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

The inhalation of aerosolised drug has become a well established treat ment modality in conditions such as asthma. The pressurised metered-do se inhaler (MDI) is still the most commonly prescribed inhalation syst em, despite a number of associated disadvantages. The requirement to r eplace 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, th e efficiency of delivery is currently not high, with in some cases onl y approx. 10% of the inhaled dose of the drug reaching the alveoli. Th e site of deposition and the deposition patterns of the inhaled aeroso l from DPIs is influenced by two major interdependent factors: (a) the patient (anatomical and physiological aspects of the respiratory trac t as well as mode of inhalation) and (b) the physical properties of th e aerosol cloud (attributable either to the dry powder formulation or the design of the DPI devices). Mole recently, as engineers have contr ibuted to the design of DPI devices encouraging results have been obta ined in clinical trials performed to compare the efficacy and acceptab ility of DPI with other drug delivery systems. Undoubtedly more cross- disciplinary collaboration of this kind will lead to further improveme nts in drug delivery from such formulations and may ultimately provide a feasible means of presenting drugs of peptide origin to the body fo r systemic therapeutic action.