Optimizing delivery of inhaled corticosteroids: matching drugs with devices

Over the past decade, the therapeutic options for delivering inhaled corticosteroids have greatly increased as newer compounds, formulations, and delivery systems have been developed. In the present article, some of the controversies surrounding inhaled steroid delivery systems will be reviewed, concentrating on differences in systemic bioavailability and emphasizing the need to match delivery systems with particular drugs and target populations. The strategies employed to minimize systemic exposure due to absorption of steroid from the gastrointestinal tract include increasing the first pass metabolism of the drug, the use of holding chambers with pressurized metered dose inhalers, and reformulation to create smaller, more respirable, particles. However, because the drugs and devices are not interchangeable, comparisons of the devices based on clinical studies will be confounded by differences in the pharmacology and pharmacokinetics of the drugs. In addition to the interaction of drugs and devices, the needs of different patient populations should influence design of delivery systems. For example, patients without airflow obstruction may have greater systemic exposure compared to those with obstruction, while young children need different delivery systems from adults. In conclusion, no delivery system can be considered to be intrinsically superior to all others. The delivery system should be judged instead by its ability to optimize the pharmacokinetic properties of the drug, most notably oral bioavailability, and by its suitability for the target subpopulation of asthmatics.