You’re pregnant and can’t sleep. Miserable, you ask your doctor what to take. “Diphenhydramine,” you’re told. It’s the active ingredient in sleep aids such as Benadryl, Unisom, Sominex, Exedrin PM and Tylenol PM. An antihistamine, it’s also an over-the-counter drug that pregnant women take when they have a cold or allergies.
“Why not? The FDA classified diphenhydramine as a “Category “B” drug in pregnancy, meaning that there’s no evidence of risk in humans.
Here’s why not. A study published this week in JAMA Internal Medicine found that the cumulative use of Benadryl and other similar nonprescription medications is linked with dementia and cognitive impairment in older people. This study is not the first to find a connection, but it’s the largest one to date. The researchers tracked nearly 3,500 people for seven years. Around 800 of them developed dementia by the end of the study, and those who used Benadryl were likelier to have cognitive impairment than those who did not.
In particular, the study estimated that people taking at least 4 mg/day of diphenhydramine for more than three years are at a greater risk of developing dementia. (The average dose of Benadryl for use as a sleep aid is 50 mg.)
The reason: this drug is an anticholinergic, which works by blocking the action of the neurotransmitter acetycholine. In the brain, acetylcholine is necessary for learning and memory.
Wait!, you might think. The study participants were seniors. The causal link isn’t proven. And the risk, if real, appears to be accumulative.
On the other hand, science has not studied the effects of these drugs on fetuses, infants, or children. Couldn’t the same anticholinergic effects disrupt a baby’s developing nervous system? What might it be doing to a fetus’s brain; the infrastructure of its neural pathways? Even a minor decrease in cognitive function would be alarming.
This study warrants a good, hard look at the effects of common anticholinergic drugs on the developing brains of fetuses, babies, and children. If I were a doctor, I would urge my pregnant and pediatric patients to seriously consider alternatives. Or take it only in emergencies. After all, we now know there’s a lot that we don’t know.
And if were pregnant again, I’d never take Benadryl or anything else with diphenhydramine. Not even if I were struck with insomnia and a killer cold, as I was last November and December in third trimester of my pregnancy. The fact that we now know that this drug may impair the elder brain but haven’t yet explored its effect on the young brain…. If I took it, I’d never be able to sleep.