Levulan: the first approved topical photosensitizer for the treatment of actinic keratosis.

Actinic keratosis (AK) is a very common skin problem found in patients over 50 years of age, representing an in situ keratinocytic neoplasm that can progress to invasive squamous cell carcinoma of the skin. One Food and Drug Administration-approved treatment for AK of the face and scalp is photodynamic therapy (PDT) with 20% aminolevulinic acid (ALA). This advanced technology has been demonstrated in clinical trials to be effective and well tolerated by patients.