Mounjaro pen vs compounded vial - pros and cons?

Taking the question as asked, rather than the general version of it. 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.

Dr.ObesityMed 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.

MounjBrad said:

My pharmacy stopped supplying with three weeks notice and a letter that explained nothing, so I went and read the statute.

Can confirm the pattern MounjBrad describes. 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.

From the other side of the consultation, briefly.

503A vs 503B compounding pharmacies for compounded supply — this distinction matters enormously:

I strongly recommend 503B facilities. The FDA oversight and cGMP requirements mean more consistent product quality.