I would like to understand the process rather than be told to try harder.
The empirical answer seems settled. The explanation does not.
If the honest answer is that nobody knows, I would rather hear that than a plausible story.
Why does this happen, and what would falsify the usual explanation?
The short version: legitimate under a prescription within defined limits, unapproved by definition, and quality depends entirely on the facility.
Beyond-use dates on compounded sterile preparations are set by standards that depend on the preparation environment and are much shorter than a manufactured product's shelf life.
Facility quality varies enormously and is the practical determinant of what you receive. The relevant questions are about sterility assurance, potency testing and beyond-use dating.
Regulatory warnings have specifically addressed salt forms differing from the approved active moiety in this therapeutic area.
The framework is jurisdiction-specific. Check yours rather than a general answer.
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsAnswering this needs the jurisdiction, since the framework differs substantially between countries and even between states.
A compounded preparation has no marketing authorisation, no batch release by a qualified person and no pharmacovigilance obligation attached to it. That is the structural difference from a licensed product.
Ask for the certificate of analysis on the compounded lot. A serious facility will have one; the request itself is informative.
Beyond-use dating for compounded sterile preparations is governed by published standards keyed to the compounding environment.
Compounded means unapproved by definition. That is structural, not pejorative.
The honest answer is that a well-run compounding pharmacy is a serious operation and that the variance across facilities is wide.
Salt forms matter: a compounded preparation using a different salt from the approved product is not the same active moiety, and that has been the specific object of regulatory warnings.
The underlying point is that compounding is the preparation of a medicine for an individual patient in response to a prescription, where an approved product is unsuitable. It sits outside the approval framework by design rather than by omission.
Ask which salt form. A different salt is a different active moiety.
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.