ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Antibiotic — Rifamycin (Adjunct Only) Pregnancy: Avoid in first trimester; use in second/third trimester only if essential — causes haemorrhagic disease of newborn (give vitamin K at birth)

Rifampicin (Burns — MRSA Adjunct/Biofilm)

Brand names: Rifadin, Rimactane

Adult dose

Dose: 300–600 mg twice daily
Route: Oral / IV
Frequency: Twice daily
Max: 1.2 g/day
NEVER use as monotherapy — rapid resistance development. Used as adjunct to glycopeptides/daptomycin/linezolid for MRSA infections, biofilm-associated infections (prosthetic device infection), and staphylococcal bone/joint infections. Strong enzyme inducer — major drug interactions.

Paediatric dose

Dose: 5–10 mg/kg
Route: Oral
Frequency: Twice daily
Max: 600 mg/dose
5–10 mg/kg twice daily. TB prophylaxis in meningococcal contacts: 10 mg/kg twice daily for 2 days.

Dose adjustments

Renal

No dose adjustment required for mild–moderate impairment.

Hepatic

Reduce dose or avoid in hepatic impairment — hepatotoxic. LFTs mandatory.

Paediatric weight-based calculator

5–10 mg/kg twice daily. TB prophylaxis in meningococcal contacts: 10 mg/kg twice daily for 2 days.

Clinical pearls

  • Warn patients: orange discolouration of urine, sweat, tears, and saliva is expected and harmless — but contact lenses may be permanently stained
  • NEVER monotherapy — resistance develops within days. Always combine with another active agent.
  • Major drug interaction with warfarin — INR may fall dramatically. If both must be used: increase warfarin dose and monitor INR every 2–3 days during and after rifampicin course.

Contraindications

  • Hepatic impairment (significant)
  • Jaundice
  • Concurrent protease inhibitors (antiretrovirals — major interaction)
  • Hypersensitivity to rifamycins

Side effects

  • Orange discolouration of urine, tears, sweat, saliva (harmless — warn patient)
  • Hepatotoxicity
  • Flu-like syndrome (intermittent dosing)
  • Thrombocytopenia
  • Hypersensitivity reactions

Interactions

  • Warfarin (dramatically reduces INR — major interaction; dose needs significant upward adjustment)
  • Oral contraceptives (reduced efficacy — contraception failure)
  • Ciclosporin/tacrolimus (reduced levels — organ rejection risk)
  • Antiretrovirals (complex — specialist advice required)
  • Statins (reduced statin levels)
  • Many other drugs via CYP3A4, CYP2C9 induction

Monitoring

  • LFTs at baseline and monthly
  • FBC (thrombocytopenia)
  • INR if on warfarin
  • Culture sensitivity (confirm in-vitro susceptibility before use)

Reference: BNFc; BNF 90; BSAC Guidelines on Staphylococcal Infection; BNFc; MHRA Drug Safety Update. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators