Background Loratadine and cetirizine are new generation antihistamines, which are clinically effective in the treatment of allergic rhinitis.
Objective The aim of the study was to evaluate antiallergic activity of loratadine compared with cetirizine, over a 2 week period under natural allergen exposure, in a double-blind parallel groups, randomized, controlled trial.
Methods Twenty patients, sensitized to grass and/or Parietaria pollen, were subdivided into two groups, one receiving loratadine the other cetirizine respectively. Both were dosed at 10 mg/day. Evaluated parameters were: clinical symptoms, nasal inflammatory cell (such as neutrophil, eosinophil and metachromatic cells) counts, ICAM-1 expression on nasal epithelial cells, and nasal mediators (e.g. histamine, ECP, EPO and MPO).
Results Loratadine and cetirizine significantly improved symptoms (P < 0.002), significantly reduced eosinophil (P < 0.016) and metachromatic cell (P < 0.01) infiltration, levels of ECP (F < 0.002), EPO (P < 0.006) and histamine (P < 0.01) and ICAM-1 expression on nasal epithelial cells (P < 0.02). No difference was demonstrated between the two drugs.
Conclusion The antiallergic activity of loratadine and cetirizine is documented by their actions on the inflammatory and clinical parameters, especially ICAM-1 modulation.