Photodynamic therapy using direct-current pulsed iontophoresis for 5-aminolevulinic acid application

In photodynamic therapy (PDT) for skin cancer, 5-aminolevulinic acid (ALA) is applied topically to the affected area to be absorbed percutaneously through passive diffusion, and typically requires 4-6 h before performing PDT. In this study, we attempted to reduce the absorption period in PDT by ionizing ALA using direct-current pulsed iontophoresis to treat actinic keratosis (AK). Twenty percent ALA solution was applied to AK lesions of five patients using direct-current pulsed iontophoresis. ALA-PDT was repeated three times with a total irradiation of 150 J/cm(2) (50 J/cm(2) per irradiation, weekly). One week after the last PDT, therapeutic results were assessed by skin biopsy. In all subjects, protoporphyrin IX (PpIX) production was confirmed after iontophoresis, and its production levels were comparable to the conventional occlusive dressing technique (ODT). Skin biopsies from the treated lesion showed the disappearance of tumour cells. These results indicated that direct-current pulsed iontophoresis for applying ALA before PDT is useful to treat AK.