Statement of APC Chief Executive Officer Scott Brunner, CAE, on statements by Eli Lilly claiming an unknown impurity in sampled tirzepatide + B12 drugs

March 12, 2026 • 2:00PM EDT

Lilly’s announcement today that it has observed “impurities” in compounded tirzepatide + B12 is concerning, but we don’t know much based on what the drugmaker has said so far. We’ve got heat without much light.

Consider: B12 is a well-studied and remarkably benign drug. We are about four years into the compounding of prescriber-authorized tirzepatide + B12, and there’s no alarming trend of patient adverse events associated with the compounded drug. Yet Lilly says they’ve “uncovered” some significant interaction that they assert puts patients at risk.

That raises some questions. Anyone reading Lilly’s statement should have these questions, because both Lilly and Novo have done this before: announced the results of sampling of “compounded GLP-1s” without identifying whether the source of those drugs sampled were actually state-licensed compounding pharmacies, as opposed to unlicensed or illicit actors. A med spa is not a pharmacy, and in 46 states, med spas are not bound by the sourcing requirements legitimate pharmacies must adhere to. A bogus website or offshore source of a supposed GLP-1 combo drug, available without a prescription, is an illegal entity, not a pharmacy, and what they are selling are illicit substances, not compounded drugs. Are Lilly’s samples from those? We don’t know. All they say is "Lilly tested compounded products being marketed to Americans."

Nor does Lilly, in its statement, answer some necessary questions about the disposition of the drugs sampled, the answers to which matter a great deal in terms of how seriously to take the claims they’re making about those samples:

• How did a corporation acquire a sample of a drug that requires a patient-specific prescription – were they legally obtained?
• If they were legally obtained, how old was the drug sampled?
• Had it been properly refrigerated and handled?
• Was the seal intact when the drug was sampled?

The answers to those questions matter when we’re talking about the presence of impurities or other contamination. Lilly’s statement says nothing about these very salient factors.

Beyond those essential questions, one should ask: what is the "impurity” Lilly discovered? And what is a “significant amount,” and how are they determining that? All drugs, even FDA-approved drugs, are allowed a certain level of impurities that do not negatively affect the patient. Is this new-found impurity within the allowed profile?

It may be that Lilly has identified a real issue involving tirzepatide + B12 prepared by legitimate, state-licensed compounding pharmacies. If so, APC would take that extremely seriously. Patient safety is paramount, and we would expect the FDA and state boards of pharmacy to move quickly to investigate and address any verified risk. But at this point, Lilly has not provided enough information about the source of the samples, the handling of the drugs, or the nature and magnitude of the alleged impurity for anyone outside the company to evaluate the claim.

No doubt, today’s statement from Lilly will garner some headlines. But patient safety deserves evidence, not insinuation. If Lilly has data demonstrating a genuine safety concern, it should share that information transparently with regulators and the public so it can be evaluated on the merits. Until then, today’s announcement raises more questions than it answers.

Scott Brunner, CAE is Chief Executive Officer for the Alliance for Pharmacy Compounding.