Charles River performs in vitro skin absorption testing on topical formulations in support of the pharmaceutical, agrochemical, chemical, cosmetic, and consumer products industries.
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Topical Formulation Development & Bioequivalence

Topical Formulation Testing

Are your topical formulations effective? An in vitro skin absorption test for your topical products can give you the critical answer to this question. We’ve been running this test in support of the pharmaceutical, agrochemical, chemical, cosmetic, and consumer products industries for over 30 years, and are ready to perform the necessary testing in support of your topical, dermal, and transdermal products.

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Selecting a lead candidate is a critical part of drug discovery, but for topical products the potential for drug delivery is often overlooked, leading to expensive efficacy programs without confirmed skin delivery. Lead candidate molecules are applied to the skin in model or simple formulations and analyzed for drug and transdermal delivery. Once a lead candidate has been chosen, the optimization of the topical formulation is the next critical step in the development of the drug. Different topical formulation types are required based on the physicochemical properties of the drug substance and where in the body it is intended to be active.

For topical testing, both the test item alone and the formulation, or a realistic final formulation, are used in GLP safety tests. We prepare simple “families” of topical formulations and then test them for absorption and dermal delivery in vitro in human skin before selecting the formulation family to optimize the formulation through human in vitro skin absorption testing. Once a formulation has been selected, we can take it and the test item through the formal testing program.

Topical Bioequivalence

The FDA and EMA have generated draft guidance for topical bioequivalence. Our expertise in clinical bioanalysis and skin absorption puts us in a unique position to run generic topical bioequivalence testing. Our paper (Mitra et al., 2016) describes the basic procedures that are followed, although the specific guidelines are utilized for each regulatory agency. Aside from following the guidelines, the FDA is open to innovations and, as such, we are innovating with bioequivalence testing in the skin layers which is often more important for a dermal drug than what is absorbed. We’re happy to discuss these and other innovations with you.


We use a wide variety of analytical techniques in support of testing, and this is no different for topical bioequivalence or topical formulation development, especially using LC-MS/MS, GC-MS, and ICP-MS. Our Bioanalytical Services page offers additional details on bioanalysis.

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