RESUMO
BACKGROUND: Histamine is the major mediator of allergic reactions. Newer H1 antihistaminics like levocetirizine, fexofenadine, and desloratadine are used in the treatment of seasonal and perennial allergic rhinitis and urticaria. The ability to block the cutaneous response to intradermal histamine is used to evaluate the potential of antihistamines. AIMS: To compare the potency, onset, and duration of action of the commonly used antihistamines-levocetirizine, fexofenadine, and desloratadine. METHODS: Thirty volunteers were given three single doses of levocetirizine, fexofenadine and desloratadine at weekly intervals. A pretest was performed by using the intradermal histamine prick test. After administration of the drugs, the intradermal test was repeated at (1/2), 1, 2, 3, 6 and 24 h, and the sizes of the wheal were measured. The mean values were taken and were compared by using Levene's t-test. RESULTS: At 30 min, fexofenadine showed a statistically significant suppression of wheal size compared to levocetirizine and desloratadine. Two and three hours after administration, levocetirizine and fexofenadine showed statistically significant inhibition of wheal size while only levocetirizine had this effect after six hours when compared to desloratadine. Desloratadine showed greater inhibition of wheal size at the end of 24 h when compared to levocetirizine and fexofenadine but this was not statistically significant. CONCLUSIONS: Fexofenadine had the earliest onset of action while levocetirizine showed maximum inhibition of wheal response after three and six hours.