LabKate 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…

Compounding pharmacy response time test for compounded supply: I email customer service at odd hours to test responsiveness. A pharmacy that can't answer questions promptly is a red flag.

My current pharmacy: average response time 1 hour. They answered my questions about batch-specific COAs thoroughly and professionally.

Communication quality is a proxy for operational quality. A pharmacy that communicates well is likely manufacturing well too.

Following on from Dr.BariatricHTX — and this may be the naive question:

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

jason_paloalto said:

Compounding pharmacy response time test for compounded supply: I email customer service at odd hours to test responsiveness.

Beyond-use dating (BUD) for compounded supply compounded products:

Lyophilized (unreconstituted): typically 9 months from compounding date
Reconstituted with BAC water: typically 28-30 days refrigerated
Reconstituted with sterile water: typically 7 days (no preservative!)

Always use BAC water for multi-dose vials. Sterile water has no preservative and supports bacterial growth after first puncture. This is a common and potentially dangerous mistake.

Reporting back.

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.

SleepDoc_PDX said:

Beyond-use dating (BUD) for compounded supply compounded products: Lyophilized (unreconstituted): typically 9 months from compounding date…

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.