In vitro comparative dynamics of modified-release clarithromycin and of azithromycin
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Updated: Oct 13, 2026

High Throughput, Real-time, Dual-readout Testing of Intracellular Antimicrobial Activity and Eukaryotic Cell Cytotoxicity
Published on: November 16, 2016
F Scaglione1, G Demartini, S Dugnani
1Department of Pharmacology, University of Milan, Italy.
Abstract:
Antibacterial kinetics of modified-release clarithromycin (CLA) and azithromycin (AZI) against respiratory tract pathogens were compared in relation to their pharmacokinetic profile. The study was carried out in three strains of Streptococcus pneumoniae, group A beta-hemolytic Streptococcus pyogenes, Moraxella catarrhalis and Haemophilus influenzae, respectively, exposed to concentration gradients of CLA and AZI simulating human serum pharmacokinetics after administration of 500 mg p.o. in a single dose. Bactericidal kinetics were assessed by counting the number of survivors before each change in concentration over a period of 36 h. The minimal inhibitory concentrations (MICs) of CLA and AZI were evaluated at time 0 and after 36 h of exposure to antibiotics in the surviving organisms. The results showed that CLA and AZI, in the experimental conditions adopted, had different antibacterial kinetics. Moreover, the addition of the 14-OH metabolite of CLA at the same concentrations reached in human serum exerted a bactericidal effect against two strains of H. influenzae resistant to CLA and AZI. An increase in MICs was observed against S. pyogenes and H. influenzae, with higher values for AZI.
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