Pulmonary drug delivery systems for antimicrobial agents: facts and myths

Inhaled antimicrobial agents are used for the treatment of respiratory tract infections due to Gram-negative bacteria, mainly Pseudomonas aeruginosa. The effectiveness of the inhaled antimicrobial therapy is believed to correlate with the delivery system used. The objective of this review was to search for data supporting differentiation in clinical effectiveness between systems used for pulmonary delivery of antibiotics, including delivery using disposable nebulisers and oxygen flow. Published studies in peer-reviewed journals comparing the effectiveness of pulmonary drug delivery systems for antimicrobial agents were retrieved. The studies found were either in vitro or Phase I and Phase II clinical studies. Differences in in vitro parameters may affect the in vivo efficacy of the devices, and in vivo differences may imply differences in clinical effectiveness. The main difference between newer and older devices is the time needed for antibiotic delivery. Interpretation and association with clinical effectiveness is difficult. In conclusion, Phase III clinical trials comparing the clinical effectiveness of delivery systems, including delivery using a hospital's oxygen flow and disposable nebulisers, do not exist. Cost is an important parameter, which may be counterbalanced in cystic fibrosis patients by a better quality of life and a greater adherence to treatment.