title: Pain associated with photodynamic therapy using 5-aminolevulinic acid or 5-aminolevulinic acid methylester on tape-stripped normal skin.
abstract: BACKGROUND
  Pain during and after topical photodynamic therapy (PDT) is one of the few severe adverse effects of the new treatment of skin diseases.
  
  
  OBJECTIVE
  To compare the pain experienced in normal skin treated with 5-aminolevulinic acid (ALA) PDT and 5-aminolevulinic methylester (ALA-ME) PDT.
  
  
  METHODS
  Double-blind randomized trial.
  
  
  METHODS
  Twenty healthy volunteers were treated randomly with ALA-PDT on one forearm and ALA-ME-PDT on the other forearm after tape stripping of the sun-exposed skin areas.
  
  
  METHODS
  Pain was scored using a numerical scale ranging from 0 to 10 during illumination, immediately after illumination, and each day in the following week. In addition, we measured erythema, pigmentation, and protoporphyrin IX (PpIX) fluorescence.
  
  
  RESULTS
  ALA-PDT generated significantly more pain than ALA-ME-PDT during and after illumination (P =.001 and P =.05, respectively). ALA-PDT induced a larger decrease in PpIX fluorescence than ALA-ME-PDT (P =.009). There was no correlation between pain and peak PpIX fluorescence or absolute decrease in peak PpIX fluorescence. Both treatments lead to erythema immediately after illumination and increased pigmentation 1 week after PDT. There was no correlation between pain and degree of erythema or pigmentation.
  
  
  CONCLUSIONS
  ALA-ME-PDT was less painful than ALA-PDT when performed on tape-stripped normal skin. The pain scores did not correlate with the intensity of peak PpIX fluorescence in the skin or with the degree of erythema after illumination, suggesting that pain was not caused by activation of PpIX alone. The theory that ALA and not ALA-ME is transported by gamma-aminobutyric acid receptors into the peripheral nerve endings may explain the higher pain scores in ALA-PDT-treated areas.
authors.affiliation: Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Denmark. SRW01@bbh.hosp.dk
authors.forename: Stine Regin
authors.initials: SR
authors.lastname: Wiegell
authors.forename: Ida-Marie
authors.initials: IM
authors.lastname: Stender
authors.forename: Renhua
authors.initials: R
authors.lastname: Na
authors.forename: Hans Christian
authors.initials: HC
authors.lastname: Wulf
mesh_terms: D000328:Adult; D000622:Aminolevulinic Acid / Q000009:adverse effects* / Q000494:pharmacology; D004311:Double-Blind Method; D004951:Esterification; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000009:adverse effects* / Q000494:pharmacology; D010146:Pain / Q000209:etiology*; D010147:Pain Measurement; D010778:Photochemotherapy / Q000009:adverse effects*; D017319:Photosensitizing Agents / Q000009:adverse effects* / Q000494:pharmacology; D012016:Reference Values; D013997:Time Factors
chemical_list: D008738:Methyl Ethers; D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid