Nonprescription Medicines and Products - Topic Overview. A nonprescription medicine-sometimes called an over-the-counter, or OTC, medicine-is any drug that you can buy without a doctor's prescription. But don't assume that all nonprescription drugs are safe for you. These drugs can interact with other medicines and can sometimes cause serious health problems. And if you take more than the normal or recommended amount, overdose may occur. Some medicines should only be used by adults or older children.