FDA Warning Letter: Missing Testing for Toxic Impurities and Lack of Stability Data in OTC Drug Products

In a recent Warning Letter dated 09 April 2025, the U.S. Food and Drug Administration (FDA) outlines multiple, serious violations of current Good Manufacturing Practice (CGMP) observed during an inspection of a U.S.-based over-the-counter (OTC) drug manufacturer. The letter, published on 29 April 2025, refers to an inspection performed from 28 October to 01 November 2024.

Inadequate Testing of High-Risk Raw Materials

The firm failed to perform identity testing for critical components such as glycerin, propylene glycol, and ethanol – substances with a known risk of contamination by diethylene glycol (DEG), ethylene glycol (EG), or methanol. These contaminants have caused fatal poisoning incidents globally. The company relied solely on supplier certificates of analysis (COAs) without verifying their reliability.

No Stability Data to Support Expiry Dates

OTC drug products were distributed with assigned shelf lives, yet no stability studies had been performed. The FDA found that the firm lacked both a written stability program and appropriate testing (e.g., microbial limits, impurities) to demonstrate that products remain within specification throughout their shelf life.

Missing Process and Equipment Validation

The company manufactured numerous batches of liquid OTC hand sanitizer and antibacterial soap without validated processes or qualified equipment. Critical parameters such as mixing speed and time had never been studied, and cleaning validation was not performed.

Deficient Quality Oversight

The FDA noted a lack of written procedures for core quality functions. The Quality Unit (QU) had not conducted annual product reviews, failed to ensure data integrity controls, and lacked authority and oversight across operations.

FDA Response and Recommendations

The agency requested a number of corrective actions and recommends engaging a qualified GMP consultant to assist the firm in meeting CGMP requirements. Failure to comply may result in further regulatory action.

For further information, please see the Warning Letter to Dyno Manufacturing, Inc. on the FDA's website.