FDA WARNING_LETTER - Tower Laboratories Ltd. - July 11, 2025

The FDA issued a Warning Letter to Tower Laboratories Ltd. following an inspection from July 8-11, 2025, at its Montague, MI drug manufacturing facility. The letter outlines significant violations of Current Good Manufacturing Practice (CGMP) regulations for finished pharmaceuticals (21 CFR parts 210 and 211), leading to the adulteration of the company’s drug products under the Federal Food, Drug, and Cosmetic Act.

Key violations include the failure to thoroughly investigate out-of-specification (OOS) laboratory results for over-the-counter (OTC) drug products, particularly concerning stability failures. The company repeatedly attributed OOS results to "microscopic packaging defects" without adequate scientific evidence or implementing effective corrective and preventive actions (CAPA), a repeated observation from a previous inspection. Furthermore, customers were not notified of these failing stability results for distributed lots.

The FDA also cited Tower Laboratories Ltd. for failing to establish adequate laboratory controls. Specifically, their sample preparation methods for high-performance liquid chromatography analysis were unsuitable, using a solvent that degrades the active ingredient, potentially generating inaccurate OOS results.

To address these issues, the FDA requires Tower Laboratories Ltd. to conduct a retrospective, independent review of all invalidated OOS results for U.S. products, identifying conclusive root causes and remediating affected methods. The company must also provide a comprehensive remediation plan for its OOS investigation systems, enhancing quality unit oversight, root cause evaluation, and CAPA effectiveness. Finally, an evaluation and retrospective review of all analytical sample preparation methods, including a risk assessment of past test results, is mandated.