Antituberculous Agents Pregnancy: Use in pregnancy only if the potential benefit justifies the risk to the foetus; given in the last weeks of pregnancy it may cause post-natal haemorrhage in mother and infant (vitamin K1 may be indicated). Excreted in breast milk — avoid breast-feeding unless benefit outweighs risk.

Rifampicin

Brand names: Rifadin, Rimactane

Rifampicin is a first-line rifamycin antibiotic used throughout treatment of active tuberculosis and for some other serious infections and prophylaxis, given orally or intravenously. In respiratory practice it forms a core component of combination TB therapy.

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: Tuberculosis: 8–12 mg/kg as a single daily dose (usual daily dose 450 mg if <50 kg, 600 mg if ≥50 kg)

Route: Oral

Frequency: Once daily

Max: Tuberculosis: usually not exceeding 600 mg daily

Always give with other effective anti-tuberculosis drugs to prevent resistance. Take on an empty stomach, at least 30 minutes before or 2 hours after a meal. Other adult indications: Meningococcal meningitis prophylaxis — 600 mg twice daily for 2 days. Leprosy — 600 mg once monthly (always 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); duration 6 months paucibacillary / 12 months multibacillary. Prophylaxis of Haemophilus influenzae B (adults and children ≥1 month) — 20 mg/kg once daily (max 600 mg/day) for 4 days. Brucellosis, Legionnaires' disease or serious staphylococcal infection — 600–1200 mg/day in 2–4 divided doses with another appropriate antibiotic. Impaired liver function: a daily dose of 8 mg/kg should not be exceeded. US labelling (Rifadin IV) gives the same doses for IV as for oral. Caution in elderly patients (raised blood levels reported), especially with liver impairment.

Paediatric dose

Dose: 15 mg/kg

Route: oral

Frequency: once daily

Max: 600 mg daily

Tuberculosis, children above 3 months: 15 mg/kg (range 10–20 mg/kg) body weight daily; total daily dose should not usually exceed 600 mg. Other paediatric regimens differ by indication — meningococcal prophylaxis: children ≥1 month 10 mg/kg every 12 h for 2 days (children <1 month 5 mg/kg every 12 h; max 600 mg/dose); H. influenzae prophylaxis: children ≥1 month 20 mg/kg once daily (max 600 mg/day) for 4 days (children <1 month 10 mg/kg once daily); leprosy: children >10 years 450 mg once monthly, children <10 years 10–20 mg/kg once monthly. Verify all paediatric dosing against a current children's formulary.

Dose adjustments

Renal

Caution 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

Patient weight (kg)

Verify in a children's formulary

Contraindications

Jaundice
Hypersensitivity to rifampicin or any excipient
Concurrent saquinavir/ritonavir combination
Concurrent lurasidone, sofosbuvir, or the antiretrovirals cabotegravir, fostemsavir or lenacapavir

Side effects

Thrombocytopenia (with or without purpura)
Headache
Dizziness
Nausea
Vomiting

Interactions

Potent inducer of drug-metabolising enzymes (CYP1A2, 2B6, 2C8, 2C9, 2C19, 3A4), UGT and transporters (P-glycoprotein, MRP2) — reduces plasma levels and activity of many co-administered drugs
Severe hepatocellular toxicity with saquinavir/ritonavir (contraindicated)
Increased hepatotoxicity with other hepatotoxic drugs — avoid concomitant halothane; monitor closely when given with isoniazid

Clinical monograph

How it works

It inhibits bacterial DNA-dependent RNA polymerase, suppressing RNA synthesis and exerting a bactericidal effect on susceptible mycobacteria and bacteria.

Prescribing in practice

Rifampicin is a potent inducer of hepatic cytochrome P450 enzymes and reduces the effect of many drugs, including hormonal contraceptives, so review all medicines and advise additional contraception.
It commonly causes orange-red discolouration of urine, tears and other body fluids and can stain soft contact lenses; warn patients this is harmless.
Monitor liver function and use within a multidrug TB regimen to prevent resistance.

Monitoring

Monitor liver function and full blood count, and review for drug interactions and hepatotoxicity throughout treatment.

Counselling the patient

Your urine, tears and sweat may turn orange-red, which is harmless but can stain contact lenses.
Use extra contraception, as rifampicin can stop the pill working.
Take it as prescribed with your other TB medicines and report yellowing of the skin or eyes.

Evidence & guidelines

Established UK tuberculosis guidance positions rifampicin as a core agent throughout combination treatment of active disease.

Reference: NICE NG33 (TB 2016); WHO TB Guidelines 2022; MHRA SPC Rifadin; BTS 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).

Curated clinical cross-links plus same-class fallbacks.

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