Interaction between corticosteroids and beta-agonists in asthma.

It is often assumed that there is synergy between corticosteroids and beta-agonists, the two drugs most commonly used to treat asthma. A review of clinical studies of the effect of corticosteroids on the response to a beta-agonist finds no evidence to support this assumption except in subjects taking high doses of beta-agonists and with diminished responsiveness to a beta-agonist. There is some evidence that regular beta-agonist therapy may cause a temporary reduction in the efficacy of corticosteroids in asthma, an effect that is seen when the response to the beta-agonist has worn off. Further studies of this effect are required in view of the very widespread concomitant use of the two drugs.