The phototoxicity of photodynamic therapy may be suppressed or enhanced by modulation of the cutaneous vasculature

Salvador González, Chitralada Vibhagool, Margaret Sherwood, Thomas J. Flotte, Nik Kollias

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


In photodynamic therapy, the threshold for light induced toxicity depends on the drug concentration and the light dose. This study was aimed to show for vascular photosensitizers that the toxicity threshold on normal tissue may be predictably modified by modulation of the cutaneous vasculature. Albino rabbits were injected with 1.0 mg/kg of a vascular photosensitizer, benzoporphyrin derivative monoacid ring-A. The threshold light dose for toxicity to normal skin was determined at an absorption maximum of the drug (694 nm), 1 h after drug injection. The cutaneous vasculature was dilated by prior skin exposure to ultraviolet radiation or was constricted by iontophoretic application of epinephrine. Threshold toxicity was determined clinically and by assessing the effective concentration of hemoglobin in the skin by diffuse reflectance spectroscopy (DRS). Tissue samples that received threshold doses were investigated with light and electron microscopy. The toxicity threshold increased by 3.2±0.9 (mean±S.D.) following vasoconstriction and decreased by 3.6±0.8 following vasodilation, compared to control sites. Light and electron microscopy showed similar findings at threshold for both vasodilated and vasoconstricted sites. Therefore vascular modulation may be used to predictably enhance or suppress the level of phototoxicity of normal skin. (C) 2000 Elsevier Science S.A. All rights reserved.

Original languageEnglish (US)
Pages (from-to)142-148
Number of pages7
JournalJournal of Photochemistry and Photobiology B: Biology
Issue number2-3
StatePublished - 2000


  • Benzoporphyrin derivative
  • Epinephrine-iontophoresis
  • Erythema
  • Skin phototoxicity
  • UVB radiation
  • Vascular modulation

ASJC Scopus subject areas

  • Radiation
  • Radiological and Ultrasound Technology
  • Biophysics
  • Radiology Nuclear Medicine and imaging


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