Pharm 101: Rifampicin

Class

Antibiotic

Pharmacodynamics

• Inhibits bacterial RNA synthesis
• Bactericidal for mycobacteria

Pharmacokinetics

• Well absorbed orally
• Highly lipid soluble, widely distributed
• High plasma protein binding
• Hepatic metabolism:
  • Biliary excretion
  • Undergoes enterohepatic recirculation
  • Half-life 3.5 hours
• CYP enzyme inducer

Antimicrobial activity

• Gram positive organisms
• Some gram-negative organisms, including Neisseria, Haemophilus, mycobacteria, and chlamydiae
• Clinical uses:
  • Mycobacterial infections (first line for TB, combination with isoniazid or other antituberculosis drugs)
  • Eliminates meningococcal carriage
  • Prophylaxis following H influenzae exposure
  • Serious Staph infections e.g. endocarditis

Adverse effects

• Orange discolouration of body fluids
• Rash
• Cholestatic jaundice and hepatitis
• Flu-like syndrome with intermittent dosing (if given less than twice per week)
• CYP enzyme inducer

Precautions/contraindications

• Resistance commonly emergences when used as single drug in treatment of active TB
• No dose adjustment required in hepatic or renal insufficiency

References

• Katzung BG. Basic and Clinical Pharmacology. 14e. 2018: 845-846, 851