Pharm 101: Chloramphenicol

Class

Antibiotic

Pharmacodynamics

• Bacteriostatic
• Inhibits protein synthesis:
  • Binds reversibly to 50S subunit of the bacterial ribosome
  • Inhibits peptide bone formation

Pharmacokinetics

• IV administration of prodrug
• Widely distributed to all tissues
  • CNS/CSF concentrations equal to serum
• Metabolism to inactive metabolites by:
  • Conjugation with glucuronic acid (hepatic)
  • Reduction to inactive aryl amines
• Renal excretion of active (10%) and inactive drug

Antimicrobial activity

• Broad spectrum antibiotic active against both gram-positive and gram-negative organisms
  • H influenza, Neisseria are highly susceptible
• Also active against rickettsiae
• Does not treat chlamydiae
• Clinical uses:
  • Rarely used
  • Rickettsial infections
  • Bacterial meningitis if penicillin allergic

Adverse effects

• GI upset
• Bone marrow suppression
  • Dose-related reversible suppression of RBC production
• Gray baby syndrome (flaccidity and shock) in newborn infants
  • Lack effective glucuronic acid conjugation mechanism
  • Require dose reduction
• CYP enzyme inhibitor
  • Half-life of phenytoin and warfarin prolonged

Precautions/contraindications

• Caution in hepatic and renal insufficiency
• Dose reduction in newborns and premature infants

References

• Katzung BG. Basic and Clinical Pharmacology. 14e. 2018: 822-824