Objective: Emedastine is a novel H1-receptor antagonist with pre-clinically well-documented anti-allergic effects. Here, we set out to study the relationship between emedastine pharmacokinetics and the suppressive effect on histamine-induced wheals and flares, and to compare these effects to placebo and cetirizine.
Methods: Emedastine (4 mg q.d.), emedastine (2 mg b.i.d.), cetirizine (10 mg q.d.) and placebo were administered to healthy volunteers in a double-blind, cross-over fashion. On day 1 and day 5 (steady state) following drug administration, wheals and flares were induced by skin-prick testing with 1 mg ml(-1) or 10 mg ml(-1) histamine.
Results: Following the administration of 4 mg emedastine q.d., mean area under the concentration-time curve (AUC)0-24 values of 34.49 +/- 24.07 ng h ml(-1) and 47.05 +/- 36.12 ng h ml(-1) were attained on day 1 and day 5, respectively. Following the administration of emedastine (2 mg b.i.d.) mean AUC0-24 values were 29.75 +/- 19.92 ng h ml(-1) and 46.13 +/- 38.50 ng h ml(-1) on day 1 and day 5, respectively. Histamine-induced wheals and flares were significantly more effectively suppressed by emedastine and cetirizine than placebo. At pharmacokinetic steady-state levels, no significant difference could be found in the potency between cetirizine and emedastine (2 mg b.i.d.).
Conclusion: Emedastine displays pharmacodynamic properties comparable with cetirizine and therefore qualifies as a safe and alternative compound with H1-receptor antagonist properties. Additional larger studies may be needed to substantiate potential benefits of cetirizine over emedastine after single-dose administration.