Azithromycin Pharmacodynamics against Persistent Haemophilus influenzae in Chronic Obstructive Pulmonary Disease.

The pharmacodynamic profile of azithromycin against persistent strains of nontypeable Haemophilus influenzae (NTHi) from chronic obstructive pulmonary disease (COPD) patients was characterized. Azithromycin displayed differential concentration-dependent activities (R2 ≥ 0.988); the pharmacodynamic response was attenuated when we compared the "first" and "last" strains of NTHi that persisted in the airways of the same patient for 819 days (the 50% effective concentration [EC50] increased more than 50 times [0.0821 mg/liter versus 4.23 mg/liter]). In the hollow-fiber infection model, NTHi viability was maintained throughout simulated azithromycin (Zithromax) Z-Pak regimens over 10 days.