Compounded sema batch testing results — need advice

julia.endo said:

They are two different exemptions from the same federal requirements and they buy different things.

Pushing back on julia.endo 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.

steve_okc 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…

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.

SarahChen_PharmD said:

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

Compounding pharmacy licensing verification for compounded supply: before ordering, verify your pharmacy's credentials:

1. State Board of Pharmacy license — check on your state BOP website
2. FDA registration (for 503B) — check on fda.gov
3. DEA registration if handling controlled substances
4. PCAB accreditation — voluntary but demonstrates commitment to quality
5. USP <797>/<800> compliance for sterile compounding

This takes 10 minutes of research and could save you from receiving substandard or unsafe medication.

One thing that is still open after Dr.EndoIndy’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.