Pinning this for the FAQ. One more distinction worth noting:
503A pharmacies are required to compound from bulk drug substances that are either:
- Components of FDA-approved drugs, OR
- On the FDA's "bulks list" (positive list under 503A)
503B facilities can compound from bulk drug substances that appear on the FDA's "clinical need" list (though this list is still being developed).
Both semaglutide and tirzepatide base are currently available as bulk drug substances because of the ongoing shortage designations. If/when those shortage designations end, the legal landscape for compounding these drugs could change dramatically. The FDA has signaled that they may give compounders a wind-down period, but nothing is guaranteed.
This is the elephant in the room that every compounder and patient should be thinking about.
Last edited: May 20, 2026 at 3:41 PM