Fresenius Kabi Letter Shows How an FDA Inspection Becomes a Warning Letter

The Food and Drug Administration has issued a warning letter dated Sept. 22 to Fresenius Kabi USA, citing what it called significant violations of current good manufacturing practice (CGMP) rules at the company's sterile injectable drug plant in Melrose Park, Illinois. The letter, from FDA's Center for Drug Evaluation and Research, says that because the plant's methods, facilities or controls do not conform to CGMP, its drug products are adulterated under the Federal Food, Drug, and Cosmetic Act. BioPharm International reported on the letter on Oct. 1.

The letter also shows, step by step, how FDA's inspection findings become a public enforcement document. FDA's description of the Form 483 that starts the process covers food, drug, device and cosmetic makers alike.

Step one: the inspection and the Form 483

According to the letter, FDA inspected the Melrose Park facility from Jan. 27 to Feb. 18, 2026. At the end of an inspection, investigators can hand the company an FDA Form 483. FDA's Form 483 frequently asked questions say the form is issued to management when an investigator has observed conditions that "in their judgment may constitute violations" of the FD&C Act and related laws, and that each observation is read and discussed with senior management.

The form is not a verdict. FDA says it "does not constitute a final Agency determination" of whether any condition violates the law, and that it is not an all-inclusive list, since investigators note only what they saw. The agency considers the 483 together with a written Establishment Inspection Report, the evidence collected on site and any responses from the company, and then decides what further action, if any, is appropriate. Companies are encouraged to respond in writing with a corrective action plan.

Step two: the response and the letter

Fresenius Kabi responded on March 11, according to the warning letter, which says FDA "reviewed your March 11, 2026, response to our Form FDA 483 in detail." The letter then takes the violations one by one, summarizing the company's commitments and stating after several of them, "Your response is inadequate."

Among the findings, FDA wrote that the company received reports in 2025 and 2026 of adverse drug events, including apparent pyrogenic reactions, after administration of famotidine for injection; that later testing of retained samples revealed an endotoxin failure; and that the firm recalled three famotidine batches. The letter also cites media fill failures on aseptic lines in 2024 and 2025 and at least nine incidents of extrinsic contamination, such as hair, documented since May 2022.

FDA's page "About Warning and Close-Out Letters" says the agency often uses a warning letter when it identifies what it believes are significant violations, and that the letter gives the recipient a chance to address the concerns, or to disagree and supply its reasoning, within a set time. This letter asks for a written response within 15 business days. It says failure to address the violations may result in regulatory or legal action without further notice, including seizure and injunction, and that FDA may withhold approval of new applications or supplements listing the firm as a manufacturer until it confirms compliance.

Step three: verification and close-out

A warning letter stays open until FDA checks the work. Under the close-out program for letters issued since Sept. 1, 2009, FDA says it may issue a close-out letter once it has evaluated the firm's corrective actions, but "a close-out letter will not be issued based on representations that some action will or has been taken." The corrections must be made and verified, the agency says, usually through a follow-up inspection. If a letter cites violations that by their nature cannot be corrected, no close-out letter is issued.

BioPharm International noted that the letter is heavily redacted and that the company's full corrective action plan has not been made public.