Effects of inhaled corticosteroids on the dual asthmatic response

Abstract

Bronchial asthma patients develop various asthmatic response types to allergen challenge, such as immediate asthmatic response (IAR), late asthmatic response (LAR), or dual asthmatic response (DAR), the latter being a combination of an early phase (IAR) and a late phase (LAR). This study was designed to investigate (1) the features of the DAR thus identifying it as either a genuine two-phase compact clinical entity or a simultaneous appearance of two independent asthmatic response types, IAR and LAR, and (2) the protective effects of inhaled budesonide (BUD) on the DAR. Two protection tests (PTs) with BUD and a placebo (PL), in a single dose of 800 micrograms, were performed on 48 DAR patients, divided into four groups. Each test consisted of two treatments, one given 30 minutes before and the other at 1, 2, 3, or 4 hours after the bronchial challenge with allergen. The study design was randomized, double-blind, double-dummy, placebo-matched, crossover. A single dose of inhaled BUD did not affect the early phase (IAR) when applied 30 minutes before the challenge (p > 0.2), whereas it significantly prevented the late phase (LAR) when administered either 30 minutes before (p < 0.001) or up to 4 hours after the allergen challenge (p < 0.05). The different protective effects of BUD on both of the phases of DAR would suggest that this response does not exist as a compact clinical entity, but it may be a manifestation of two independent simultaneous responses, IAR and LAR, because of different immunologic mechanisms. Inhaled corticosteroids in a single dose administered shortly before or up to 4 hours after the allergen exposure contribute significantly to the prevention of the LAR, whereas they are unable to affect the IAR.