Effect of oral prednisolone on the bronchoprotective effect of formoterol in patients with persistent asthma

Tolerance to the bronchoprotective effects by long-acting beta (2)-agonists (LAB) in patients with asthma is not prevented by inhaled corticosteroids (ICS). This study examined whether oral prednisolone can restore the bronch oprotective effects of formoterol in 24 patients with persistent asthma alr eady treated with ICS (at least 800 pg budesonide(.)day(-1) or equivalent) and LAB, using a parallel-group design. During a 2-week run-in period and during the study, patients used formotero l 12 pg twice daily by Turbuhaler (R), instead of their own LAB. At baselin e and at the end of 7-days treatment with oral placebo or prednisolone (30 mg(.)day(-1)), provocative concentration of histamine causing a 20% fall in forced expiratory volume in one second (PC20 histamine) was measured on tw o separate days after randomized single-dose inhalation of placebo (postP) or formoterol (postF). In addition, PC(20)postF was measured 24 h after sta rting oral treatment. The protective effect by formoterol at baseline and d uring treatment was calculated as the difference between the logs of PC(20) postP and PC(20)postF. The mean +/- SEM in doubling dose (DD) bronchoprotective effect at baseline was 0.8 +/- 0.4 DD in the placebo group and 1.0 +/- 0.4 DD in the predniso lone group. At the end of the treatment period, the protective effect chang ed to 1.0 +/- 0.5 DD and 0.8 +/- 0.6 DD in the placebo and prednisolone tre ated groups, respectively. This change was not different between the groups (p > 0.4). In conclusion, the bronchoprotective effect by formoterol is not influenced by 1 week prednisolone treatment in patients with asthma who are using reg ular inhaled corticosteroids and long-acting beta (2)-agonists. These findi ngs indicate that tolerance to long-acting beta (2)-agonists cannot be rest ored by oral steroid therapy.