title: The effect of lidocaine on PpIX photobleaching and outcome of ALA-PDT in vitro.
abstract: BACKGROUND
  Photodynamic therapy (PDT) is based on the light exposure of neoplastic tissue after selective accumulation of photosensitizers in neoplastic cells. One of the major side effects of ALA-PDT is pain during light exposure. Lidocaine is one of several anaesthetics used to relieve this pain. Although its anaesthetic role is well known, it has been proposed that it may act as a hydroxyl radical and singlet oxygen scavenger. The effectiveness of PDT is directly linked to the yield of singlet oxygen. The aim of this study was to investigate possible scavenging properties of lidocaine in photosensitization.
  
  
  METHODS
  Photodegradation of PpIX in dimethyl sulfoxide (DMSO) solution and in WiDr cells alone or in the presence of lidocaine was investigated by fluorescence spectroscopy. The influence of lidocaine on PDT outcome was evaluated by measuring the colony forming ability of the cells.
  
  
  RESULTS
  Lidocaine in DMSO had no significant effect (p<0.05) on PpIX photodegradation, although it seems to induce a slight increase in the photobleaching rate. The rate of PpIX photodegradation and the photosensitivity in cells were similar in the absence and in the presence of lidocaine.
  
  
  CONCLUSIONS
  Lidocaine had no significant influence on PpIX photobleaching and ALA-PDT outcome in vitro.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Center, Montebello, 0310 Oslo, Norway.
authors.forename: Patrycja
authors.initials: P
authors.lastname: Mikolajewska
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Center, Montebello, 0310 Oslo, Norway.
authors.forename: Asta
authors.initials: A
authors.lastname: Juzeniene
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Center, Montebello, 0310 Oslo, Norway; Institute of Physics, University of Oslo, Blindern, 0316 Oslo, Norway.
authors.forename: Johan
authors.initials: J
authors.lastname: Moan