FDA Warning Letter: Deficiencies in Stability Testing, Supplier Qualification, Validation and CGMP Oversight

The U.S. Food and Drug Administration (FDA) has published a new Warning Letter dated 1 September 2026 concerning a manufacturer of over-the-counter (OTC) drug products based in Maryland.

Following an inspection conducted from 30 March to 2 April 2026, the agency identified significant violations of the CGMP requirements for finished pharmaceuticals under 21 CFR Parts 210 and 211.

Identification Testing on Raw Materials

One of the deficiencies concerned the testing and qualification of incoming materials. The firm had not performed at least one specific identity test for each component before use. In the case of an API, testing was limited to organoleptic examination, while the supplier had also not been adequately qualified or requalified.

The FDA therefore requested a comprehensive and independent review of the material system, including supplier qualification, material quality, retest and expiry dates, and the use and verification of supplier Certificates of Analysis.

Stability Testing

The FDA also found that the stability program was inadequate. Accelerated stability studies lacked complete information on controlled humidity conditions, included unavailable timepoints, and contained an out-of-specification (OOS) viscosity result that had not been investigated. A failing viscosity result in an ongoing long-term study had likewise not been adequately addressed.

The FDA requested a comprehensive remediation plan covering stability-indicating methods, marketed container-closure systems, the annual inclusion of representative batches, predefined testing at each timepoint, and the relevant procedures.

Quality Unit Oversight and Validation Deficiencies

Further deficiencies related to the quality unit (QU) and the overall quality system. The quality unit had not ensured adequate oversight of manufacturing and testing activities.

Among other issues, the FDA cited the absence of process validation for the over-the-counter drug products, the lack of cleaning validation for non-dedicated equipment, recurring gasket seal failures that had not been appropriately addressed through CAPA, and inadequate release specifications for APIs in finished products.

Although the firm had committed to establishing and executing process and cleaning validation protocols, the FDA found during the 2026 inspection that these activities had not been completed.

FDA Requests Clarification on Future Drug Production

The firm had indicated that it would cease production of certain drugs at the facility. The FDA requested clarification on whether additional batches had been manufactured after the inspection or whether drug manufacturing might resume.

Any resumption would require the deficiencies and underlying systemic weaknesses to be fully addressed. The FDA also recommended engaging a qualified consultant to conduct a comprehensive six-system CGMP audit and to evaluate the completion and effectiveness of the CAPA measures before the firm seeks resolution of its compliance status.

In addition, the FDA requested an action plan addressing potential product quality or patient safety risks for batches already distributed in the United States, including potential customer notifications, recalls, or market withdrawals.

For further information, please see the complete Warning Letter to Happy Farm Botanicals, Inc. on the FDA's website.