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FDA warns sponsors about mixing, solvent and percent‑solids weaknesses in transdermal systems
Summary
CDER’s presentation cited missing temperature controls during mixing, inadequate redispersion data for multiphase systems, and wide percent‑solids ranges that can alter API solubility; presenters urged development studies and defined bulk viscosity tests.
Amit Kokate, of the Office of Pharmaceutical Manufacturing Assessment at CDER, described recurring mixing‑stage weaknesses in transdermal delivery system (TDS) submissions. He said reviewers frequently see temperature increases reported in submissions without an accompanying control strategy and recommended that sponsors implement temperature controls and upper limits for mixing parameters.
Kokate also highlighted gaps in data demonstrating re‑dispersion of multiphase systems and the absence of justified bulk viscosity testing for drug‑adhesive matrices. "So our suggestion here is to implement a bulk viscosity test with meaningful limits, in your, in module 3," he said. He recommended development studies to demonstrate that remixing restores the dispersion and setting maximum hold times and mixing controls where appropriate.
