title: An intraindividual comparative study of psoralen-UVA erythema induced by bath 8-methoxypsoralen and 4, 5', 8-trimethylpsoralen.
abstract: BACKGROUND
  Limited work has been conducted on the characteristics of topical trimethylpsoralen (TMP) psoralen-UVA (PUVA) erythema.
  
  
  OBJECTIVE
  We sought to determine the time-course and dose-response characteristics of erythema induced by topical TMP, and to compare these parameters with those for topical 8-methoxypsoralen (MOP) within patients.
  
  
  METHODS
  After photosensitization of one forearm with topical TMP, test sites were exposed to a UVA dose series. The procedure was repeated on the other forearm using 8-MOP solution. Erythema was assessed visually and with a reflectance instrument every 24 hours for 7 days.
  
  
  RESULTS
  TMP PUVA erythema followed a similar time course to 8-MOP PUVA erythema. The majority of patients were at maximal erythema at or beyond 96 hours. TMP PUVA had a significantly steeper dose-response curve at 48, 72, and 96 hours compared with 8-MOP PUVA.
  
  
  CONCLUSIONS
  On the basis of these data, the optimal time to read the TMP minimal phototoxic dose is 96 hours. In view of the steeper dose-response curve for TMP PUVA, a lower UVA incremental regimen should be considered compared with that for 8-MOP PUVA.
authors.affiliation: Photobiology Unit, Department of Dermatology, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland.
authors.forename: Irene
authors.initials: I
authors.lastname: Man
authors.forename: Jayne
authors.initials: J
authors.lastname: McKinlay
authors.forename: Robert S
authors.initials: RS
authors.lastname: Dawe
authors.forename: James
authors.initials: J
authors.lastname: Ferguson
authors.forename: Sally H
authors.initials: SH
authors.lastname: Ibbotson
mesh_terms: D000328:Adult; D004305:Dose-Response Relationship, Drug; D004890:Erythema / Q000139:chemically induced*; D005260:Female; D006801:Humans; D008297:Male; D008730:Methoxsalen / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D011701:PUVA Therapy / Q000379:methods; D013997:Time Factors; D014307:Trioxsalen / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D008730:Methoxsalen; D014307:Trioxsalen