As we age, changes in kidney function, liver function, metabolism, and balance make some common over-the-counter (OTC) medicines far more likely to cause side effects or dangerous drug interactions than they did decades earlier. Using OTC Sleep Aids Every NightDifficulty sleeping becomes more common after retirement, but many OTC sleep aids rely on diphenhydramine, the same antihistamine found in Benadryl. Ibuprofen and naproxen are among the most commonly used OTC medications in America. Forgetting to Mention OTC Medications at Medical AppointmentsMany patients bring a list of prescriptions to doctor visits but leave out vitamins, herbal supplements, antacids, allergy medications, and pain relievers. Signs an OTC Medication May Be Causing ProblemsWhen it comes to OTC medication safety, everyone should be aware of the symptoms to look out for.