Azithromycin Dihydrate

Azithromycin displays a similar spectrum of antimicrobial activity. Azithromycin is marginally less active than erythromycin in vitro against Gram-positive organisms, although this is of doubtful clinical significance as susceptibility concentration fall within the range of achievable tissue Azithromycin concentrations. The mean MIC90 of Azithromycin against erythromycin susceptible/βL-ve strains, Streptococcus strains and NS (not selected for antimicrobial sesitivity)/erythromycin susceptible strains is 0.63, 0.35, and <0.27 mg/L, respectively. In contrast, Azithromycin appears to be more active than erythromycin against many Gram-negative pathogens and several other pathogens, notably Haemophilus influenza (MIC90, 1.34 mg/L), H. parainfluenzae(MIC90, 1 mg/L), Moraxella catarrhalis (MIC90, <0.1 mg/L), Neisseria gonorrhoeae (MIC90, 0.25 mg/L), Ureaplasma urealyticum, Bordetella spp (MIC90, 0.03-0.24 mg/L) and Borrelia burgdorferi. Azithromycin is also activity against clinical isolates of anaerobic bacteria Gram-positive cocci and propionibacterium acnes with MIC90 of 2.3, 0.03 mg/L. Like erythromycin and other macromycin, the activity of Azithromycin is unaffected by the production of β-lactamase. However, erythromycin-resistant organisms are also resistant to Azithromycin. ^[1]