Inhibition of antigen-induced bronchoconstriction by methylprednisolone succinate.

We investigated whether the glucocorticoid methylprednisolone succinate mg/kg) could prevent antigen-induced bronchoconstriction in conscious sheep. Ten allergic ewes were subjected to inhalation challenge with Ascaris suum antigen, with and without methylprednisolone pretreatment, administered intravenously either 20 min or 3 hr before antigen challenge. Antigen challenge alone resulted in increased airflow resistance, pulmonary hyperinflation, and decreases in dynamic lung compliance and arterial oxygen tension. Methylprednisolone administered 20 min before antigen challenge had no effect on these antigen-induced changes. In contrast, administration of methylprednisolone 3 hr before antigen challenge effectively prevented all the responses to antigen challenge. We suggest that pretreatment with glucocorticoids can attenuate airway anaphylaxis if sufficient time is allowed between the pretreatment and the antigen challenge.