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Rifamycin Antibiotic Pregnancy: Use in pregnancy or in women of childbearing potential only if the potential benefit justifies the potential risk to the foetus; teratogenic at very high doses in animals and crosses the placenta. Administration in the last few weeks of pregnancy may cause post-natal haemorrhage in mother and infant (vitamin K1 may be indicated). Breast-feeding: excreted in breast milk; infants should not be breast-fed unless the benefit to the patient outweighs the risk to the infant (UK SPC §4.6).

Rifampicin

Brand names: Rimactane, Rifadin

Rifampicin is an antibiotic central to tuberculosis treatment and used for some other serious infections (e.g. as part of combination therapy in prosthetic-related or staphylococcal infection) and for meningococcal prophylaxis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 450 mg (<50 kg) or 600 mg (>=50 kg); single daily dose 8-12 mg/kg
Route: Oral
Frequency: Once daily
Tuberculosis, adults: recommended single daily dose 8-12 mg/kg — usual daily dose 450 mg if <50 kg, 600 mg if >=50 kg. Must be given with other effective anti-tuberculosis drugs to prevent emergence of resistance. Prophylaxis of meningococcal meningitis, adults: 600 mg twice daily for 2 days. Leprosy, adults: 600 mg once per month with at least one other anti-leprosy drug; if a daily regimen is indicated, 10 mg/kg (usual 450 mg if <50 kg, 600 mg if >=50 kg). Prophylaxis of Haemophilus influenzae B, adults and children >=1 month: 20 mg/kg once daily (maximum 600 mg/day) for 4 days. Brucellosis, Legionnaires' disease or serious staphylococcal infections, adults: 600 mg to 1200 mg daily in 2-4 divided doses with another appropriate antibiotic. Impaired liver function: a daily dose of 8 mg/kg should not be exceeded. Take on an empty stomach, at least 30 minutes before or 2 hours after a meal, to ensure rapid and complete absorption.

Paediatric dose

Dose: 15 mg/kg
Route: Oral
Frequency: Once daily
Max: 600 mg daily
Tuberculosis, children above 3 months: 15 (range 10-20) mg/kg body weight daily, total daily dose not usually exceeding 600 mg. Meningococcal meningitis prophylaxis: children >=1 month 10 mg/kg every 12 hours for 2 days; children <1 month 5 mg/kg every 12 hours for 2 days (dose must not exceed 600 mg/dose). Leprosy: children >10 years 450 mg once a month; children <10 years 10-20 mg/kg once a month. H. influenzae B prophylaxis: children >=1 month 20 mg/kg once daily (maximum 600 mg/day) for 4 days; children <1 month 10 mg/kg once daily for 4 days.

Dose adjustments

Renal

Caution should be taken in renal impairment if the dose exceeds 600 mg/day (§4.4).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Tuberculosis, children above 3 months: 15 (range 10-20) mg/kg body weight daily, total daily dose not usually exceeding 600 mg. Meningococcal meningitis prophylaxis: children >=1 month 10 mg/kg every 12 hours for 2 days; children <1 month 5 mg/kg every 12 hours for 2 days (dose must not exceed 600 mg/dose). Leprosy: children >10 years 450 mg once a month; children <10 years 10-20 mg/kg once a month. H. influenzae B prophylaxis: children >=1 month 20 mg/kg once daily (maximum 600 mg/day) for 4 days; children <1 month 10 mg/kg once daily for 4 days.

Verify in a children's formulary

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION Rifampin can be administered by the oral route or by IV infusion (see INDICATIONS AND USAGE ). IV doses are the same as those for oral. See CLINICAL PHARMACOLOGY for dosing information in patients with renal failure. Tuberculosis Adults: 10 mg/kg, in a single daily administration, not to exceed 600 mg/day, oral or IV Pediatric Patients: 10–20 mg/kg, not to exceed 600 mg/day, oral or IV It is recommended that oral rifampin be administered once daily, either 1 hour before or 2 hours after a meal with a full glass of water. Rifampin is indicated in the treatment of all forms of tuberculosis. A three-drug regimen consisting of rifampin, isoniazid, and pyrazinamide is …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2026-05-27. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

  • Presence of jaundice
  • Hypersensitivity to rifampicin or to any of the excipients
  • Concurrent administration with the combination of saquinavir/ritonavir
  • Concurrent use with medicines strongly affected by rifampicin's enzyme/transporter induction, such as lurasidone, sofosbuvir, and the antiretrovirals cabotegravir, fostemsavir and lenacapavir

Side effects

  • Thrombocytopenia with or without purpura (common, usually with intermittent therapy; reversible if drug stopped when purpura occurs)
  • Nausea, vomiting (common); diarrhoea (uncommon)
  • Headache, dizziness (common)
  • Drug-induced liver injury (including fatal cases, especially in combination with other anti-TB drugs), hepatitis, hyperbilirubinaemia
  • Severe cutaneous reactions — erythema multiforme including Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS, AGEP; discoloration of body fluids (tears, sweat, sputum) and teeth

Interactions

  • Potent inducer of drug-metabolising enzymes and transporters — reduces plasma concentrations and efficacy of many co-administered drugs; contraindicated with saquinavir/ritonavir and with lurasidone, sofosbuvir, cabotegravir, fostemsavir and lenacapavir (§4.3)
  • Concurrent isoniazid: caution regarding hepatotoxicity, particularly in impaired liver function, the elderly, malnourished patients and possibly children under two years (§4.4)

Clinical monograph

How it works

It inhibits bacterial DNA-dependent RNA polymerase, blocking transcription.

Prescribing in practice

  • It is a potent enzyme inducer with many interactions — it reduces the effectiveness of hormonal contraception, warfarin, many antiretrovirals and others; counsel and adjust accordingly.
  • It must be used in combination (never alone) for active TB to prevent resistance; hepatotoxicity occurs (monitor).
  • It colours urine, tears, sweat and other secretions orange-red (harmless, but stains soft contact lenses); intermittent dosing can cause a flu-like reaction.

Monitoring

Monitor liver function (and full blood count); review all co-medications for interactions.

Counselling the patient

  • Your urine, tears and sweat may turn orange-red — this is harmless but can stain contact lenses.
  • It makes the contraceptive pill and some other medicines less effective — use additional contraception and tell your clinician about all your medicines.
  • Report yellowing of the skin or eyes, or feeling unwell.

Evidence & guidelines

A cornerstone of TB therapy (always in combination) and used for selected other infections and prophylaxis (NICE NG33).

Reference: NICE NG33 TB; British Thoracic Society TB Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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