Stratum Corneum Reservoir Capacity Affecting Dynamics of Transdermal Drug Delivery

Abstract

A number of researches ^1-5 have reported the observations of reservoir capacity in human stratum corneum since Vickers clearly demonstrated this phenomenon in 1963 ⁶. Both lipophilic and hydrophilic drugs may be trapped in the matrix-structure of stratum corneum and diffuse out very slowly due to strong binding and/or markedly low diffusivlty (10 ⁻¹⁰-10 ^{−11cm 2} /S) ^{7, 8}. since it affects significantly the dynamics of transdermal drug delivery, the reservoir capacity of the stratum corneum should be thoroughly investigated before a transdermal drug delivery system is developed. In spite of the evidence of the stratum corneum reservoir effect, its mechanism has not yet been fully elucidated. There is no quantitative interpretation reported in the literature which could assist us to gain a fundamental understanding the dynamic characteristics of stratum corneum reservoir capacity.