Finite Dose In Vitro Permeation Testing: Significance of Occluding the Donor compartment, a Case study

The evaporation of the solvent induces significant changes in formulation, directly impacting its performance. The performance of topical products is determined by the interplay between their inherent quality attributes and the transformations that occur due to solvent evaporation when applied to the skin in clinically relevant doses. To accurately assess, in vivo performance, it is advisable to apply smaller doses to the skin and keep the donor compartment open to enable evaporation of solvents while carrying out in vitro permeation tests. This manuscript highlights the critical role of solvent evaporation in differentiating the performance of two compositionally distinct products. One gel formulation contained alcohol, while the other did not. Although both exhibited similar quality attributes, their drying profiles varied significantly. Permeation studies conducted with closed donor compartments (Evaporation-disabled (ED)) failed to reveal these differences. However, when the donor compartments were exposed to the atmosphere to allow evaporation (Evaporation-enabled (EN)), the performance differences between the two products became evident.