TIME COURSES OF THE ANTI‐ANAPHYLACTIC AND ANTI‐INFLAMMATORY EFFECTS OF DEXAMETHASONE IN THE RAT AND MOUSE

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Abstract
The time course of the activity of dexamethasone has been studied in a variety of anaphylactic and inflammatory reactions in the rat and the mouse. The times of peak activity of dexamethasone, expressed as time between oral dosage and induction of response, and the approximate ED50 values (mg/kg) found were: anaphylactic bronchoconstriction in rats, 12–24 h, ED50 1.8; passive cutaneous anaphylaxis in rats, 6 h, ED50 0.04; cutaneous reactions to histamine in rats, 4 h, ED50 0.01; carrageenin‐induced paw oedema in rats, 4 h, ED50 0.03; pinnal anaphylaxis in mice, 6 h, ED50 0.82; histamine‐induced pinnal reactions in mice, 6 h, ED50 0.05. In rats, the characteristics of the inhibitory effects of dexamethasone indicate a differential activity against anaphylactic and inflammatory reactions and between different types of inflammatory reactions. Possible reasons for these differences are discussed. In mice there was little difference between the inhibition by dexamethasone of cutaneous allergic and histamine‐induced reactions. Pinnal anaphylaxis in mice was potentiated by dexamethasone given 1–2 h before challenge.