503A vs 503B

503A and 503B are the two federal regulatory pathways for compounding pharmacies, defined in sections 503A and 503B of the Federal Food, Drug, and Cosmetic Act.

503A pharmacies prepare compounded medications for individually identified patients based on a valid prescription. They are primarily regulated by state boards of pharmacy and follow USP standards. Most patient-facing compounded prescriptions come from 503A pharmacies.

503B outsourcing facilities are registered with the FDA and can prepare batches of compounded sterile medications without a patient-specific prescription, generally for healthcare facilities such as clinics and hospitals. 503B facilities are subject to FDA inspection and cGMP requirements.

Patients filling an individual prescription are almost always working with a 503A pharmacy. Healthcare facility buyers procuring office-use sterile compounded batches are typically working with a 503B outsourcing facility.