamine caused limb-related birth defects in high numbers, and Bendectin was removed from the market. Although Benadryl is in the same class of antihistamines as doxylamine, no studies or individual reports to the Food and Drug Administration support the same type of large-scale defects with Benadryl use.