1. Mechanism of Action
    Inhibition of protein synthesis by binding to Domain V of the 13s rRNA which is a part of the 50S subunit.

    More specific to bacteria which reduce toxicities.
  2. Static vs. Cidal
    Both Static and Cidal

    Depends on Dose, Site and Organism
  3. Spectrum of Activity (Gram Positive)
    S. Aureus (Not drug of choice, resistance has become common)

    • S. Pneumoniae (Respirtory tract infections - CA)
    • Variable activity against S. pyogenes and Viridans strep

    Poor against Enterococcus
  4. Spectrum of Activity (Gram Negative)
    • H. pylori
    • M. catarrhalis
    • H. flu (Erythromycin is not reliable)
    • Campylobacter jejuni
    • N. gonorrhoeae
    • N. meningitidis
    • Bordetella pertussis
    • Poor Enterobacteriaceae coverage
  5. Spectrum of Activity (Miscellaneous)
    Poor anaerobic coverage

    Excellent coverage of Atypicals
  6. Mechanisms of Resistance
    • Efflux
    • Mediated by mefA/E gene

    • Target site modification
    • Mediated by erm gene
  7. Erythromycin
    • Bioavailability: 18-45%
    • Metabolism: Hepatic
    • Elimination: Partially unchanged in bile
    • Half Life: 1-2 h
    • Generally food decreases absorption
    • Inhibitor os CYP enzymes (Drug interactions)
  8. Clarithromycin
    • Bioavailability: 50-55%
    • Metabolism: Hepatic
    • Elimination: Primarily Renal
    • Half Life 4-7 h
    • May be taken with or without food. (Decreases GI side effects)
    • Inhibitor of CYP enzymes (Drug Interactions)
  9. Azithromycin
    • Bioavailability: 35-40%
    • Metabolism: Hepatic
    • Elimination: Unchanged in bile, 20% unchanged in urine)
    • Half-Life: 29-96 h
    • Take with or without food. (Capsule should be no food)
    • Has high concentrations as site of infection. As a result serum conc. suffer so use in primary bacteremia is questionable.
  10. Distribution
    • Excellent tissue penetration
    • Poor CSF penetration
    • Produce high intracellular concentrations in several different cells such as WBC
  11. Metabolism
    CYP450 system substrates.
  12. Drug Interactions
    • Theophylline
    • Type I antirrhythmic drugs
    • Antacids: Dec absorption of azithromycin
    • Warfarin
    • Caramazepine (Inhibits it's metabolism)
    • Digoxin (inc conc. levels)
    • Cyclosporine (inc. conc. levels)
  13. Therapeutic Uses
    • Respiratory tract infections
    • STDs
    • Peptic Ulcer Disease
    • Cat Scretch Fever
    • Whooping Cough
    • Lyme Diseases
    • Mycobacterium avium complex (MAC)
  14. Adverse Effects
    • Gastrointestinal
    • Mild elevation of liver enzymes
    • Headachle or Dizziness
    • Tinnitus
    • Hypersensitvity Reactions (Rare)
    • Cardiovascular
  15. Pregnancy
    • Azithromycin and Erythromycin: Category B
    • Clarithromycin: Category C
  16. Addition Activity (In addition to antimicrobial effect)
    • Limits production of pro-inflammatory cytokines
    • Reduce neutrophil chemotaxis
    • Decrease sputum and mucus production
    • Used in Cystic Fibrosis
    • Diabetic Gastroparesis
Card Set