Rifampicin (Rifabutin Rifampin) 💊

💊 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)

⚠️ 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.