Drug Groups

approved

Description

Azithromycin is a semi-synthetic macrolide antibiotic of the azalide class. Like other macrolide antibiotics, azithromycin inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit of the bacterial 70S ribosome. Binding inhibits peptidyl transferase activity and interferes with amino acid translocation during the process of translation. Its effects may be bacteriostatic or bactericidal depending of the organism and the drug concentration. Its long half life, which enables once daily dosing and shorter administration durations, is a property distinct from other macrolides.

Indication

For the treatment of patients with mild to moderate infections caused by susceptible strains of the designated microorganisms in the specific conditions: H. influenzae, M. catarrhalis, S. pneumoniae, C. pneumoniae, M. pneumoniae, S. pyogenes, S. aureus, S. agal

Pharmacology

Azithromycin, a semisynthetic antibiotic belonging to the macrolide subgroup of azalides, is used to treat STDs due to chlamydia and gonorrhea, community-acquired pneumonia, pelvic inflammatory disease, pediatric otitis media and pharyngitis, and Mycobacterium avium complex (MAC) in patients with advanced HIV disease. Similar in structure to erythromycin. azithromycin reaches higher intracellular concentrations than erythromycin, increasing its efficacy and duration of action.

Toxicity

Potentially serious side effects of angioedema and cholestatic jaundice were reported

Affected Organisms

Biotransformation

Hepatic. In vitro and in vivo studies to assess the metabolism of azithromycin have not been performed.

Absorption

Bioavailability is 37% following oral administration. Absorption is not affected by food. Azithromycin is extensively distributed in tissues with tissue concentrations reaching up to 50 times greater than plasma concentrations. Drug becomes concentrated within macrophages and polymorphonucleocytes giving it good activity against Chlamydia trachomatis.

Half Life

68 hours

Protein Binding

Serum protein binding is variable in the concentration range approximating human exposure, decreasing from 51% at 0.02 µg/mL to 7% at 2 µg/mL.

Elimination

Biliary excretion of azithromycin, predominantly as unchanged drug, is a major route of elimination.

Distribution

* 31.1 L/kg

Clearance

* apparent plasma cl=630 mL/min [following single 500 mg oral and i.v. doses]

References

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