Identical efficacy of terbutaline multidose dry powder inhaler prior to and after 4 weeks of use by asthmatic patients.

We investigated whether the terbutaline multidose dry powder inhaler (Turbuhaler) has the same efficacy after routine daily use as it has when new. Thirty-three adult asthmatic patients were tested on two occasions. The bronchodilatory effect of inhalations of 0.5, 0.5 and 1.0 mg terbutaline at 40-min intervals from the same device was determined prior to and after using the device at least three times a day for 4 weeks. When tested for the second time, 116-186 doses had been inhaled. Although baseline forced expiratory volume in 1 s (FEV1) was slightly higher after the 4-week treatment period, the bronchodilatory effect of the inhaled terbutaline doses was identical. We conclude that the multidose dry powder inhaler is as effective in delivering terbutaline after a period of routine daily use as it is when new.