Pneumozith Mechanism of Action

Pharmacotherapeutic group: Macrolides. ATC code: J01FA.
Pharmacology: Pharmacodynamics: Azithromycin is the first class of antibiotics designated chemically as azalides. Chemically it is derived by insertion of a nitrogen atom into the lactone ring of erythromycin A. The chemical name of azithromycin is 9-deoxy-9a-aza-9a-methyl-9a-homoerythromycin A. The molecular weight is 749.0.
The mode of action of azithromycin is inhibition of protein synthesis in bacteria by binding to the 50s ribosomal subunit and preventing translocation of peptides.
Azithromycin demonstrates activity in vitro against a wide range of bacteria including: Gram-positive Aerobic Bacteria: Staphylococcus aureus, Streptococcus pyogenes (group A beta-hemolytic streptococci), Streptococcus pneumoniae, alpha-hemolytic streptococci (viridans group) and other streptococci, and Corynebacterium diphtheriae. Azithromycin demonstrates cross-resistance with erythromycin-resistant. Gram-positive strains, including Streptococcus faecalis (enterococcus) and most strains of methicillin-resistant staphylococci.
Gram-negative Aerobic Bacteria: Haemophilus influenzae, Haemophilus parainfluenzae, Moraxella catarrhalis, Acinetobacter species, Yersinia species, Legionella pneumophila, Bordetella pertussis, Bordetella parapertussis, Shigella species, Pasteurella species, Vibrio cholerae and Parahaemolyticus, Plesiomonas shigelloides. Activities against Escherichia coli, Salmonella enteritidis, Salmonella typhi, Enterobacter species, Aeromonas hydrophila and Klebsiella species are variable and susceptibility tests should be performed. Proteus species, Serratia species, Morganella species, and Pseudomonas aeruginosa are usually resistant.
Anaerobic Bacteria: Bacteroides fragilis and Bacteroides species. Clostridium perfringens, Peptococcus species and Peptostreptococcus species, Fusobacterium necrophorum and Propionibacterium acnes.
Organism of Sexually Transmitted Diseases: Azithromycin is active against Chlamydia trachomatis and also shows good activity against Treponema pallidum, Neisseria gonorrhoeae, and Haemophilus ducreyi.
Other Organisms: Borrelia burgdorferi (Lyme disease agent), Chlamydia pneumoniae, Mycoplasma pneumoniae, Mycoplasma hominis, Ureaplasma urealyticum, Campylobacter species and Listeria monocytogenes.
Opportunistic Pathogens Associated with HIV Infections: Mycobacterium avium-intracellulare complex, Pneumocystis carinii and Toxoplasma gondii.
Pharmacokinetics: Azithromycin given orally, is rapidly absorbed and about 40% bioavailable. Absorption from capsules but not tablets or suspension, is reduced by food. Peak plasma concentrations occur 2 to 3 hours after an oral dose and 1 to 2 hours after intravenous dosage. However, azithromycin is extensively distributed into the tissues, and tissue concentrations subsequently remain much higher than those in the blood; in contrast to most other antibacterials plasma concentrations are therefore of little value as a guide to efficacy. High concentrations are taken up into white blood cells. There is little diffusion into the CSF when the meninges are not inflamed. Data from animal studies indicate that azithromycin crosses the placenta. Small amounts of azithromycin are demethylated in the liver, and it is excreted in bile mainly as unchanged drug and a number of inactive metabolites have also been detected. About 6% of an oral dose (representing about 20% of the amount in the systemic circulation) is excreted in the urine. The terminal elimination half-life is about 68 hours.