Background: In atopic asthma there is strong evidence of eosinophils playing an active role in pathogenesis. Some investigations demonstrated that eosinophil cationic protein (ECP) serum levels increased in atopic patients with asthma during pollen season.
Objective: The aim of the study was to evaluate the effects of short-term (1 week) beta 2-agonist treatment on lung function and eosinophil activity in asthmatic patients.
Methods: We used an open, randomized, cross-over design to compare the effects of salbutamol (200 micrograms q.i.d.) and salmeterol (50 micrograms b.i.d.) on peak expiratory flow rate (PEFR), blood eosinophil count and serum levels of ECP as a measure of eosinophil activity in 20 mild atopic asthmatics.
Results: Morning and evening PEFR values were both significantly higher during salmeterol treatment than during the salbutamol period. Conversely, both morning and evening daily asthma symptom scores were significantly lower during salmeterol treatment compared with those recorded during the salbutamol period. The mean basal eosinophil blood count on salmeterol treatment (601 +/- 189 mm3) was not higher than the mean count on salbutamol treatment (612 +/- 204 mm3). After both treatments the mean eosinophil blood counts were unchanged (619 +/- 189 mm3 and 576 +/- 212 mm3, respectively). No significant differences in blood eosinophil counts were observed between or within treatments at any time. No significant difference was observed in baseline mean ECP serum concentration (43.8 +/- 26.3 micrograms/L on salmeterol treatment and 41.7 +/- 29.8 micrograms/L on salbutamol treatment, respectively). After salmeterol treatment the mean ECP serum concentration had fallen significantly to 20.9 +/- 18.6 micrograms/L (P < 0.01), whereas after salbutamol treatment it was unchanged (42.0 +/- 25.1 micrograms/L). Salmeterol treatment produced a decrease in ECP serum levels without any changes in blood eosinophil count.
Conclusion: This study demonstrates that salmeterol affords a significant improvement in asthma control during the pollen season, measured by both subjective and objective parameters, compared with salbutamol. This greater efficacy may be related to inhibition of eosinophil degranulation during the pollen season.