1. These antibiotics contain a macrocyclic lactone ring, e.g. erythromycin, azithromycin and clarithromycin.
  1. Functions by inhibition of protein synthesis by binding to the 50S ribosomal RNA
  2. Spectrum of activity is against Gram+ve, Gram-ve and intracellular organisms.
    • Gram+ve: staph, strep, pneumococci and cornebacterium
    • Gram-ve: Neisseria, bordatella, rickettsia and campylobacter
    • Intracellular: Mycoplasma, chlamydia, listeria, legionella and certain mycobacterium.
  3. As such, clinical indications as follows:
    • Respiratory infections
    • Community acquired pneumonia
    • Chlamydial infections
  4. Note that these macrolides may be both bacteriostatic and bactericidal, depending on concentration of drug and organism susceptibility.
  5. Resistance is generally plasmid encoded. Important to remember that cross resistance is complete. The following patterns of resistance are identified:
    • Reduced entry into cell
    • Increased efflux of drug
    • Modification of binding site at ribosome
    • Production of esterases that hydrolyze macrolides.
  1. Metabolised in liver to inactive products.
  2. It is a strong inhibitor of CYP450 enzymes and therefore increases the levels of drugs like warfarin and theophylline.
  1. Mainly in faeces and in bile. Minimal in urine. As such, there is no need for dose adjustment in renal failure.
  1. It is a strong inhibitor of the CYP45- system, and therefore increases levels of drugs such as warfarin, phenytoin and theophylline.
  2. It also increases the serum concentration of digoxin by increasing its oral bioavailability.
Adverse events
  1. GIT side effects are common (remember that erythromycin is used as a prokinetic in the ICU setting) – hence, nausea, vomiting and diarrhea are common.
  2. Acute cholestatic hepatitis (hypersensitivity reaction). Characterized by fever, jaundice and impaired LFTs.
Withdrawal syndrome  
Special notes