21. Macrolides - What does"Complications Mean Macrolides...

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Macrolides, Clindamcyin and Tetracycline What does “Complications” Mean? Staph aureus (MRSA) Strep pneumoniae Enterococcus faecalis (VRE or GRE) All are Gram Positives! Macrolides • Azithromycin • Clarithromycin • Erythromycin • Dirithromycin Macrolides • Mechanism of action: – inhibit bacterial RNA dependent protein synthesis – bind irreversibly to the 50S subunit of BACTERIAL ribosomes – binding site is close to that of clindamycin and chloramphenicol (may interfere with action) – concentrate in macrophages and PMN Macrolides • Mechanisms of resistance: – alteration of binding site in the ribosome (non- plasmid) – degradation of antibiotic by bacterial enzymes (plasmid encoded erythromycin esterase) – active efflux (pumping out) of antibiotic – bacterial membrane changes lead to inability of antibiotic to enter bacteria Macrolides • Pharmokinetics: Acid stable Half life (hr) Food? Well absorbed? Erythromycin No 2 interferes yes Clarithromycin Yes 4 increases yes Azithromycin Yes 40 interferes yes
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Macrolides • Useage: – gram positives: Clarithro >Erythro > Azithro ( S. aureus, Streptococci , no good for MRSA) – Gram negatives: Azithro> Clarithro > Erythro ( H. influenza , M. catarrhalis , entric gram negatives) –STD’s : • Clarith>Erythro>Azithro ( C. trachomatis ) • Azithro>> erythro=clarithro ( N. gonorrhoeae ) Macrolides • Adverse effects: – Epigastric distress (diarrhea, abdominal pain, nausea) frequently leads to non-compliance (erythro most common)
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21. Macrolides - What does"Complications Mean Macrolides...

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