Lack of effect of loratadine on moderate to severe asthma

Antihistamines have been shown to be effective in patients with allergic asthma, but their role in chronic and more severe asthma is uncertain.

To evaluate whether loratadine, a selective H1 receptor antagonist, given as an adjunct to standard asthma medication would have any effect in patients with moderate-to-severe asthma.

Thirty-five patients with moderate-to-severe asthma, most receiving inhaled steroids, were enrolled in this double-blind, crossover study. In addition to their maintenance therapy patients received either loratadine, 20 mg once daily, or placebo for 4 weeks before crossing over to the other preparation for a further 4 weeks. Variables of efficacy were daily and nocturnal respiratory symptoms, lung function (PEF, FEV1, FVC), and bronchodilator use.

Three subjects were withdrawn from the study because of deteriorating asthma. There was a trend in favor of loratadine treatment with regard to global assessment of drug efficacy but the difference was not statistically significant. There was no objective improvement in asthma control comparing loratadine with placebo but if each treatment week were compared with the run-in period, PEF was significantly (P < .01) improved during the initial phase of loratadine treatment. This effect gradually decreased with time, suggesting tolerance to any bronchodilatory effect of the antihistamine.

Loratadine, given as an adjunct to standard asthma therapy, has little if any role to play in the treatment of moderate-to-severe asthma.