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.
Definition
The FDA list of active ingredients a 503B outsourcing facility may compound from when there is no approved drug shortage. On 30 April 2026 FDA proposed excluding semaglutide, tirzepatide and liraglutide from it — which, if finalized, closes the remaining lawful route for compounding GLP-1s at scale.
Which GLP-1s can be compounded →
GLP Watchdog writes these definitions from FDA labels and peer-reviewed PubMed literature. Not one of them is an AI-generated summary.
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