What are the uses for rifampin (Rifampicin)?

Uses for Rifampin (Rifampicin)

Rifampin is primarily indicated for the treatment of tuberculosis (TB), meningococcal carrier state, and as part of regimens for latent tuberculosis infection, with specific dosing considerations required when used with HIV medications due to significant drug interactions.

Primary Uses of Rifampin

1. Tuberculosis Treatment

• First-line agent for drug-susceptible tuberculosis:
  • Part of the standard 6-month regimen consisting of:
    • Intensive phase (first 2 months): Rifampin + Isoniazid + Pyrazinamide + Ethambutol
    • Continuation phase (next 4 months): Rifampin + Isoniazid 1
  • Dosing: Standard dose is 600 mg daily (approximately 10-13 mg/kg) 2
  • Recent evidence supports flat-dosing of rifampin at 600 mg daily as an alternative to weight-based dosing 3

2. Meningococcal Carrier State

• Indicated for eliminating Neisseria meningitidis from the nasopharynx in asymptomatic carriers
• Important: Not indicated for treating meningococcal infection due to risk of rapid resistance development 2
• Should be used only when risk of meningococcal disease is high

3. Latent Tuberculosis Infection (LTBI)

• Used in regimens for LTBI treatment:
  • As monotherapy for 4 months (when pyrazinamide cannot be used)
  • For contacts of isoniazid-resistant, rifampin-susceptible TB: 2-month regimen of rifampin and pyrazinamide 1
  • Note: The 2-month rifampin-pyrazinamide regimen is no longer recommended due to severe liver injury reports 1

4. Tuberculous Meningitis

• Higher doses of rifampin (600 mg IV, ~13 mg/kg) have shown improved survival in tuberculous meningitis compared to standard oral dosing
• Higher doses lead to three times higher plasma concentrations and better cerebrospinal fluid penetration 4

Special Considerations

Drug Interactions

• Potent inducer of cytochrome P450 enzymes (especially CYP3A4) and drug transporters like P-glycoprotein 5
• Significant interactions with:
  • HIV medications (protease inhibitors and NNRTIs)
  • Hormonal contraceptives (reduced effectiveness)
  • Anticoagulants
  • Immunosuppressants
  • Methadone
  • Many other medications 2, 5

HIV Co-infection Considerations

• For HIV patients on antiretroviral therapy:
  • Can be used with NNRTI efavirenz + two NRTIs
  • Can be used with protease inhibitor ritonavir + NRTIs
  • Can be used with ritonavir + saquinavir combination 1
  • Rifabutin may be substituted for rifampin in certain antiretroviral regimens
  • Dose adjustments required when used with certain antiretrovirals 1

Liver Monitoring

• Check liver function before starting treatment
• For patients with normal pre-treatment liver function, routine monitoring is not required
• For patients with chronic liver disease, monitor weekly for two weeks, then every two weeks for the first two months 6
• May cause transient asymptomatic hyperbilirubinemia (0.6% of patients)
• Risk of hepatotoxicity increases when combined with isoniazid 6

Adverse Effects

• Gastrointestinal upset (most common)
• Hepatotoxicity
• Skin eruptions
• Thrombocytopenia (rare)
• Orange discoloration of body fluids (urine, sweat, tears, etc.)
• Potential permanent discoloration of soft contact lenses 1, 2

Contraindications and Cautions

• Use with caution in patients with a history of diabetes mellitus
• Not recommended for intermittent therapy due to risk of renal hypersensitivity reactions
• May affect vitamin D metabolism, potentially reducing serum calcium and phosphate levels
• Patients should be advised not to take other medications without medical advice due to numerous drug interactions 2

Remember that rifampin is a cornerstone of TB treatment, and despite potential toxicities, its benefits in treating active TB generally outweigh the risks when properly monitored and managed.