Stability Study for EMLA Cream Using In Vitro Percutaneous Absorption “IVPT”

EMLA Cream (lidocaine 2.5% and prilocaine 2.5%) is an emulsion in which the oil phase is a eutectic mixture of lidocaine and prilocaine. It is a numbing cream that can be placed on skin to provide pain relief. It is often used to numb an area before placing an IV, drawing blood, or giving injections.
Typical stability study is conducted by the assay of active pharmaceutical ingredient (API) in the drug product. However, the assay results may not indicate drug product’s penetration rate similarity between different products over a certain period of time frame because of the differences in its topical product qualities (such as rheology, particle size, excipients, penetration enhancers, etc.). Therefore, it is important to evaluate the penetration of compounds into human skin during drug product stability study.
In vitro human cadaver skin model using Franz diffusion cells (invented in 1975) is widely regarded as the most valid in vitro model for evaluating the penetration of compounds into human skin. It can be used to determine the product equivalence.