Tolerance to the protective effect of salmeterol on allergen challenge can be partially restored by the withdrawal of salmeterol regular treatment.

STUDY OBJECTIVE

To assess whether the withdrawal of salmeterol treatment for 3 days (72 h) can restore its bronchoprotective ability on specific bronchial provocative test (sBPT) with allergen, which was completely lost after 1 week of regular treatment with salmeterol.

STUDY DESIGN

Single-blind design.

PATIENTS AND METHODS

We investigated 10 nonsmoking subjects (8 men and 2 women; mean +/- SD age, 24 +/- 8 years) with mild intermittent allergic asthma in the stable phase of the disease, who were never previously treated with regular beta(2)-agonists. Subjects with a previous positive early airway response (EAR) to a screening allergen challenge were considered. They underwent sBPT with allergen after a single dose of inhaled salmeterol, 50 microg (T(1)), and then underwent sBPT after 1 week of regular treatment with inhaled salmeterol, 50 microg bid (T(2)); after that, they continued inhaled salmeterol treatment for 4 days, and then changed to inhaled salmeterol with placebo (two puffs bid) for 3 days (72 h) and underwent sBPT with allergen after a single dose of salmeterol, 50 microg (T(3)).

RESULTS

EAR to allergen (DeltaFEV(1) > or = 20% with respect to postdiluent value) was completely abolished by a single dose of salmeterol (T(1); protection index [PI] > or = 50% in all subjects), but it was still present after 1 week of regular treatment with salmeterol (T(2); PI < 50% in all subjects). The maximum FEV(1) percentage fall during sBPT with allergen was significantly lower after withdrawal of regular inhaled salmeterol (T(3)) than after regular treatment with salmeterol (T(2)) (mean, 23% vs 29.5%; range, 4 to 41% vs 18 to 49%, respectively; p < 0.05); a similar result was obtained considering the PI of salmeterol on sBPT with allergen (mean, 44% vs 20%; range, 2 to 86% vs - 11 to 49%, respectively; p < 0.05). However, the maximum FEV(1) percentage fall and PI were significantly different in T(3) than after T(1), and only 4 of 10 patients showed in T(3) a PI > or = 50%.

CONCLUSIONS

The bronchoprotective effect of salmeterol on allergen-induced EAR, completely lost after 1 week of regular treatment with salmeterol, may be partially restored by the withdrawal of salmeterol therapy for 3 days (72 h). However, this withdrawal time period is not sufficient to recover the baseline bronchoprotective efficacy of the first dose of salmeterol.