Over-the-counter (OTC) medicines are drugs that can be purchased without a prescription. They treat various symptoms and conditions, including pain, coughs, colds, diarrhea, and heartburn. OTC medicines are regulated by the FDA and are available in pharmacies, grocery stores, and online. Examples include pain relievers like acetaminophen and ibuprofen, cough suppressants like dextromethorphan, and antihistamines like loratadine.