Evaluation of in vitro tests to assess the efficacy of formulations as topical skin protectants against organophosphorus compounds

Prevention of exposure to the neurotoxic organophosphorus compounds (OP) is a major concern both for pesticide users and soldiers. Skin barrier creams are being developed to complement or replace uncomfortable chemical protective suits. Quick evaluation of formulations efficacy mainly relies on in vitro tests which lead to consistent, complementary and relevant results. The objectives of this work were to determine the consistency of results from in vitro tests and importance of the formulation composition in the skin protective efficacy. The efficacy of three formulations, i.e. oil-in-water and water-in-oil emulsions and perfluorinated compounds-based cream, was evaluated against the OP paraoxon in vitro. Our results indicated that the least effective formulations could be quickly identified by performing in vitro permeation tests with silicone membrane and by evaluating interfacial interactions between formulations and OP. Among the tested formulations, the perfluorinated compounds-based cream could have a broader spectrum of efficacy than emulsions against OP and other toxic chemicals.