THE INHALATION DEVICE INFLUENCES LUNG DEPOSITION AND BRONCHODILATING EFFECT OF TERBUTALINE

The development of new inhalation devices for asthma drugs raises the issue of the relationship between pulmonary deposition and therapeutic effect of inhaled drugs in patients with obstructive lung diseases. W e thus conducted a randomized, double-blind and double-dummy, four-per iod crossover study in 13 patients with moderate asthma (mean age 36 y r; FEV(1) 59% of predicted), who inhaled 0.25 and 0.5 mg terbutaline s ulphate on separate occasions either via a pressurized metered dose in haler (pMDI) or Turbuhale(R) (TBH). Pulmonary deposition was 8.1 +/- 2 .7% and 8.3 +/- 2.3%, respectively, of the nominal dose for pMDI and 1 9.0 +/- 7.3%, and 22.0 +/- 8.1% for TBH. The FEV(1) increase after 0.2 5 mg terbutaline sulphate via TBH was significantly greater than after 0.25 mg via pMDI. No significant differences in FEV(1) increase were observed between 0.25 mg via TBH, 0.5 mg via pMDI, or 0.5 mg via TBH. Other lung function variables showed similar dose- and device-related changes. We concluded that: (1) the dose of terbutaline sulphate depos ited in the lungs is dependent on which inhalation system is used; (2) TBH delivers about twice the amount of drug to the lungs as the pMDI; and (3) the observed difference in deposition is reflected in the bro nchodilating effect.