Comparison of bactericidal activity after multidose administration of clarithromycin, azithromycin, and ceruroxime axetil against Streptococcus pneumoniae.

The objective of this study was to compare the duration of serum bactericidal activity (SBA) for clarithromycin, azithromycin, and cefuroxime axetil in 12 young healthy volunteers after 5 days of therapy (dosed to steady-state) against two strains each of penicillin (PCN)-susceptible, -intermediate, and -resistant Streptococcus pneumoniae. This was a randomized, 3-way crossover study. All isolates were susceptible to clarithromycin (MICs 0.125 mg/l) and azithromycin (MICs 0.25-0.5 mg/l), while cefuroxime axetil susceptibilities correlated with PCN. Results showed that SBA was maintained for 100% of the dosing interval for clarithromycin and 50-100% for azithromycin regardless of PCN susceptibility when standard doses were employed. Cefuroxime axetil was active only against the PCN-susceptible isolate for 50% of the dosing interval, indicating that it should only be used for PCN-susceptible S. pneumoniae.