FDCA and Federal Prescription Requirements
The statutory frame
The FDCA of 1938, as amended by the Durham-Humphrey Amendments of 1951, created the prescription/OTC divide. A drug not safe for self-medication without professional supervision carries the 'Rx only' legend and may be dispensed only on a prescription of a practitioner licensed by law to administer it. Marketing approval runs through an NDA or ANDA; the DESI review and the OTC monograph are separate pathways. Enforcement rides on two hooks: adulteration (how the product is made or held) and misbranding (how it is labeled, advertised, or dispensed). Misbranding reaches pharmacy practice, not just manufacturers.
Where federal law stops
Federal law generally does not dictate what a prescription must contain, how long it remains valid, or how many refills a non-controlled legend drug may carry - those are state questions answered by the Board of Pharmacy. What federal law does reach: Medicaid written-prescription tamper-resistance (a pad with three security features, or electronic transmission), the Prescription Drug Marketing Act (no resale or sample diversion by non-registrants, no reimportation), child-resistant packaging under the PPPA, and mandated patient information such as Medication Guides, patient package inserts, and REMS elements.
Traps
A valid prescription need not be written; most legend drugs may be dispensed on an oral order unless state law or the prescriber says otherwise. Off-label prescribing is lawful and often the standard of care; off-label promotion by a manufacturer is not. A prescription missing a quantity or directions is not automatically void - know what the pharmacist may supply or must clarify.
Rule of thumb: bucket every prescription question into three parts - who may authorize it (state license, plus DEA registration if controlled), what it must contain (state), and how long it lives (state; CSA for controlled substances).