503B bulk drug substances list
Where a compounded drug parts company with an FDA-approved one, where 503A parts company with 503B, and which accreditation programs tell them apart.
What is 503B bulk drug substances list?
FDA's roster of active ingredients a 503B outsourcing facility is permitted to compound from once no shortage is on the books.
Semaglutide, tirzepatide and liraglutide are not on it. On April 30, 2026 FDA proposed keeping all three off, on the view that outsourcing facilities have no clinical need to make them from bulk; comments were taken until July 30, 2026, and by October 2026 FDA had not published a final decision. Until a drug is on the list or back on the shortage list, a 503B facility has no route to compound it from bulk.
Related reading: Which GLP-1s Can Be Compounded? The FDA Shortage and Bulks-List Rules
GLP Watchdog writes these definitions from FDA labels and peer-reviewed PubMed literature.
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