Comparative in vivo study of precursors of PpIX (ALA and MAL) used topically in Photodynamic Therapy

The efficacy of Photodynamic Therapy (PDT) combined with aminolevulinic acid (ALA) or methyl aminolevulinate (MAL) in treatment of cancer has been studied for over ten years. However, there is no established dose for the topical use of these drugs in PDT. The purpose of this study was the comparison of induced PDT response of ALAsense (5-aminolevulinic acid - ALA) and Metvix (methyl aminolevulinate - MAL). Depth of necrosis induced by PDT was analyzed in normal liver of male Wistar rats, using different light doses and topical application of both PpIX precursors - ALA and MAL. PDT was performed with a diode laser at 630 nm with different doses of light (20, 50, 100 and 200 J/cm 2 ), and intensity of 250 mW/cm 2 . Depth of necrosis analysis was used to calculate the threshold dose for each drug. The results showed that MAL-PDT presented a better response than ALA-PDT, mainly due to formulation differences. Moreover, the ability of the ALA PpIX production was more efficient.