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1 October 2000 Comparison of the Pharmacokinetics and Phototoxicity of Protoporphyrin IX Metabolized from 5-Aminolevulinic Acid and Two Derivatives in Human Skin In Vivo
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Abstract

Our novel approach was to compare the pharmacokinetics of 5-aminolevulinic acid (ALA), ALA-n-butyl and ALA-n-hexylester induced protoporphyrin IX (PpIX), together with the phototoxicity after photodynamic therapy (PDT) in human skin in vivo, using iontophoresis as a dose-control system. A series of four increasing doses of each compound was iontophoresed into healthy skin of 10 volunteers. The kinetics of PpIX metabolism (n = 4) and the response to PDT (n = 6) performed 5 h after iontophoresis, were assessed by surface PpIX fluorescence and post-irradiation erythema. Whilst ALA-induced PpIX peaked at 7.5 h, highest PpIX fluorescence induced by ALA-n-hexylester was observed at 3–6 h and no clear peak was seen with ALA-n-butylester. With ALA-n-hexylester, more PpIX was formed after 3 (P < 0.05) and 4.5 h, than with ALA or ALA-n-butylester. All compounds showed a linear correlation between logarithm of dose and PpIX fluorescence/phototoxicity at 5 h, with R-values ranging from 0.87 to 1. In addition, the ALA-n-hexylester showed the tendency to cause greater erythema than ALA and ALA-n-butylester. Fluorescence microscopy (n = 2) showed similar PpIX distributions and penetration depths for the three drugs, although both ALA esters led to a more homogeneous PpIX localization. Hence, ALA-n-hexylester appears to have slightly more favorable characteristics for PDT than ALA or ALA-n-butylester.

Sandra Gerscher, James P. Connelly, John Griffiths, Stanley B. Brown, Alexander J. MacRobert, Gavin Wong, and Lesley E. Rhodes "Comparison of the Pharmacokinetics and Phototoxicity of Protoporphyrin IX Metabolized from 5-Aminolevulinic Acid and Two Derivatives in Human Skin In Vivo," Photochemistry and Photobiology 72(4), 569-574, (1 October 2000). https://doi.org/10.1562/0031-8655(2000)072<0569:COTPAP>2.0.CO;2
Received: 11 April 2000; Accepted: 1 July 2000; Published: 1 October 2000
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