The effect of characteristic of pulmonary delivery devices and drug formulation on lung deposition and efficacy of inhalant therapy

The pulmonary drug delivery shows numerous advantages over other routes of administration. The major advantage is the high drug concentration in the lungs and low concentration in serum. Consequently, the systemic side effects especially due to corticosteroid therapy are minimized. The major problem by the use of various inhalant devises is the proper technique of inhalation. Thus when selecting an aerosol delivery device for patients with asthma and COPD the ability to reach the optimal inspiratory flow should be evaluated. This is basic for the effective drug deposition in the lung. It has been shown for the dry powder inhalers (DPI) that the higher the resistance of the device, the more difficult it is to generate an inspiratory flow great enough to achieve the maximum dose from the inhaler. Thus the proportions of patients capable to achieve the optimal drug delivery are different for various DPI. The resistance of the device as well as the patients ability to use the selected device correctly determine the delivered drug dose and aerosol formulation, which in turn affect both total and regional drug deposition in the lungs. Consequently, the same drug at the same nominal dose delivered from different devices or in different formulations may not be bioequivalent.