Effect of a non‐sedative antihistaminic (loratadine) in moderate asthma

Seventeen patients with perennial asthma, stable on a moderate dose of inhaled steroid, participated in a crossover study comparing the clinical effect of a non-sedative, potent and highly selective H1 antagonist (loratadine 10 mg) with placebo. Each treatment period began with 2 weeks run-in followed by 8 weeks on either antihistamine or placebo. During the 8-week periods inhaled steroid was gradually tapered according to a fixed scheme. One patient was withdrawn from active treatment and three from placebo periods because of decreasing lung function (P greater than 0.1). Among the remaining 13 patients there was a threefold (1.8-4.8) decrease in the bronchial sensitivity to histamine during treatment with antihistamine compared to placebo (P less than 0.01). There was a trend in favour of active treatment with regard to changes in all symptom scores, lung function and use of escape medication, but these differences were not statistically significant. The increase in FEV1 was less than 5% of predicted normal (P less than 0.05). We concluded that the bronchial response to histamine can be attenuated by loratadine, an oral H1 receptor antagonist, but further studies are necessary to assess the clinical usefulness and place of loratadine in the therapy of asthma.