Add-on effects of suplatast tosilate in bronchial asthma patients treated with inhaled corticosteroids

Th2 cytokines play an important role in the pathogenesis of asthma. In the present study, we investigated the effect of suplatast tosilate, a selective Th2 cytokine inhibitor, on asthma control, in terms of subjective symptoms and pulmonary function in patients treated with inhaled corticosteroids. Thirty-eight patients with bronchial asthma being treated with inhaled corticosteroids were given suplatast tosilate (100 mg three times daily) for 12 weeks, in a multicenter setting. During the study period, other medications were continued. Morning and evening peak expiratory flow, asthma symptoms, blood eosinophil count and serum IgE levels were monitored. Suplatast tosilate treatment was associated with a significant improvement in mean morning peak expiratory flow (from 295 L/min to 348 L/min, P < 0.01) and evening peak expiratory flow (from 313 L/min to 357 L/min, P < 0.01). The mean daily variation in peak expiratory flow was significantly reduced (from 11.6% to 7.3%, P < 0.01) by suplatast tosilate treatment. The greatest improvement in peak expiratory flow was observed in patients whose blood eosinophil counts were decreased by suplatast tosilate treatment. Treatment with suplatast tosilate improved pulmonary function in patients with bronchial asthma. Our results suggest the therapeutic effects observed may occur through suppression of eosinophilic inflammation.