Photodynamic Therapy With PD P 506 A Compared With Placebo-PDT for the Treatment of AK

Inclusion Criteria: * Written informed consent * Caucasian patients * Diagnosis of actinic keratosis (AK) with at least three locally separated lesions located on head and/or face (hairless areas) * Selected AK study lesions have clearly defined margins and are mild to moderate * The distance between the study lesion borders is \> 1.0 cm * Maximum diameter of each study lesion is 1.8 cm * Skin sun sensitivity type I to IV according to Fitzpatrick Exclusion Criteria: * PDT Non-responder * Pre-treatment of the AK lesions eligible for study procedures with pharmaceuticals approved for the treatment of AK during the 4 weeks preceding PDT * Pre-treatment of the AK lesions eligible for study procedures during the 2 weeks preceding PDT with keratolytic agents e.g. TCA, urea or salicylic acid containing formulations * Pre-treatment with hypericin during the 2 weeks preceding PDT * Treatment with systemic retinoids during the 3 months preceding PDT * Treatment with cytostatics or radiation during the 3 months preceding PDT * Female patients of childbearing potential * Patients with clinically relevant suppression of the immune system * Diagnosis of Porphyria * Skin diseases that might interfere with response evaluation of study PDT * Skin sun sensitivity type V or VI according to Fitzpatrick * Known intolerance to one or more of the ingredients of the study medication * Dementia or psychic condition that might interfere with the ability to understand the study and thus give a written informed consent * Simultaneous participation in another clinical study or participation in another clinical study in the 30 days directly preceding inclusion * Suspected lack of compliance