Durham-Humphrey Amendment

This amendment to the Food, Drug, and Cosmetic Act, also known as the Prescription Drug Amendment, was signed into law by President Harry S. Truman on October 26, 1951. This amendment was co-sponsored by former vice president and senator Hubert H. Humphrey Jr., who was a pharmacist in South Dakota before beginning his political career. The other sponsor of this amendment was Carl Durham, a pharmacist representing North Carolina in the House of Representatives.

The Durham-Humphrey Amendment, enacted in 1951, resolved the issues left open by the 1938 Act. It established two classes of drugs: Rx legend (prescription) and OTC (over the counter). Prior to the passage of this amendment, drug manufacturers were generally free to determine in which category their drug belonged. A subsection of this amendment granted the FDA the authority to categorize prescription drugs as those that are habit-forming, unsafe for use except under the supervision of a health care practitioner, and/or subject to the new drug application approval process.

This amendment provided the requirement for either a written prescription from a physician or an oral prescription from the physician that is immediately reduced to writing. Along with this, authorization of refills on prescriptions were made legal. Up until this point, prescriptions were treated like canceled checks and therefore after being filled were considered void. This refill provision made great sense when considering maintenance medications.

Additionally, under this amendment, a drug manufacturer can switch their product from Rx to OTC status by doing any one of the following:
 * 1) The drug manufacturer can request the switch by submitting a supplemental application.
 * 2) The drug manufacturer can petition the FDA for the switch
 * 3) And the primary mechanism for switching drugs to OTC is for the drug manufacturer to go through the OTC process, and a review board which the FDA would have to agree to.

If the FDA agrees, a final report switching from a prescription drug to OTC drug takes place.

The amendment also gave guidance as to what minimal information must be included on the prescription label:
 * name and address of the pharmacy,
 * serial number of the prescription,
 * date of its filling,
 * the name of the prescriber,
 * the name of the patient,
 * the directions for use, and
 * any applicable warning labels.