This one has a reasonably settled answer, so here it is. The shortage clause is the answer to the second question and it is a subtraction rather than an addition. Both exemptions forbid compounding something that is essentially a copy of a commercially available approved product. A product FDA has listed as in shortage is not treated as commercially available, so listing removed the objection that otherwise blocked compounding. It never created a permission; it withdrew a prohibition, which is why it evaporated the moment the supply fact changed.
Two pharmacies quoted me last year, one describing itself as 503A and one as 503B, and I assumed 503B just meant bigger until both stopped within weeks of each other.
What would genuinely help is knowing what actually distinguishes 503A from 503B, in terms of what each may make and from what starting material.
Not looking for reassurance. Looking for the part I have got wrong.
Dr.GutHealth said:The shortage clause is the answer to the second question and it is a subtraction rather than an addition.
Agreed, and the enforcement dates were staggered by category — 503A first, 503B a few weeks later — because outsourcing facilities have manufactured inventory and clinic contracts to unwind while a 503A makes to order.
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Shop Reference StandardsPeptideChemSF said:Two pharmacies quoted me last year, one describing itself as 503A and one as 503B, and I assumed 503B just meant bigger until both stopped within…
Same position here, arrived at the long way round. They are two different exemptions from the same federal requirements and they buy different things. A 503A pharmacy is regulated primarily by the state board, needs a patient-specific prescription, is exempt from CGMP, and may use a bulk substance that has a USP monograph, is a component of an approved drug, or appears on the 503A bulks list — three independent doorways. A 503B outsourcing facility registers with the FDA, is inspected on a risk basis, must comply with CGMP, may compound for office stock without a patient-specific prescription, and has one doorway to a permitted bulk substance: the 503B bulks list, or the drug shortage list.
If somebody has the primary source to hand I would rather cite it than paraphrase it.
Adding the clinical framing, because it changes how the question reads.
Regarding compounded supply compounding legality: compounding pharmacies can legally produce semaglutide and tirzepatide while these drugs remain on the FDA shortage list. If/when the shortage resolves, the legal landscape may change.
Stay informed. The FDA shortage list is updated regularly. Current status as of my last check: semaglutide still in shortage, tirzepatide removed from shortage list. This directly impacts compounding availability.