Facilitated delivery of ALA to inaccessible regions via bioadhesive patch systems.

5-Aminolevulinic acid (ALA) is now being increasingly used in photodynamic therapy (PDT) and photodiagnosis (PDD) of lesions of the oral cavity, esophagus, and female genital tract. Clearly, topically applied creams and solutions are not the most suitable drug delivery systems for such moist and irregularly shaped areas, where shear forces may be high. As a result, such areas of the body are currently relatively inaccessible to efficient topical delivery of ALA.

Spectroscopic measurements of photoinduced processes in human skin after topical application of the hexyl ester of 5-aminolevulinic acid.

Although 5-aminolevulinic acid, ALA, and its derivatives, have been widely studied and applied in clinical photodynamic therapy (PDT), there is still a lack of reliable and non-invasive methods and technologies to evaluate physiological parameters of relevance for the therapy, such as erythema, melanogenesis, and oxygen level. We have investigated the kinetics of these parameters in human skin in vivo during and after PDT with the hexyl ester of ALA, ALA-Hex. Furthermore, the depth of photosensitizer (protoporphyrin IX, PpIX) production after different application times was investigated.