💊 Rifampicin is a cornerstone in TB therapy but a potent enzyme inducer. ⚠️ It reduces oral contraceptive pill (OCP) effectiveness → alternative contraception required. 👁️ Can cause orange-red discolouration of urine, tears, and other secretions (warn patients — contact lenses may stain).

📖 About

Broad-spectrum bactericidal antibiotic.
Key drug in tuberculosis (TB) regimens.
Also used in leprosy, meningococcal carriage eradication, and certain resistant infections.
Check the BNF here for up-to-date prescribing.

⚙️ Mechanism of Action

Binds to the β-subunit of bacterial DNA-dependent RNA polymerase.
Blocks RNA synthesis → bactericidal against mycobacteria.
Potent inducer of hepatic CYP450 enzymes → major source of drug interactions.
Well absorbed, widely distributed.

🎯 Indications

Mycobacterial infections: TB, leprosy.
Meningococcal prophylaxis: eradication of carriage.
Other infections: staphylococcal endocarditis (with other agents), Legionnaire’s disease, brucellosis, some cases of severe CAP.

💊 Dosing – Pyrazinamide (check BNF/local policy)

Indication	Dose & Notes
🌍 Tuberculosis (part of combination therapy)	• Typical adult dose: 10 mg/kg once daily (max 600 mg/day) • Some regimens: 600 mg BD PO/IV (specialist use, severe cases) • Take on an empty stomach before breakfast for best absorption • Check renal and liver function before starting, then monitor regularly

⚠️ Side Effects

Hepatitis: transient ↑ LFTs; rare but serious hepatotoxicity (higher risk with alcohol use or pre-existing liver disease).
Haematological: thrombocytopenia, haemolysis, rare TTP.
Renal: interstitial nephritis, acute renal failure.
Dermatological: Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN).
Secretions: red/orange discolouration of urine, sweat, sputum, tears (harmless but alarming to patients).

⚖️ Cautions

Adjust dose in severe renal/hepatic impairment.
Monitor LFTs, FBC, U&E regularly.
Avoid alcohol (↑ hepatotoxic risk).
Check INR closely if co-prescribed with warfarin.
Warn patients re: contraception failure if using OCP.

⛔ Contraindications

Hypersensitivity to rifamycins.
Acute jaundice or severe hepatic impairment.

🔄 Interactions

Potent CYP450 inducer: ↓ plasma concentration of many drugs.
Reduces efficacy of: – OCP 💊 (contraception failure risk) – Warfarin (↓ INR) – DOAC (↓ effectiveness so check) – Sulphonylureas – Steroids, barbiturates – Calcium channel blockers – Many HIV drugs (notably protease inhibitors & NNRTIs)
Always check BNF for a full list before prescribing.

💡 Clinical Pearls

Always prescribe in combination (never monotherapy in TB — resistance develops rapidly).
Warn patients about orange discolouration of urine, sweat, and tears.
Monitor for hepatitis symptoms: jaundice, abdominal pain, dark urine.
Women on OCP need reliable alternative contraception.

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Rifampicin (Rifabutin Rifampin)