Protective Effect of Loratadine on Late Phase Reaction Induced by Conjunctival Provocation Test

Abstract

The protective effect of Loratadine, a new generation, non-sedating antihistamine, on clinical and cellular events during the early phase reaction (EPR) and late phase reaction (LPR) of the allergen-specific conjunctival provocation test (CPT) was assessed out of the pollen season in 20 seasonally allergic rhino-conjunctivitis patients. After a screening CPT, selected patients were randomized to Loratadine (10 mg OD) or matching placebo for 7 days. CPT was repeated following treatment. Clinical and cellular responses were evaluated by a symptom score and cell counting in conjunctival scrapings before, and 30 min and 6 h after challenge with allergen (one eye) or placebo (control eye). Conjunctival symptom severity following CPT was reduced at 30 min (EPR) and 6 h (LPR) after CPT in the Loratadine group compared to placebo group (p < 0.01), as was the total number of inflammatory cells (p < 0.001). In conclusion, Loratadine protects against the clinical and cellular EPR and LPR events consequent to CPT, showing antiallergic properties.