A comparison of central and peripheral effects of cetirizine and loratadine.

In a double-blind, crossover, randomized clinical pharmacological study performed on 10 healthy volunteers, peripheral and central effects of 10 mg cetirizine and 10 and 40 mg loratadine were compared. Cetirizine (10 mg) significantly (P less than 0.001) inhibited 10 or 100 mg/ml histamine-induced weals 2 and 6 h after drug intake. Cetirizine was more potent than 10 mg loratadine after 2 and 6 h, and was even more potent than 40 mg loratadine after 6 h. Neither drug affected subjective evaluation of central effects and cetirizine was completely devoid of electro-encephalographic (EEG) changes, whereas 10 and 40 mg loratadine induced only slight and limited EEG changes.