title: Screening topical antipruritics: a histamine-induced itch human model.
abstract: Itch is a subjective symptom; its magnitude (intensity) may be only estimated by the reports of patients or volunteers. We utilized a comparative screening method to identify and quantify the efficacy of topical antipruritics with a histamine-induced itch human model. Ten individuals responsive to histamine-induced itch sensation were enrolled. Both forearms served as test sites. Each test site was treated randomly either by histamine injection only or pretreated with a coded candidate formula for 30 min and then a histamine injection. Itch was experimentally induced in each test site by the intracutaneous injection of 100 microg histamine dihydrochloride dissolved in 1 ml normal saline. Itch magnitude was measured each minute after histamine injection for 20 min with a magnitude visual analogue scale. Itch duration was also recorded. Formulation D significantly (p < 0.05) decreased itch magnitude (within a 20-min test period), from 2.6 +/- 2.1 cm (mean +/- SD) to 2.2 +/- 2.1 cm (mean +/- SD) when compared to its vehicle control; it also significantly (p < 0.05) shortened itch duration (15.0 +/- 7.4 min; mean +/- SD) in comparison with its vehicle control (20.3 +/- 7.0 min; mean +/- SD). Of all the formulations tested, formulation D was the most effective antipruritic in decreasing histamine-induced itch. This method may act as a simple and robust screening procedure when evaluating potential antipruritics and allow a comparison among products. Until validated with disease-induced itch, e.g., atopic dermatitis, the model should be considered screening in nature.
authors.affiliation: Department of Dermatology, School of Medicine, University of California, San Francisco, Calif 94143-0989, USA.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Zhai
authors.forename: F Anthony
authors.initials: FA
authors.lastname: Simion
authors.forename: Eric
authors.initials: E
authors.lastname: Abrutyn
authors.forename: Almuth M
authors.initials: AM
authors.lastname: Koehler
authors.forename: Howard I
authors.initials: HI
authors.lastname: Maibach
mesh_terms: D000279:Administration, Cutaneous; D000982:Antipruritics / Q000627:therapeutic use*; D005260:Female; D005542:Forearm; D006632:Histamine; D006801:Humans; D006854:Hydrocortisone / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009025:Morpholines / Q000627:therapeutic use*; D011537:Pruritus / Q000139:chemically induced / Q000188:drug therapy*
chemical_list: D000982:Antipruritics; D009025:Morpholines; C005548:pramoxine; D006632:Histamine; D006854:Hydrocortisone