What percentage of applied methyl aminolevulinate was absorbed through human skin after 24 hours in an in vitro study?

Metvix product information reports mean cumulative absorption of radiolabelled methyl aminolevulinate through human skin of 0.26% of the administered dose after 24 hours in vitro; corresponding studies were not performed in skin with actinic-keratosis-like damage and an additionally roughened surface, or without stratum corneum.