• allergic rhinitis;
  • desloratadine;
  • mannitol;
  • montelukast;
  • nasal hyper-reactivity

Aims  It is unclear as to which mediators are involved in mediating the response to nasal mannitol challenge, a novel osmotic stimulus.

Methods  A double-blind, randomized, placebo-controlled, crossover design was employed. Nine patients with allergic rhinitis were randomized to receive a single-dose of desloratadine 5 mg, montelukast 10 mg or placebo, and underwent nasal mannitol challenges with nasal peak inspiratory flow recordings over 60 min. The change in peak nasal inspiratory flow was calculated as percentage change from baseline as the peak response and area under the time–response curve (AUC).

Results  Desloratadine and montelukast conferred a significant degree of protection compared to placebo for peak and AUC response, but there were no significant differences between the two drugs. For the peak response as percentage fall, the mean difference (95% CI) vs placebo was 27.7 (8.0, 47.4)% for desloratadine and 17.6 (1.9, 33.3)% for montelukast.

Conclusions  Our results suggest that histamine and cysteinyl-leukotrienes are involved in mediating the response to nasal mannitol in allergic rhinitis.