Effect of betamethasone on the dual reaction to anti-human IgE in man: influence of time interval between administration of drug and anti-IgE.

The influence of the time interval between administration of a glucocorticoid, betamethasone, and anti-IgE on the effect of the drug on the early and late phase response (LPR) to anti-IgE was examined in 38 volunteers in a randomized controlled study. The immediate flare and wheal responses to intradermally (i.d.) injected anti-IgE were inhibited by approximately 20 and 30% respectively by a 10 day i.d. pretreatment period with repeated 50 micrograms doses (total 300 micrograms) of betamethasone (P less than 0.01), whereas responses to histamine were not influenced. A single i.d. injection of 50 micrograms betamethasone 24 h prior to anti-IgE challenge attenuated the wheal response (P less than 0.05), whereas injection of the drug 2 h prior to and together with anti-IgE had no influence on the early response. Corresponding LPRs were reduced approximately 30% throughout the observation period of 1-24 h (P less than 0.01). Injecting the drug i.d. 30 min following anti-IgE challenge had no significant influence on the total observation period (1-24 h) of the LPR but antagonized the LPR by 35% at 6-24 h (P less than 0.01). It is concluded that glucocorticoids inhibit IgE-dependent LPRs. When extending the topical pretreatment period with the compounds also the early part of the allergic reaction is attenuated.