Background: The aim of this paper is to evaluate a simple in vitro skin penetration experiment
in which the drug is extracted from the whole skin piece as a test valid for formulation screening
and optimization during development process, equivalence assessment during quality control or postapproval
after changes to the product.
Methods: Twelve clobetasol propionate (CP) formulations (six creams and six ointments, being five
generics and one reference from each formulation type) from the local market were used as a model to
challenge the evaluated methodology in comparison to in vitro skin penetration following tape-stripping
for drug extraction. To support the results, physicochemical tests for pH, viscosity, density and assay, as
well as in vitro release were performed.
Results: Both protocols, extracting the drug from the skin using the tape-stripping technique or extracting
from the full skin were capable of differentiating CP formulations. Only one formulation did not
present statistical difference from the reference drug product in penetration tests and only other two
oitments presented equivalent release to the reference. The protocol is straightforward and reproducible.
Conclusion: Results suggest the bioinequavalence of tested CP formulations reinforcing the necessity
of such evaluations.