PharmHunterJen said:If two explanations both fit, the useful question is which one predicts something the other does not.
Adding the part of the answer the thread has not reached. 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.
One concrete data point for the thread. For anyone reading later: the numbers in this thread are worth checking against a primary source before you act on them, including mine. Half the figures circulating in this community trace back to a secondary summary that dropped a qualifier.
Following on from PharmHunterJen — 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?
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Browse GL BiochemDr.NateNeph said:For anyone reading later: the numbers in this thread are worth checking against a primary source before you act on them, including mine.
I am going to disagree with the direction of travel here. The thread has converged on the tidiest answer rather than the best-supported one, and those are not the same thing.
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.