The onset of effect of the H1-antagonist acrivastine ("Semprex") assessed by histamine bronchial challenge in volunteers.

The onset of effect of acrivastine, a new H1-antagonist, has been assessed using antagonism of histamine-induced bronchoconstriction in sensitive volunteers. Acrivastine administered 30, 45, 60 or 90 min before challenge produced a right-shift of the histamine dose-response curve of at least 8-fold indicating that a clinically desired degree of H1-antagonism was present within 30 min of ingestion of the recommended therapeutic dose.