Consistency and efficacy of cetirizine (10 mg) versus ebastine (20 mg) at 4 h on skin reactivity

Objective: We compared the consistency and efficacy of the two antihistamin es, cetirizine (10 mg) and ebastine (20 mg) on histamine skin reactivity 4 h after treatment. Methods: Twenty-four healthy volunteers participated in a randomised double -blind cross-over study. The areas of wheals and flares induced by increasi ng (0, 5, 10, 50, 100, 200, 300 mg/ml) histamine concentrations, administer ed by prick tests, were measured before and 4 h after intake of cetirizine or ebastine. Results: Before treatment, concentration-response curves were similar and t hreshold concentrations identical (0.57 mg/ml and 0.57 mg/ml for cetirizine and ebastine, respectively). Both treatments exerted a significant effect. However, cetirizine was significantly more efficient than ebastine 20 mg ( P < 0.01 both for wheals and flares). After cetirizine, the threshold conce ntration inducing a 3-mm(2) wheal was significantly higher (266 mg/ml) than after ebastine (77 mg/ml) (P < 0.01), and total inhibition of the wheal wa s obtained in 18 of 24 patients for cetirizine and in 4 of 24 for ebastine (P < 0.001). The variation coefficient for the wheal reaction was 31% for c etirizine and 159% for ebastine, indicating a much lower variability after cetirizine. Conclusion: Our study shows clearly that the efficacy of a single therapeut ic dosage of cetirizine is greater and consistently better than that of eba stine for suppression of cutaneous reactivity to histamine 4 h after treatm ent in healthy volunteers. The need for ebastine to metabolise into the act ive carebastine might explain this difference.