LIPOSOMES IN PULMONARY APPLICATIONS - PHYSICOCHEMICAL CONSIDERATIONS,PULMONARY DISTRIBUTION AND ANTIOXIDANT DELIVERY

The application of liposomes for improved drug delivery to the lung is promising. Liposome-mediated pulmonary drug delivery promotes an incr ease in drug retention-time in the lung and more importantly, a reduct ion in extrapulmonary side-effects, invariably resulting in enhanced t herapeutic efficacies. The engineering of an effective liposomal drug formulation for inhalation therapy must take into consideration the le akage problem associated with the nebulization process; vesicle stabil ity and release kinetics within the pulmonary milieu; and, the altered pharmacokinetics of the entrapped drug. The delivery of liposome-entr apped antioxidants via the tracheobronchial route has been found to be very useful in increasing the half-times of the administered agents, thus providing a sustained release effect for prolonged drug action. T he entrapment in liposomes of a-tocopherol, an extremely insoluble but highly effective antioxidant, has been shown to be very effective in ameliorating oxidant-induced injuries in the lung. The use of bifuncti onal liposomes containing two antioxidants have been determined to pro vide excellent resistance to an oxidative challenge and appears to hol d promise for improved clinical applications in antioxidant therapy.