Evaluation of skin absorption of drugs from topical and transdermal formulations

ABSTRACT The skin barrier function has been attributed to the stratum corneum and represents a major challenge in clinical practice pertaining to cutaneous administration of drugs. Despite this, a large number of bioactive compounds have been successfully administered via cutaneous administration because of advances in the design of topical and transdermal formulations. In vitro and in vivo evaluations of these novel drug delivery systems are necessary to characterize their quality and efficacy. This review covers the most well-known methods for assessing the cutaneous absorption of drugs as an auxiliary tool for pharmaceutical formulation scientists in the design of drug delivery systems. In vitro methods as skin permeation assays using Franz-type diffusion cells, cutaneous retention and tape-stripping methods to study the cutaneous penetration of drugs, and in vivo evaluations as pre-clinical pharmacokinetic studies in animal models are discussed. Alternative approaches to cutaneous microdialysis are also covered. Recent advances in research on skin absorption of drugs and the effect of skin absorption enhancers, as investigated using confocal laser scanning microscopy, Raman confocal microscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy, are reviewed

Interpretation of English tense morphophonology by advanced L2 speakers

This study tests the assumption in much of the literature on the second language acquisition of English tense and aspect morphophonology (e.g. bare verbs, V-ing, V-ed) that once speakers are beyond intermediate levels of proficiency, both distribution and interpretation of these forms are represented in a target-like way in their mental grammars. Three groups of advanced non-native speakers (whose L1s were Chinese, Japanese and the verb-raising languages Arabic, French, German and Spanish) were compared with native speakers on an acceptability judgement task requiring informants to judge the appropriateness of sentences involving different verb forms to contexts which privileged specific interpretations. The results suggest an effect of the persistent influence of parametric differences between languages such that where parametrised grammatical properties are not activated in the L1, they are not available for the construction of representations in the L2.</jats:p