Pharmacokinetics of antibiotics in the lungs

This paper reviews current knowledge on the relationship between local penetration or antibiotics and therapeutic efficacy in pulmonary and bronchial infections. The antimicrobial drug concentration at the site of infection is supposedly determinative for the efficacy of the antibiotic treatment but the number of studies in respiratory infections supporting this hypothesis is limited. The mechanisms responsible for the pulmonary deposition or orally or systemically administered antibiotics include passive diffusion, active transport, bulk flow and permeation. The penetration of antimicrobial drugs into the respiratory tract is influenced by both host-related factors, such as inflammation or mechanical injury, and drug-related factors, such as molecular weight. In addition, local bio-inactivation can occur. The final bioactive antibiotic concentration at the site of the respiratory infection is, therefore, the result or a very complex dynamic process. Different sampling and measuring methods have been used for the assessment of antibiotic concentrations at the site of respiratory infections. Concentrations in sputum, bronchial secretions and biopsy specimens have been correlated with serum concentrations and clinical outcome. Bronchoalveolar lavage could be a promising technique for evaluating antibiotic drug concentrations in alveolar lining fluid. For many antibiotics, data concerning penetration and pharmacokinetic behaviour in the respiratory tract are lacking.