The effect of desloratadine on eosinophil/basophil progenitors and other inflammatory markers in seasonal allergic rhinitis: a placebo-controlled randomized study.
BACKGROUND
Eosinophil/basophil (Eo/B) progenitors fluctuate in the peripheral circulation during seasonal allergen exposure in atopic subjects. Several drugs have been shown to modulate Eo/B progenitor levels in the peripheral blood but, to date, the possible effect of antihistamines on Eo/B progenitors has not been explored. Our objective was to evaluate whether the antihistamine desloratadine (DL) can modulate peripheral blood Eo/B progenitors or other markers of allergic inflammation.


METHODS
We performed a randomized double-blind placebo-controlled study on the effects of DL on peripheral blood Eo/B progenitors in subjects with symptomatic, seasonal allergic rhinitis during a ragweed pollen season. Forty-five subjects were randomized to treatment for 4 weeks with DL 20 mg daily or placebo.


RESULTS
The expected fall in the number of Eo/B progenitors from baseline to 2 weeks of treatment was seen in the placebo group [median drop of 1.0 colony-forming unit (CFU)/10(6) cells], and was greater than in the DL group (median drop of 0.0 CFU/10(6) cells) (p = 0.013). The change in histamine concentration per colony from baseline to 2 weeks of treatment was lower in the DL group (median decrease of 6.1 pg/colony) compared to placebo (median increase of 1.8 pg/colony) (p = 0.01). An increase in the nasal lavage eotaxin concentration from baseline to 4 weeks of treatment was statistically significant in the placebo group but not in the DL group. Eo/B CFU were not affected by varying in vitro concentrations of DL.


CONCLUSIONS
These results suggest that DL can modulate aspects of allergic inflammation in vivo through mechanisms other than simple blockade of H1 histamine receptors.
Cyr
Michael M
MM
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
Hayes
Lisa M
LM
Crawford
Lynn
L
Baatjes
Adrian J
AJ
Keith
Paul K
PK
Denburg
Judah A
JA
D000293:Adolescent; D000328:Adult; D001491:Basophils / Q000187:drug effects*; D016207:Cytokines / Q000032:analysis; D004804:Eosinophils / Q000187:drug effects*; D005260:Female; D039563:Histamine H1 Antagonists, Non-Sedating / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007958:Leukocyte Count; D017336:Loratadine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D017817:Nasal Lavage Fluid / Q000276:immunology; D011058:Pollen / Q000276:immunology; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology*; D013234:Stem Cells / Q000187:drug effects*
D016207:Cytokines; D039563:Histamine H1 Antagonists, Non-Sedating; D017336:Loratadine; C121345:desloratadine