Antihistamines like diphenhydramine — the active ingredient in Benadryl, Tylenol PM and many cold medicines — are prescribed and sold over the counter to combat allergic reactions, dry up congestion and aid sleep.
While these drugs are useful, they also leave users feeling confused, sleepy and dizzy. This much is apparent from the inside sticker on a bottle of Benadryl tablets, which warns that “drowsiness may occur” and to “be careful when driving a motor vehicle.”
However, another, longer-term risk is absent from the warning label. A significant body of research has shown that diphenhydramine and other similar drugs increase the risk of developing Alzheimer's disease and other types of dementia.
What Are Anticholinergic Drugs?
Among pharmacologists, the class of medicines that Benadryl belongs to are known as anticholinergic drugs. These compounds suppress the activity of a neurotransmitter called acetylcholine, which is involved in memory and cognition, as well as muscle function elsewhere in the body. Aside from antihistamines, other anticholinergics include antidepressants and medications used to treat an overactive bladder.
