Noninvasive in Vivo Percutaneous Absorption Measurements Using X-Ray Fluorescence

Abstract
X-ray fluorescence (XRF) has been used to determine in vivo the percutaneous absorption of 5-iodouracil (5IU) in dimethyl sulfoxide (DMSO) on female Sprague-Dawley rats. An average absorption rate constant of 122 ± 34 µg/cm2-hr was obtained from the XRF measurements on four rats. A comparative study was performed with radiolabeled (125I) 5IU in which the absorption rate constant was determined to be 126 ± 20 µg/cm2-hr. The XRF system described provides a simple, noninvasive means of measuring the percutaneous absorption rate of select compounds by the surface disappearance method.