FDA Warning Letter to U.S.-based OTC Manufacturer: Deficiencies in Release Testing, Raw Material Controls and Stability Program

The U.S. Food and Drug Administration (FDA) issued a Warning Letter to a drug manufacturer located in Michigan, USA, following an inspection conducted in March/April 2025. The document dated 22 September was published online on 04 November 2025.

The agency identified multiple critical violations of Current Good Manufacturing Practice (CGMP) requirements under 21 CFR Parts 210 and 211.

Missing Finished Product Testing Prior to Release

The company released OTC hand hygiene products (including foaming antibacterial soap and antimicrobial handwash) without ensuring that each batch conformed to final specifications.
According to the inspection findings:

• No documented identity and strength testing of active ingredients for all batches
• No routine microbiological testing of process water
• No microbiological testing of finished product batches

Insufficient Identity Testing for High-Risk Raw Materials

The FDA also found that the firm did not adequately test incoming raw materials, including glycerin, for potential contamination with diethylene glycol (DEG) and ethylene glycol (EG). The identity testing procedure did not include the required USP limit test components.

Given the well-documented global incidents involving DEG/EG contamination, the agency highlighted the need for routine and specific identity testing in accordance with compendial methods.

Lack of an Adequate Stability Program

The stability program in place did not demonstrate that product quality is maintained throughout the labeled shelf life.

The Warning Letter states: "You failed to establish an adequate stability testing program to demonstrate that the chemical and microbiological properties of your drug products meets established specifications and remain acceptable through the 12-month expiration period for your drug products. During the inspection, you informed our investigator that reserve samples stored are also considered stability samples. You indicated that you only inspect them visually for color appearance and do not record the results."

Deficient Quality Unit Oversight and Documentation Practices

The FDA noted significant weaknesses in the Quality Unit (QU).

Key issues included:

• Absence of adequate SOPs for investigations, CAPA, change control, batch release, and recalls
• Incomplete batch records (e.g., missing mixing times, lot numbers, test results)
• Lack of documented final batch review prior to release

The agency concluded that the QU did not have the authority or systems required to ensure CGMP compliance.

FDA Expectations

The Warning Letter requires the firm to submit comprehensive corrective and preventive actions, including:

• Robust chemical and microbiological release testing
• Full identity testing of incoming high-risk raw materials
• A scientifically sound stability program using validated methods
• A fully empowered and resourced Quality Unit with effective oversight mechanisms

For further information, please see the complete Warning Letter to Kath Khemicals LLC on the FDA's website.