Development and Validation of a Methodology for Testing Topical Antipruritic Drugs Using Experimentally Induced Pruritus.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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A new double-blind methodology for testing the efficacy of topical antipruritic drugs was evaluated in a series of four experiments. Hair of rose hips was impregnated with histamine and applied to two or three sites on each forearm of volunteers. Pruritus intensity at each site was measured 2 minutes after application of the hair of rose hips baseline and 2, 5, 10, 15 and 20 minutes after application of topical study drugs. In experiment 1, the mean pruritus scores were significantly lower for hydrocortisone 0.5 plus chlorcyclizine 2 vs. placebo at the 5 and 10 minute time points p0.017, but there were no significant differences at any time point in experiment 2. There was a statistically significant decrease in the intensity of pruritus in repeat volunteers following treatment with dibucaine experiment 3 and calamine experiment 4 as compared to their respective placebo. This effect was not present in volunteers naive to the study. The methodology was thus validated with experienced volunteers but not with volunteers who had not previously participated in the study.