Time to break and evaporation (TBE): A quality attribute of pharmaceutical topical foams

The quality attributes of topical foams are critical in determining the rate and extent of drug absorption across the skin and mucous membranes. A generic product is required to match the reference-listed drug (RLD), with respect to its composition and characteristics. Time to break (TB) is one of the critical quality attributes to consider during the evaluation of some of the generic products, as per the product-specific guidance from the Food and Drug Administration (FDA). This paper proposes a slightly modified protocol for conducting TB studies to improve the robustness of the test and reduce the ambiguity in its assessment. The proposed modified method "Time to Break and Evaporation (TBE)" is a gravimetric method that considers the collapse and loss of solvents and other volatile components from the foam. A marketed salicylic acid foam product was used as a model to demonstrate the practicality of this modified approach.