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5‐ALA for photodynamic photorejuvenation—optimization of treatment regime based on normal‐skin fluorescence measurements
Author(s) -
Christiansen Kaare,
Bjerring Peter,
Troilius Agneta
Publication year - 2007
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.20488
Subject(s) - fluorescence , photodynamic therapy , chemistry , liposome , dermatology , medicine , optics , biochemistry , physics , organic chemistry
Background and Objectives Photodynamic therapy using 20% 5 aminolevulinic acid (5‐ALA) has recently been introduced as a new tool in optical skin rejuvenation. The primary objective of this study was to optimize incubation time, the topical delivery mechanism (vehicle) and the concentration of 5‐ALA by detecting the dynamic changes of normal skin after 5‐ALA application. The secondary objective was to develop a treatment regime which minimizes post‐treatment photosensitivity. Study Design/Materials and Methods Skin fluorescence distribution patterns after topical application of low concentrations of 5‐ALA (0.5% and 1% preparations encapsulated in liposomes), were investigated. Twenty percent 5‐ALA in moisturizing cream was used as a control. Ten healthy volunteers participated, and skin fluorescence was documented by fluorescent photography. The fluorescent intensity was measured in % of maximum obtained fluorescence after 3 hours 5‐ALA application. Results Skin fluorescence intensity after topical application of 0.5% and 1% non‐occluded liposome‐encapsulated 5‐ALA application was heterogeneous distributed and reached saturation level after approximate 2 hours. The maximal fluorescence for 0.5% and 1% 5‐ALA treated areas was 4.2% (SD: 3.5%) and 2.4% (SD: 2%), respectively, and this difference was statistically significant ( P = 0.036). The fluorescence decayed linearly shortly (within 15 minutes) after end of application and was back to baseline within 8 hours. In contrast, the fluorescence of areas treated more than 1 hour with 20% 5‐ALA was very uniform and a linear relationship ( r 2 = 0.998) to the incubation time (0–3 hours) was registered. Furthermore, fluorescence intensity (15.2–57.9%) continued to increase after the end of 5‐ALA application. The maximum fluorescence reach a level of 1.6–9 times the fluorescence measured by end of the 5‐ALA application and occurred 8:13 hours (SD: 0:49 hours) after the end of 20% 5‐ALA application. The average skin surface fluorescence induced by the liposome‐encapsulated 0.5% 5‐ALA applied for longer than 2 hours, was found to be statistically equal ( P = 0.47) to the average measured skin surface fluorescence (4.2%) obtained after 30 minutes exposure to 20% 5‐ALA cream (4.3%). Conclusion Changing the 5‐ALA vehicle from a moisturizing cream to liposome encapsulation, the 5‐ALA concentration can be lowered by a factor of 40, and still induce the same skin fluorescence and at the same time eliminates the need for occlusion. The low post‐treatment fluorescence also suggests a significantly reduced risk of post‐treatment phototoxicity. Lasers Surg. Med. 39: 302–310, 2007. © 2007 Wiley‐Liss, Inc.