Macrolides

Snapshot

• A 22-year-old woman presents to her gynecologist for a wellness visit. She does not report any acute complaints. She denies any abnormal vaginal discharge, bleeding, lesions, or odors. She is currently sexually active with multiple men and infrequently uses barrier contraception; however, she has an intrauterine device. Pelvic examination is unremarkable.  Laboratory testing is notable for a nucleic acid amplification test that is positive for gonorrhea and chlamydia. She is started on intramuscular ceftriaxone and oral azithromycin.

Introduction

• Mechanism of action
  • impairs bacterial protein synthesis by binding to the 50S ribosomal subunit  
    • inhibits transpeptidation, translocation, and chain elongation
• Medications
  • azithromycin
  • clarithromycin
  • erythromycin
• Mechanism of resistance
  • methylation of the 23 rRNA-binding site 
• Clinical use
  • atypical pneumonia
    • Mycoplasma
    • Chlamydia
    • Legionella
  • sexually transmitted infections (Chlamydia)
  • gram-positive cocci
  • B. pertussis
• Adverse effects
  • gastrointestinal upset
  • QT prolongation 
  • acute cholestatic hepatitis
  • eosinophilia
  • rash
  • P-450 inhibition (clarithromycin and erythromycin)