Azith Mechanism of Action

Pharmacology: Pharmacodynamics: Azithromycin is an azalide antibiotic, a subclass of macrolide antibiotics. Azithromycin binds to the bacterial 50S ribosomal subunits. It blocks protein synthesis by inhibiting the transpeptidation step of protein synthesis. It leads to inhibit cell growth. Azithromycin usually is bacteriostatic.
Azithromycin is active in vitro against many gram-positive and gram-negative bacteria.
Gram positive aerobic bacteria: Staphylococcus aureus, Streptococcus pyogenes (group A β-hemolytic streptococci), Streptococcus pneumoniae, α-hemolytic Streptococci and other Streptococci.
Erythromycin gram positive bacteria resistance will also resist to Azithromycin include, Streptococcus faecalis (enterococcus) and methicillin-resistant staphylococci.
Gram negative aerobic bacteria: Haemophilus influenzae, Haemophilus parainfluenzae, Moraxella catarrhalis, Legionella pneumophila, Bordetella pertussis, Shigella spp., Vibrio cholerae, Plesiomonas shigelloides, Escherichia coli, Salmonella enteritidis, Salmonella typhi, Aeromonas hydrophila.
Anaerobic bacteria: Bacteroides fragilis, Bacteroides sp., Clostridium perfringens, Peptostreptococcus sp. and Propionibacterium acnes.
Bacterial in sexual transmitted diseases: Chlamydia trachomatis, Treponema pallidum, Neisseria gonorrhoeae and Haemophilus ducreyi.
Opportunistic infections in HIV: Mycobacterium avium-intracellulare complex, Pneumocystis carinii and Toxoplasma gondii.
Other: Borrelia burgdorferi (Lyme disease agent), Chlamydia pneumoniae, Mycoplasma pneumoniae, Mycoplasma hominis, Ureaplasma urealyticum, Campylobacter sp. and Listeria monocytogenes.
Pharmacokinetics: Azithromycin given orally is rapidly absorbed and about 40% bioavailable. Absorption from capsules, not including suspensions, is reduced by food. The peak plasma concentrations occur 2 to 3 hours after an oral dose. Azithromycin plasma concentration following IV administration of a single 500-mg dose of the drug are substantially higher than those following oral administration of the same dose. Peak plasma concentrations occur 1 to 2 hours after intravenous administration. Azithromycin is extensively distributed into the tissues, and tissue concentration subsequently remain much higher than those in the blood. High concentrations are taken up into white blood cells. There is little diffusion into the CSF. Azithromycin crosses the placenta. Small amounts of Azithromycin are demethylated in the liver, and it is excreted in bile mainly as unchanged drug. About 6% of an oral dose is excreted in the urine. While approximately 11% of a 500-mg IV dose of Azithromycin appear in urine as unchanged drug over 24 hours on day 1, and 14% of a 500-mg IV dose of Azithromycin appear in urine as unchanged drug over on day 5. The terminal elimination half-life is about 68 hours.