Pharm 101: Azithromycin

Class

Macrolide antibiotic

Pharmacodynamics
  • Inhibits bacterial protein synthesis by binding to 50S ribosomal RNA
Pharmacokinetics
  • PO or IV administration
  • Rapidly absorbed orally
  • Penetrates into most tissues (except CSF) and phagocytic cells extremely well
    • Tissue concentrations exceed serum concentrations 10-100 fold
    • Drug is slowly released from tissues (tissue half life 2-4 days), elimination half-life thus ~3 days
    • Permits infrequent dosing and short courses of treatment
  • No CYP interactions, unlike erythromycin and clarithromycin
Antimicrobial activity of macrolide antibiotics
  • Gram positive organisms e.g. pneumococci, strep, staph
  • Mycoplasma pneumoniae, L pneumophila, Chlamydophila pneumoniae, Listeria monocytogenes
  • Gram negative organisms e.g. neisseria, bordatella pertussis, campylobacter
  • Treponema pallidum
  • Azithromycin specifically:
    • Highly active against Chlamydophila sp.
    • Active against Toxoplasma gondii
    • Slightly less active against staph and strep
    • Slightly more active against H influenzae
Adverse effects
  • Prolonged QT interval
Further reading
References
Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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