Posting this because the summary going around does not say what the paper says, and the difference matters for how people here are using 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.
Where I think it is weakest: the comparator does most of the work in how this gets reported, and it is not the comparator most people think they are citing.
What would genuinely help is knowing what actually distinguishes 503A from 503B, in terms of what each may make and from what starting material. Happy to be told the question itself is 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.
paul_denver said:They are two different exemptions from the same federal requirements and they buy different things.
That is correct as far as it goes, and here is where it stops going. 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.
paul_denver said:They are two different exemptions from the same federal requirements and they buy different things.
Pushing back on paul_denver here. 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.
Sigma-Aldrich — Research-Grade Standards
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsShort answer first, then the reasoning. 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.
I would rather be corrected than agreed with, if it comes to it.
Dr.NateNeph said:Resolution therefore closed the doors unevenly, and the asymmetry follows from the bulks lists.
This is my experience too, for whatever a second data point is worth. I had assumed I was the exception until I read this.