CTK OTC Labs Hit With FDA Warning Letter For Not Conducting Batch Failure Investigations
June 7th, 2025 // 5:09 pm @ jmpickett
FDA sent a warning letter to CTK OTC Labs, located in Corona, California, in June 2025 for not conducting thorough investigations into batch failures related to its manufacturing of topical creams and sunscreens.
FDA investigators stated that CTK OTC Labs didn’t conduct sufficient investigations of out-of-specification (OOS) results for batches which had low potency values for one of the APIs. The root cause of subpar potency wasn’t determined. Furthermore, batch failures related to high viscosity of the creams were not investigated.
The company was also criticized by FDA for failing to validate its manufacturing processes for several topical sunscreens and creams. Also, the firm couldn’t offer studies for blend uniformity to show that the mixing processes could have regular uniformity and homogeneity. These problems caused the OOS results FDA noted.
Failure To Investigate Failures of a Batch to Meet Specifications – 21 CFR 211.192
The warning letter stated that the firm’s corrective action was to remix the batch in November 2024 to increase uniformity. The batch remained subpotent after the re-mix. The firm adjusted the potency by putting in more APIs and remixing. But the root cause was never pinpointed. Also, the bulk base batch had another OOS result for viscosity that was too high. The firm didn’t look into the viscosity OOS issue and the bulk base batch was released. It was used to make finished drug batches. Some finished drug batches were reviewed during stability and also had high viscosity. This result wasn’t investigated.
FDA noted that when there was an investigation, it was subpar because root causes were not determined. Nor were corrective and preventive actions (CAPAs) implemented, and there wasn’t sufficient investigation to review the effects on other products and batches.
The response was deemed inadequate because the firm only committed to improve the investigation process without doing any impact assessment of drug products that were previously distributed.
FDA warned that not addressing these failures could lead to the company’s expert certificates being withheld.
