The effect of BAY u 3405, a thromboxane receptor antagonist, on prostaglandin D2-induced nasal blockage

Background: Nasal lavage and challenge studies in allergic rhinitis implicate prostaglandin (PG) D 2 in the genesis of nasal blockage. PG D 2 is known to act via at least two receptors, the thromboxane prostanoid receptor and the PG D 2 prostanoid (DP) receptor; the lower airway effects are mediated chiefly by the TP receptor. The receptor involved in the genesis of PG D 2 -induced nasal blockage is unknown. BAY u 3405 is a potent selective competitive TP receptor antagonist, which inhibits the lower airway response to PG D 2 , and shifts the dose-response curve to the right by up to 16-fold. Methods: The efficacy of a single oral dose of 20 mg of BAY u 3405 was examined in comparison with PG D 2 nasal insufflation in a randomized, double-blind, placebo-controlled crossover study, with objective measurement of nasal resistance by active posterior rhinomanometry. Results: BAY u 3405 afforded no protection against PG D 2 -induced nasal blockage. Conclusions: This suggests that PG D 2 -induced nasal blockage may be mediated by the DP receptor rather than the TP receptor and that TP receptor antagonists are unlikely to be of benefit in the treatment of allergic rhinitis. In vivo investigation with specific potent DP receptor antagonists is awaited.