Glossary
Also written 503B
Section 503B governs outsourcing facilities, which register with the FDA and may compound at scale rather than one prescription at a time. It is the route that made mass-produced compounded copies of shortage drugs possible, and closing it is what ended them.
The FDA proposed in April 2026 to exclude semaglutide and tirzepatide from the 503B bulks list, which closes the outsourcing-facility route for those molecules and leaves the narrow patient-specific route under section 503A as the lawful remainder.
Three molecules in this index are named in Category 2 under FDA's separate 503B policy for outsourcing facilities. That listing is recorded apart from each molecule's 503A position.