title: Topical application of 5-aminolaevulinic acid, methyl 5-aminolaevulinate and hexyl 5-aminolaevulinate on normal human skin.
abstract: BACKGROUND
  5-Aminolaevulinic acid (ALA) and its ester derivatives are used in photodynamic therapy. Despite extensive investigations, the differences in biodistribution and pharmacokinetics of protoporphyrin IX (PpIX) induced by ALA and its derivatives are still not well understood, notably for humans.
  
  
  OBJECTIVE
  To study porphyrin accumulation after topical application of ALA and two of its ester derivatives in normal human skin.
  
  
  METHODS
  Creams containing 0.2%, 2% and 20% (w/w) of ALA, methyl 5-aminolaevulinate (MAL) and hexyl 5-aminolaevulinate (HAL) were applied on normal human skin of six volunteers. The amount and distribution of porphyrins formed in the skin was investigated noninvasively by means of fluorescence spectroscopy.
  
  
  RESULTS
  Fluorescence emission and excitation spectra exhibited similar spectral shapes for the all drugs, indicating that mainly PpIX was formed. Low concentrations (0.2% and 2%) of MAL induced considerably less PpIX in normal human skin than similar concentrations of ALA and HAL. A high concentration (20%) of ALA gave higher PpIX fluorescence in normal human skin than was found for MAL and HAL.
  
  
  CONCLUSIONS
  The concentrations inducing half of the maximal PpIX fluorescence are around 2% for ALA, 8% for MAL and 1% for HAL.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, 0310 Montebello, Oslo, Norway. asta.juzeniene@klinmed.uio.no
authors.forename: A
authors.initials: A
authors.lastname: Juzeniene
authors.forename: P
authors.initials: P
authors.lastname: Juzenas
authors.forename: L-W
authors.initials: LW
authors.lastname: Ma
authors.forename: V
authors.initials: V
authors.lastname: Iani
authors.forename: J
authors.initials: J
authors.lastname: Moan
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D000622:Aminolevulinic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000493:pharmacokinetics*; D006801:Humans; D008875:Middle Aged; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D011524:Protoporphyrins / Q000493:pharmacokinetics; D012867:Skin / Q000378:metabolism*; D012869:Skin Absorption; D013050:Spectrometry, Fluorescence
chemical_list: D017319:Photosensitizing Agents; D011524:Protoporphyrins; C475457:methyl 5-aminolevulinate; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX; C419924:5-aminolevulinic acid hexyl ester