Inhaled beclomethasone dipropionate reverts tolerance to the protective effect of salmeterol on allergen challenge

Study objective: One week of regular treatment with salmeterol can induce t olerance to the protective effect of a beta(2)-agonist on early airway resp onse to allergen (EAR). The objective was to assess whether inhaled cortico steroids revert tolerance to salmeterol. Study design: The study had a rand omized, double-blind, placebo-controlled design. Patients and methods: Twelve subjects with mild allergic asthma and positiv e result of specific bronchial provocation test (sBPT) to allergen underwen t three sBPTs, separated by 1 week. sBPT was done in all subjects after a s ingle dose (T-1) and after 1 week of regular treatment with inhaled salmete rol (50 mu g bid) (T-2) in order to induce tolerance. Subjects were then ra ndomized to receive either the same dose of salmeterol + beclomethasone dip ropionate (BDP, 500 mu g bid) (group 1, n = 6) or placebo + BDP (group 2, n = 6) for 1 week before sBPT (T-3). Results: After a single dose of salmeterol (T-1), all subjects were protect ed against EAR, whereas after 1 week of regular treatment, the protective e ffect of salmeterol was totally or partially lost (T-2). Maximum FEV1 perce nt fall (Max Delta FEV1%) after allergen inhalation was significantly highe r at T-2 than at T-1. All subjects except one of group 1 were protected aga inst EAR after salmeterol + BDP (T-3), and Max Delta FEV1% at T-3 (median, 12%; range, 4 to 6%) was significantly lower than T-2 (median, 22%; range, 12 to 43%; p < 0.05 by Wilcoxon test). Subjects of group 2 did not show any significant protection against EAR after placebo + BDP treatment (T-3) Max Delta FEV1% at T-2 (median, 31%; range, 9 to 40%) and T-3 (median, 31%; ra nge, 3 to 42%; not significant). Conclusions: In conclusion, the addition of inhaled BDP partially restored the bronchoprotective effect of salmeterol on allergen challenge that was l ost after 1 week of regular treatment with salmeterol alone. This ability o f BDP in reverting tolerance cannot be ascribed to a direct effect of corti costeroids per se on allergen challenge in this group of asthmatics.