Read the primary source rather than the write-up and the two do not agree, so here is what is actually in it.
Resolution therefore closed the doors unevenly, and the asymmetry follows from the bulks lists. For 503B the shortage clause was the only route to these molecules, so that route shut completely. A 503A pharmacy can still argue a doorway via "component of an approved drug" — but only for the substance in the form present in the approved product, which is exactly where the base-versus-salt argument lives, and it does nothing about the copy restriction, which came back into force on resolution.
Where I think it is weakest: the subgroup findings are the part I trust least — with enough subgroups something is always significant, and these were not all pre-registered.
What I actually want to know is 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.
Figures above are from the primary publication rather than the press summary. If a number here disagrees with one you have, post yours and we will work out which of us is reading a secondary source.
DoseLogDan said:Resolution therefore closed the doors unevenly, and the asymmetry follows from the bulks lists.
DoseLogDan has the substance of this right. The condition it depends on is worth stating. 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.
DoseLogDan said:Resolution therefore closed the doors unevenly, and the asymmetry follows from the bulks lists.
This is where I part company with the consensus forming above. A research-chemical supplier selling lyophilised powder labelled research use only is not compounding and is not claiming to. It is a different legal universe with no pharmacy oversight, no patient relationship and no content guarantee, and conflating the two in these threads helps nobody.
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Shop Reference StandardsTaking the question as asked, rather than the general version of it. 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.
LabKate said:The shortage clause is the answer to the second question and it is a subtraction rather than an addition.
Same experience, arrived at from the opposite direction. The detail I would add is minor and it is already implied above.