Here’s a bit of history–the original Federal Food, Drug, and Cosmetic Act of 1938 made no clear-cut distinction between prescription and over-the-counter (OTC) drugs. That changed with the 1951 Durham-Humphrey amendments; it says that drugs that cannot be used safely without professional supervision must be dispensed only by prescription. All other drugs can be sold over the counter. A drug must be made available without a prescription if, by following the label, consumers can use it safely and effectively without health professional guidance.
When considering switching a prescription product to OTC, the key questions for FDA are whether consumers will be able to understand and follow label directions, whether patients can diagnose the condition themselves–or at least recognize the symptoms they want to treat–and whether routine medical examinations or laboratory tests are required for continued safe use of a drug.
No easy risk-benefit formula exists when determining whether a drug should be made available over the counter. We do a case-by-case review of each drug because each drug raises unique issues.