In brief

More on sleeping pills

We have received several letters asking about over-the-counter (OTC) medications like Tylenol PM that combine a pain reliever and a sleep aid. Several people said the pills helped them sleep and wanted to know if it was a good idea to keep on taking them.

The sleep-inducing ingredient in Tylenol PM is diphenhydramine, an antihistamine. People take antihistamines for hay fever or cold symptoms, but doctors have known for a long time that they also make people drowsy. Other nighttime pain relievers (Alka-Seltzer PM, Excedrin PM) contain diphenhydramine, and it's the only active ingredient in OTC sleeping pills like Sominex and Simply Sleep. Sominex and the allergy-relief version of Benadryl have exactly the same active ingredient: 25 milligrams of diphenhydramine.