TY - JOUR T1 - Clinical cure rates in patients treated with azithromycin (AZ) for lower respiratory infections (LRTI) caused by AZ-susceptible (AZ-S) and AZ-resistant (AZ-R) organisms: Analysis of phase 3 clinical trials JF - European Respiratory Journal JO - Eur Respir J VL - 44 IS - Suppl 58 SP - P3817 AU - Alan Kaplan AU - George Zhanel AU - Christina Calciu AU - Wolter Kevin Y1 - 2014/09/01 UR - http://erj.ersjournals.com/content/44/Suppl_58/P3817.abstract N2 - Introduction: LRTI are commonly seen in respiratory medicine and include both exacerbations of COPD and community acquired pneumonia. They are often empirically treated with macrolides such as AZ. Resistance rates to macrolides are rising in many parts of the world.Aim: The aim was to determine cure rates in AZ-treated patients with LRTI due to AZ-S and AZ-R organisms in randomized clinical trials (RCT).Methods: 543 patients received AZ in 9 Phase 3 RCTs (1993-2007). Low-level AZ resistance (LLAR) was AZ MIC ≤8 μg/ml; high-level AZ resistance (HLAR) was AZ MIC ≥16μg/ml.Results: 543 LRTI patients had 718 isolates; 174 had an AZ-R organism; 131 had ≥2 pathogens. Cure rates were: 93.4% (507/543) for all LRTI patients; 95.4% (352/369) for AZ-S patients; 89.1% (155/174) for AZ-R patients; 90.7% (97/107) for LLAR and 86.6% (58/67) for HLAR isolates; and 93.9% (123/131) in patients with multiple isolates.Conclusion: AZ cure rates were higher in patients with only AZ-S isolates (95.4%) vs ≥1 AZ-R isolates (89.1%); p=0.006. However, interestingly, no difference was observed for LLAR vs HLAR (p=0.40). AZ is actually an azalide, and is concentrated within lysosomes within circulating white blood cells. Thus serum is not the reservoir supplying tissues and this may underlie the weak relationship between MIC and cure rate. Despite rising resistance to AZ, cure rates are still substantial allowing empirical treatment with AZ to be appropriate for many patients with LRTI. ER -