CTK OTC Laboratories LLC – FDA Warning Letter, Dec 31, 2024

On May 19, 2025, the FDA issued a Warning Letter to CTK OTC Laboratories LLC (formerly FMK LABS, Inc.) following an inspection from December 16-31, 2024, at their Corona, California drug manufacturing facility. The letter cites significant violations of Current Good Manufacturing Practice (CGMP) regulations for finished pharmaceuticals (21 CFR parts 210 and 211), rendering their drug products adulterated.

Key violations include: 1. **Inadequate Investigations (21 CFR 211.192):** The firm failed to thoroughly investigate Out-of-Specification (OOS) results, such as low potency and high viscosity in a bulk base batch, which subsequently affected finished drug products. Their response was deemed inadequate for not proposing a retrospective impact assessment. 2. **Inadequate Production and Process Controls (21 CFR 211.100(a)):** * **Inadequate Process Validation:** The firm failed to validate manufacturing processes for OTC drug products, lacking blend uniformity studies. Their commitment to validate was insufficient due to lack of supporting documentation, timelines, or retrospective assessment. * **Inadequate Water System Validation:** The water system used for manufacturing and cleaning was not validated, routinely maintained, or sanitized. Microbiological samples showed bacterial and fungal growth, which were not identified. Their response lacked a detailed remediation plan