Glossary
Essentially a copy: FDA’s test for duplicating a marketed drug
"Essentially a copy of a commercially available drug product" is FDA’s test for a compounded preparation that duplicates something already on the market, and it is a restriction on what may be compounded at all rather than on who may receive it. FDA applies it on two elements — the same active ingredient at the same, similar or an easily substitutable strength, and a marketed product usable by the same route of administration — with an exception that runs through a prescriber who determines and documents that the compounded product contains a change producing a significant difference for an identified individual patient. Shortage-list status switches the test off while it lasts, and back on when it ends.
The test, in FDA’s words
FDA states the test as two elements plus an exception. Both elements have to be present before the restriction bites:
the compounded drug product has the same active pharmaceutical ingredient(s) (API) as the commercially available drug product in the same, similar or an easily substitutable strength, and the commercially available drug product can be used by the same route of administration (regardless of how it is labeled) prescribed for the compounded drug product. This is unless a prescriber determines and documents the compounded drug product contains a change that produces a significant difference from the commercially available drug product for an identified individual patient.
Three things are worth reading carefully. The route element is a defeater: where no marketed product can be used by the route prescribed, the second element is not satisfied and the test does not bite. The exception is written to run through the prescriber, who determines and documents the significant difference for a named patient — it is not a certification the compounder makes about its own catalogue. And the operative words are "significant difference," which is not the same as a difference the prescriber prefers.
What shortage status changes
A marketed product that is on FDA’s shortage list is treated as not commercially available while it is there:
A drug is not considered to be commercially available if it is on FDA's drug shortages list and limitations on compounding essentially copies are not applicable in these circumstances.
This is the most perishable fact in the subject. Shortage status is per presentation and it moves, so it is a dated answer rather than a standing one — and when a shortage ends the restriction switches back on. On the outsourcing-facility side, FDA has said it may act where a facility keeps filling new orders after the marketed product comes off the shortage list.
What it does and does not decide
This restriction is about what may be compounded. It says nothing about who may receive the result, which is the separate question answered by the patient-specific prescription condition and by office use. A preparation can clear this test and still be unavailable to a practice as cabinet stock, and the reverse.
The argument in full — how the exception is actually used, what adding an ingredient does and does not achieve, and which substances the test presses hardest on — is in essentially a copy of a commercially available drug. The dated, per-substance picture is kept on the compounding status tracker, and the two pathways it applies across are compared in 503A vs 503B. What the restriction is measuring the preparation against — and why an approved product on the shortage list stops counting as one — is at compounded and commercially available compared.