Inhaled corticosteroids increase blood neutrophil count by decreasing the expression of neutrophil adhesion molecules Mac-1 and L-selectin.

Objective: The objective was to investigate the effect of commonly used inhaled corticosteroids on white blood cell count (WBC) and to examine the mechanisms involved.

Methods: This randomized comparative study comprised 60 healthy adults. We measured the effects of budesonide (by face mask inhalation or aerosol inhaler), fluticasone (by inhaler), and saline inhalation (control) on WBC and the differential leukocyte count, especially the absolute neutrophil count (ANC). To elucidate the mechanisms involved, we measured the expression of the adhesion neutrophil ligands Mac-1 (CD11b) and L-selectin (CD62L), and granulocyte colony-stimulating factor serum levels.

Results: Six hours after a single-dose inhalation of budesonide, mean increases of 23.4% in WBC (95% confidence interval [CI], 11.3-35.4) and 30.1% in ANC (95% CI, 7.2-53.0) were noted. The percentage of neutrophils increased from 54.6% to 58.1% (P< .001). Inhaled fluticasone increased WBC and ANC by 12.6% (95% CI, 1.5-23.7) and 22.7% (95% CI, 6.2-39.2), respectively (P< .01 for both). The absolute lymphocyte and eosinophil counts did not change significantly from baseline. The expression of Mac-1 and L-selectin decreased by 51.0% (P< .01) and 30.9% (P= .02), respectively, following face mask inhalation of budesonide and by 39.8% (P= .01) and 17.4% (P= .17), respectively, following inhalation of fluticasone. No significant changes in granulocyte colony-stimulating factor levels were noted.

Conclusions: Glucocorticoid inhalation increases WBC by increasing ANC. Reduced neutrophil adhesion to the endothelial surface, mediated by decreased adhesion molecule expression on neutrophils, is a plausible mechanism. Physicians should be aware of the effect of inhaled corticosteroids on WBC, as it may influence clinical decisions, especially in the emergency department.