RetaRick_CA said:

The shortage clause is the answer to the second question and it is a subtraction rather than an addition.

Pushing back on RetaRick_CA 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.

CarlaRPh_TPA said:

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

GMP compliance checklist relevant to compounded supply compounding quality:

• Clean room environment with HEPA filtration
• Environmental monitoring (viable and non-viable)
• Personnel training and competency assessment
• Validated analytical methods for testing
• Stability testing program
• Complete batch records and traceability
• Quality management system with deviation handling

A 503B pharmacy following cGMP should be able to answer questions about ALL of these if you ask. Don't be afraid to ask — it's your health.

LabKate said:

A research-chemical supplier selling lyophilised powder labelled research use only is not compounding and is not claiming to.

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.

One thing that is still open after JessicaH_TX’s answer:

What actually distinguishes 503A from 503B, in terms of what each may make and from what starting material?

OP back with an update, since a thread like this is useless without one.

The bulks-list asymmetry was the piece I had missed entirely. It explains why one of my two pharmacies is still arguing it can supply and the other simply stopped.