DRUG-DELIVERY TO THE RESPIRATORY-TRACT USING DRY POWDER INHALERS

The inhalation of aerosolised drug has become a well established treatment modality in conditions such as asthma. The pressurised metered-dose inhaler (MDI) is still the most commonly prescribed inhalation system, despite a number of associated disadvantages. The requirement to replace the ozone-depleting chlorofluoro-carbon propellants, present as an integral part of all MDIs, has led to the pharmaceutical industry re-evaluating the potential of dry powder inhalers (DPIs). However, the efficiency of delivery is currently not high, with in some cases only approx. 10% of the inhaled dose of the drug reaching the alveoli. The site of deposition and the deposition patterns of the inhaled aerosol from DPIs is influenced by two major interdependent factors: (a) the patient (anatomical and physiological aspects of the respiratory tract as well as mode of inhalation) and (b) the physical properties of the aerosol cloud (attributable either to the dry powder formulation or the design of the DPI devices). Mole recently, as engineers have contributed to the design of DPI devices encouraging results have been obtained in clinical trials performed to compare the efficacy and acceptability of DPI with other drug delivery systems. Undoubtedly more cross-disciplinary collaboration of this kind will lead to further improvements in drug delivery from such formulations and may ultimately provide a feasible means of presenting drugs of peptide origin to the body for systemic therapeutic action.