Effect of H1- and H2-receptor blockade on the inhibition of immediate cutaneous reactions.

The effects of cyproheptadine, cimetidine, and their combination on the wheal-and-flare skin-test response was evaluated using an intradermal skin-test technique in a double-blind, placebo-controlled study. Sixteen volunteers with known positive skin-test reactions to at least two antigens were divided into four treatment groups in a four-way crossover design. The patients received baseline intradermal skin tests on the back consisting of dilutions of mixed grasses and weeds, histamine diphosphate and codeine phosphate, and buffered-saline control. Following the baseline testing, the patients received cyproheptadine (4 mg q.i.d.), cimetidine (300 mg q.i.d.), the combination, and placebo in a double-blind trial. Of the 16 patients, 12 completed all treatment courses. Following pretreatment with cyproheptadine, cimetidine, and the combination, areas of wheal-and-flare response for each test substance were significantly suppressed. Although it appeared that the combination augmented wheal-and-flare suppression, the observed difference, compared with the cyproheptadine pretreatment sequence, was not statistically significant. The administration of H1 and H2 antagonists should be discontinued before the diagnostic use of immediate skin tests.

RCT Entities:   Population Interventions Outcomes