Test No. 427: Skin Absorption: In Vivo Method

         The in vivo percutaneous absorption study set out in this Test Guideline provides the linkage necessary to extrapolate from oral studies when making safety assessments following dermal exposure. The in vivo method, described in this guideline, allows the determination of the penetration of the test substance through the skin into the systemic compartment.         The test substance, preferably radiolabelled, is applied, for a fixed period of time, to the clipped skin of animals at one or more appropriate dose levels in the form of a representative in-use preparation. The rat is the most commonly used species. At least four animals of one sex should be used for each test preparation and each scheduled termination time. A known amount of the test preparation is evenly applied to the site. This amount should normally mimic potential human exposure, typically 1-5 mg/cm² for a solid or up to 10 µl/cm² for liquids. A relevant exposure period (typically 6 or 24 hours) should be used, based on the expected human exposure duration. The animals should be observed for signs of toxicity/abnormal reactions at intervals for the entire duration of the study. This study includes: daily measurements (excreta), regular detailed observations, as well as sacrifice at the scheduled time and blood collected for analysis.      