Panelists: lowering preservative content likely requires new stability studies; include preservative-effectiveness data if formulations mix antioxidants
Summary
When applicants propose reducing preservative concentration for ocular tolerability, panelists said new stability studies showing preservative content at the revised formulation are needed; if antioxidants compete with preservatives, include a study addressing that interaction in the application.
An online participant asked whether a slight reduction in preservative concentration to improve ocular tolerability would allow acceptance of USP <51> results on the finished product at end of shelf life, or whether a new stability study would be required.
Dr. Chen said the agency requests preservative content data at or below the minimum specification to ensure no additional microbial growth, and that applicants should provide new stability studies showing preservative content at the new formulation. On a follow-up about combinations of preservative and antioxidants that could interfere with a preservative effectiveness test, Dr. Chen said including a study of that interaction in the application "would be helpful" but that the primary preservative testing should be sufficient.
Panelists recommended that applicants include preservative- and antioxidant-interaction data in their submissions when relevant and that they provide stability data that reflect the proposed preservative concentration over shelf life.
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