FUTURE-PROSPECTS FOR PULMONARY DELIVERY OF DRUGS

The requirement to obtain safe replacement propellants for ozone deple ting chlorofluorocarbons has prompted the pharmaceutical industry to r e-evaluate the available techniques for optimizing pulmonary delivery of drugs via aerosol formulations. The safety and toxicity profiles of two new hydrofluorocarbons, presently being examined by two internati onal consortia of pharmaceutical companies, are at present looking fav ourable, although long term evaluation studies are still in progress. Extensive and complex reformulation of pressurized multidose inhalers still remains to be carried out before commercially available products will appear. Technological development of nebulizers is also proceedi ng quickly, and prototype electronically controlled, pocket-sized batt ery-powdered ultrasonic devices are already available. A third strateg y has been to re-examine dry powder inhalers with a view to maximizing the respirable fraction. Three interdependent factors determine the d eposition profile of drugs emerging as an aerosol from a dry powder in haler, namely the patient, the device and powder formulation. New dry powder inhaler devices will aim to maximize turbulence within the inne r air passages, without inducing marked resistance to inspired air. Se veral formulation variables remain to be fully investigated if deposit ion within the lung is to be improved dramatically above the 10.0% (ad ministered dose) currently attainable. Finally, it is essential that i n vitro methodology evolves which enables an accurate estimate to be m ade of respirable fraction, so that the effects of formulation and dev ice modifications can be determined without the need to resort routine ly to expensive volunteer trials.