Influence of different layers of skin on the percutaneous absorption of drugs with different lipophilicity

Objectives: To evaluate the barrier function of different skin layers in the process of percutaneous drug absorption. Methods: In vitro permeability via intact or stripped skin of 6 drugs (5-fluorouracil, theo-phylline, hydroquinone, barbital, isosorbide dinitrate and ketoprofen) with a wide span of lipophilicity were investigated in the patch dosage forms. Results: Characteristic parabolic relations was observed between the permeability (Kp, cm/h) of the drugs with different lipophilicity and their LogPc via either intact or stripped skin. However, due to the absence of the stratum corneum, increased Kp ratio for the tested drugs was proportional to their solubility in water other than their LogKp. When isopropyl myristate was used as absorption promoter of the drugs, the parabolic relationship no longer existed. For the intact skin, increase of Kp ratio of the drugs was enhanced resulting from IPM as drug's LogPc decreased. On the other hand, in the case of stripped skin, this enhancement was positively related to the solubility of the drugs in IPM. Conclusion : These data and methods present a novel approach to describe percutaneous drug absorption via damaged or diseased skin.

Influence of in vitro Methods, Receptor Fluids on Percutaneous Absorption and Validation of a Novel in vitro Method

In vitro experiment using excised skin has been valuable for studying the mechanism of percutaneous absorption. Based on previously established static diffusion cell system in this laboratory, a novel model-peifused glass diffusion cell system is desboed. The results of initial comporative study on percutaneous absorption between glass perfused diffusion cell and static diffusion cell, ih vitro and in vivo permeation as well as factors affecting permeation with seven radiolabelled chemicals are presented. The results demonstrate that the peifused diffusion cell system, which used a perfusion nuid betow the suiface of skin to take up the materials which penetrated the skin, is more similar to physiologic condition,convenient and automatic than that of the static cell. It well predicts the in vivo percutaneous absorption if appropriate areptor fluid is chosen. The results also show that the selection of receptor fluid is critical for in vitro permeation of chemicals with different soubility

Transdermal Permeation of Dihydro Etorphine Hydro- chloride-Influence of pH,Concentration and Surfactantson in vitro Permeation

Effects of pH , donor phase concentration and surfactants on skin permeation in vitro were investigated using excised rat skin. Percutaneous absorption rate of dihydro etorphine hydrochloride(DHE)was increased in the of pH5,pH3,pH7 and pH9.When the DHE concentration was from 20 to 80μg/ml,the permeation rate at different concentrations was ratherstable at pH 7 and9,but was intricated at pH 3 and 5.Skin penneation treated with1,propanediol,Azone,and 3% menthol in 50% ethanol solution increased the permeability of DHE by1. 16,1.95,4.86 times ,respectively.

In Vitro Skin Permeation of Osthol from Hydro-Alcoholic Gel Formulations

Aim To evaluate the in vitro percutaneous absorption behavior of osthol from a series of hydro-alcoholic gel formulations containing three penetration enhancers through excised human skin (stratum cormeum and epidermis,SCE). Methods Excised human skin was mounted in Franz-type diffusion cells. The samples withdrawn from the receptor cell were analyzed for osthol content by high-performance liquid chromatography (HPLC). Results The enhancers azone,menthol and chenopodium increased the osthol percutaneous steady-state fluxes 3.12, 2.00 and 1.25 times those of the enhancer-free formulations (controls), separately. Conclusions The main enhancement mechanism of the skin penetration enhancers azone, menthol and chenopodium is to destroy the barrier function of stratum corneum, reducing the resistance of drug transport through the skin and increasing the diffusion coefficients of osthol.

Expert consensus on the technical specifications of the in vitro skin penetration test of cosmetic product by Franz diffusion cell

Background:Diffusion cell test is one of the most commonly used in vitro model to detect the percutaneous absorption of cosmetic ingredients.Although PRC State Administration of Quality Supervision and Quarantine has issued the guideline for the in vitro test method for the percutaneous absorption of drug molecules,there is still a lack of guideline for the percutaneous absorption test of cosmetic components.Objective:In order to improve the standardized level and make the in vitro percutaneous absorption test of cosmetic ingredients more comparable,based on the international and domestic experience,Transdermal Drug Delivery Committee of the World Federation of Chinese Medicine Societies organized the experts to discuss and formed this consensus as reference for the percutaneous absorption test of cosmetic components.Materials and Methods:To standardize the in vitro diffusion cell test technique for transdermal penetration of functional cosmetic ingredients,the Transdermal Drug Delivery Professional Committee of the World Federation of Societies of Traditional Chinese Medicine has organized many discussions among experts.