title: Comparison of the effects of levocetirizine and loratadine on histamine-induced wheal, flare, and itch in human skin.
abstract: BACKGROUND
  This randomized, double-blind, crossover study compared the effects of the R-enantiomer of cetirizine, levocetirizine, with those of loratadine on the wheal, flare, and itch response to histamine in human skin.
  
  
  METHODS
  Levocetirizine (5 mg), loratadine (10 mg), or placebo was taken orally 4 h before the intradermal injection of histamine (20 microl, 100 microM) or the control vehicle into the forearm skin of healthy volunteers. Flare areas were assessed by scanning laser Doppler imaging before and at 30-s intervals for a period of 9 min. Wheal areas were measured by planimetry at 10 min. Itch was scored every 30 s with a visual analogue scale.
  
  
  RESULTS
  After placebo administration, the mean peak flare area was 23.01+/-1.94 cm(2), the wheal area 248+/-27 mm(2), and the cumulative itch score 28.8+/-4.6% (mean+/-SEM). Levocetirizine reduced the flare, wheal, and itch by 60%, 68%, and 91%, respectively (all P<0.001, Student's t-test for paired data). The effects of loratadine were variable and not statistically significant.
  
  
  CONCLUSIONS
  Levocetirizine (5 mg) is a potent inhibitor of the effects of histamine in human skin with an efficacy that exceeded that of loratadine (10 mg) when single doses of the drugs were administered 4 h before the test.
authors.affiliation: Dermatopharmacology Unit, Allergy and Inflammation Sciences, School of Medicine, University of Southampton, Southampton, UK.
authors.forename: G F
authors.initials: GF
authors.lastname: Clough
authors.forename: P
authors.initials: P
authors.lastname: Boutsiouki
authors.forename: M K
authors.initials: MK
authors.lastname: Church
mesh_terms: D018926:Anti-Allergic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D017332:Cetirizine / Q000008:administration & dosage / Q000627:therapeutic use*; D004311:Double-Blind Method; D006632:Histamine; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000139:chemically induced / Q000188:drug therapy*; D017336:Loratadine / Q000008:administration & dosage / Q000627:therapeutic use*; D012882:Skin Tests; D014581:Urticaria / Q000188:drug therapy
chemical_list: D018926:Anti-Allergic Agents; D017336:Loratadine; D006632:Histamine; D017332:Cetirizine