Percutaneous penetration

Abstract

Many intrinsic and extrinsic factors affect percutaneous absorption rates. Percutaneous absorption is measured in vivo through different methods, including radioactivity measurements in the blood and excreta, surface recovery, surface disappearance, biological and pharmacological responses, the stripping method, and human-skin-flap method. In vitro methods include measuring absorption rates through excised skin into a receptacle designed to mimic actual dermatological conditions. Measuring the radioactivity in a subject’s blood and excreta is commonly practiced, and involves administering a compound often radiolabeled, in order to measure the amount of the original dose that has penetrated the skin. Surface recovery and disappearance methods involve administering a compound on the skin and measuring the rate of recovery from the surface of the skin or the rate of its disappearance. The stripping method deals with measuring the concentration of a chemical in the stratum corneum through successive tape applications and removals. Efforts are being made to standardize the most commonly used in vitro assay. The vehicle by which a compound is transferred to the skin has an effect on its absorption rate.