ABSTRACT
Most photosensitizers used in PDT are derivatives of hematoporphyrin, an endogenous porphyrin that was fi rst synthesized from heme in the mid-19th century. In 1913, Meyer-Betz (4) was the fi rst to demonstrate the “photodynamic effect” in vivo after he injected himself with hematoporphyrin and noticed that the areas exposed to light became swollen and painful. Unfortunately, the phototoxic reaction lasted for 2 months. In 1942, Auler and Banzer (5) demonstrated the ability of hematoporphyrin to concentrate more in certain dermatologic tumors than in their surrounding tissues. Histological analysis also showed that tumors were necrotic, confi rming the photodynamic response of hematoporphyrin. However, large doses
of hematoporphyrins were required for photosensitization, resulting in subsequent severe phototoxic reactions.
