In Vivo Monitoring Of Drug Penetration In Human Skin Using Reflectance Technique

Abstract

Apparent drug penetration by skin was non-invasively using light monitored reflectance at 632.8 nm. The method uses a commercially available low-power He-Ne laser device and a multimode optical fibre. Specially designed Perspex light pipe was used to monitor light reflected from the skin. Five creams and ointments having different composition and clinical application purpose were investigated. It was found that apparent drug penetration by skin depends considerably on the type and application of the drug and the type and the location of the skin’s testing area. The time-dependent penetration of the drug into skin was characterized by two slopes. A positive slope attributed to drug penetration into skin and a negative slope attributed to absorption of the drug by the microcirculation. By using visible He-Ne laser light, the absorption of the drug into deeper skin layers can be followed. The time of maximum drug absorption (maximum reflectance) was found to be between 3 and 12 minutes. This method may be easily applied for drug penetration follow-up studies and drug modeling.