Effect of inhaled terbutaline on platelet activity in bronchial asthma.

Thirty five young subjects with long standing bronchial asthma were studied for the effects of terbutaline misthaler (500 micrograms) during acute asthma. Bronchodilators were omitted for a day before the test. Ten matched controls were also studied. In all subjects, basal IgE level (ELISA), pulmonary parameters (FVC, FEV, PEFR, FEF 25-75 and FEF 75-85) and platelet activity, (platelet clumping/150 WBC on smear, platelet adhesiveness, blood recalcification time and kaolin clotting time for platelet factor3) were compared. During acute asthma, the subjects displayed IgE levels > or = 500 IU/ml (n = 33), activation of clotting (n = 30) and eosinophilia > or = 450/cmm (n = 28). These changes were not seen in normal controls. Terbutaline resulted in a reversal of airway obstruction, mainly of small airways, while the platelet hyperactivity and blood hypercoagulability were rectified (P < 0.001). It is concluded that platelet activity increases in acute asthma and is corrected by inhaled terbutaline concomittant with the relief of bronchospasm.