Q. Do over-the-counter, nonprescription sleep aids work?

A. OTC sleep aids contain an antihistamine (e.g, diphenhydramine) as the active ingredient. As mentioned above, the NIH report (PDF) concluded that there is no systematic evidence for efficacy and there are significant concerns about risks of antihistamines used as a sleep aid. Possible side effects include daytime sedation, diminished cognitive function, confusion, dry mouth, blurred vision, urinary retention, and constipation. All of these are more likely in the elderly.

Read other Frequently Asked Questions about medications.