Salbutamol pMDI gives less protection to methacholine induced airway obstruction than salbutamol via spacer or DPI

Background: Inhalation device and inhalation technique influence the deposition of drug in the lung. This study evaluated the efficacy of salbutamol as a bronchoprotective agent administered via Diskus, Turbuhaler, pMDI or pMDI+Volumatic against methacholine-induced bronchoconstriction. Methods: Twenty stable asthmatics participated in this open randomised comparison of the protective effects of 200 μg salbutamol, administered via the various inhalation devices on methacholine-induced airway obstruction, with respect to pulmonary function and dyspnoea sensation. The inhalation technique was controlled by measuring the peak inspiratory flow (and actuation time, in the case of pMDI and Volumatic) through the device, during inhalation. Results: Inhalation of salbutamol increased the provocative dose of methacholine by 1.2 doubling doses (dd) for pMDI, 1.9 dd for Diskus, 2.3 dd for Turbuhaler and 2.5 dd for Volumatic. Salbutamol via pMDI provided less protection from methacholine-induced airway obstruction than did salbutamol administered via Diskus, Turbuhaler or Volumatic (P<0.05). The inadequate pMDI use of 70% of our patients might contribute to a lower deposition of drug in the central airways, resulting in the lower protective effect. However, the PC20_FEV1 of the adequate- and inadequate pMDI users showed no significant difference. Conclusion: Salbutamol administered via pMDI gave less protection from methacholine-induced bronchoconstriction than did salbutamol via Diskus, Turbuhaler or Volumatic. This study suggests that the pMDI may be less suitable for protecting a patient against bronchoconstriction due to airway hyperresponsiveness.

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