Glossary
Also written 503A
Section 503A of the Federal Food, Drug, and Cosmetic Act is the provision under which a licensed pharmacy may compound a drug for an individual patient who holds a valid prescription. It is the route by which a molecule with no approved product can nonetheless reach a patient lawfully, and it is the route almost every question on this index eventually turns on.
The permission is not open-ended. A pharmacy compounding from a bulk substance may draw only on substances the FDA has nominated to its interim list and sorted as compoundable while review continues, and it may not compound what is essentially a copy of a commercially available approved drug unless a prescriber documents a clinical difference for an individual patient. The FDA has rejected price as such a difference.