Photodynamic therapy for acne vulgaris: a critical review from basics to clinical practice: part II. Understanding parameters for acne treatment with photodynamic therapy

Photodynamic therapy requires a photosensitizer, oxygen, and activating light. For acne, pilosebaceous units are "target" structures. Porphyrins are synthesized in vivo from 5-aminolevulinic acid (ALA), particularly in pilosebaceous units. Different photosensitizers and drug delivery methods have been reported for acne treatment. There are a variety of porphyrin precursors with different pharmacokinetic properties. Among them, ALA and methyl-ester of ALA (MAL) are available for possible off-label treatment of acne vulgaris. In addition, various light sources, light dosimetry, drug incubation time, and pre- and posttreatment care also change efficacy and side effects. None of these variables has been optimized for acne treatment, but a number of clinical trials provide helpful guidance. In this paper, we critically analyze clinical trials, case reports, and series of cases published through 2009. After completing this learning activity, participants should be able to analyze photodynamic therapy using 5-aminolevulinic acid and its derivates for acne treatment, predict the effectiveness and outcomes of photodynamic therapy using different parameters and/or different porphyrin-related photosensitizers, and assess and manage the side effects of porphyrin-based photodynamic therapy for acne.