Manufacturing without process validation and stability testing - the quickest way to receiving a warning letter
Recommendation

10/11 February 2026
Risk analysis, preventive measures and incident management
When FDA inspectors examine a production facility, they expect compliance with basic and obvious GMP requirements, such as the testing of a finished product for compliance with its specifications prior to its release. During the inspection of the Chinese company Luen Wah in Hong Kong, they had to discover that the production of OTC products in this facility runs without this final testing; a number of other basic GMP rules had also been plainly ignored. After an insufficient response by the manufacturer, a warning letter was issued half a year later. The following GMP violations were described:
Final testing for compliance with specifications
As mentioned above, this final testing for identity and strength of the active ingredient had not been performed; the testing for total aerobic microbial count of the products was missing, especially.
Testing for identity of the components and reliability of the supplier's certificates of analysis
Neither APIs nor excipients of the drug product had been tested for identity, strength and purity upon receipt. The values from the supplier's certificate of analysis had been adopted unverified.
Stability testing and expiration date
There were no stability studies and therefore no data on which the expiration date of the product indicated on the label could be based on.
Process validation
Process validation had never been performed. Neither were there any qualification studies nor a program for monitoring the manufacturing process.
As is the case in many other warning letters, the FDA recommends the company to employ a consultant in order to eliminate the deficiencies. The warning letter states a consultant had been present during the inspection; however, the agency strongly recommends calling in a consultant qualified according to 21 CFR 211.34.
Luen Wah has been placed on Import Alert on 18 January.
Please also see the FDA warning letter to Luen Wah (HK) Medicine for further information.
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