Macrolides Flashcards
What is the mechanism of action of macrolides?
Macrolides bind to the 50S ribosomal subunit and inhibit bacterial protein synthesis by blocking translocation.
What are the common macrolide antibiotics?
- Erythromycin
- Azithromycin
- Clarithromycin
- Fidaxomicin
Which macrolide has the longest half-life and is commonly used for respiratory infections?
Azithromycin.
Which macrolide is most commonly used for atypical pneumonia?
Azithromycin (effective against Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella).
Which macrolide is used primarily for C. difficile infection?
Fidaxomicin.
Which macrolide is associated with increased GI motility and is sometimes used for gastroparesis?
Erythromycin.
Which macrolides are used for H. pylori eradication?
Clarithromycin (part of triple therapy with amoxicillin and a proton pump inhibitor).
What is the preferred macrolide for treating Mycobacterium avium complex (MAC)?
Azithromycin or Clarithromycin.
What is the preferred treatment for Bordetella pertussis?
Azithromycin or Clarithromycin.
Why should macrolides be used cautiously in patients with heart conditions?
They can cause QT prolongation and increase the risk of Torsades de Pointes.
What are the major side effects of macrolides?
- QT prolongation
- GI distress
- Hepatotoxicity
- Cholestasis (except Clarithromycin, which is renally excreted).
- Eosinophilia
- Inhibition of CYP450 (except azithromycin).
Which macrolide is least likely to inhibit cytochrome P450 enzymes?
Azithromycin.
Which macrolide is known to have the worst drug interactions due to CYP3A4 inhibition?
Erythromycin and Clarithromycin.
What is the primary mode of excretion for macrolides?
Biliary excretion (except Clarithromycin, which is renally excreted).
Why is erythromycin estolate not recommended in pregnancy?
It is associated with hepatotoxicity.
What is a potential macrolide-related toxicity in neonates?
Pyloric stenosis (especially with erythromycin use).
What is the main mechanism of resistance to macrolides?
Methylation of the 23S rRNA binding site prevents macrolide binding to the 50S ribosomal subunit.
