Rifampicin is a semisynthetic bactericidal antibiotic derived from *Amycolatopsis rifamycinica* (formerly *Streptomyces mediterranei*). It is a cornerstone of first-line anti-tubercular therapy (ATT) in India, used in combination regimens to treat drug-susceptible tuberculosis (TB). It is also a key component of multi-drug therapy (MDT) for leprosy. Its mechanism involves inhibition of DNA-dependent RNA polymerase, leading to suppression of RNA synthesis and bacterial cell death. It is a potent inducer of hepatic cytochrome P450 enzymes, leading to numerous clinically significant drug-drug interactions.
Adult: Tuberculosis: 600mg (or 10mg/kg) once daily, taken on an empty stomach 1 hour before or 2 hours after food. Leprosy: 600mg once monthly (supervised) as part of MDT.
Note: Must be taken on an empty stomach (at least 1 hour before or 2 hours after meals) with a full glass of water. Capsules should be swallowed whole. For patients unable to swallow capsules, contents can be mixed with a small amount of applesauce or jelly. Inform patient about orange-red discoloration of body fluids.
Rifampicin binds with high affinity to the beta-subunit of bacterial DNA-dependent RNA polymerase. This binding forms a stable drug-enzyme complex, thereby inhibiting the initiation step of RNA synthesis. Inhibition of mRNA synthesis leads to a cessation of protein synthesis and ultimately results in bactericidal activity against actively dividing microorganisms.
Pregnancy: Pregnancy Category C (US FDA). Considered generally safe and essential for treating TB in pregnancy. The benefit of treating active TB outweighs potential risk. WHO and NTEP (India) recommend it as part of standard regimen. Neonatal monitoring for bleeding (vitamin K deficiency) may be required.
Driving: Generally safe. May cause dizziness or visual disturbances in rare cases. Patients should be cautious until they know how the drug affects them.
| Isoniazid | Increased risk of hepatotoxicity; monitor LFTs. | Major |
| Oral Contraceptives, Hormonal Replacement Therapy | Decreased efficacy due to enzyme induction; risk of unintended pregnancy. Use non-hormonal backup. | Major |
| Warfarin, Acenocoumarol | Decreased anticoagulant effect; requires frequent INR monitoring and dose adjustment. | Major |
| Antiretroviral Protease Inhibitors (e.g., Atazanavir, Darunavir) & NNRTIs (e.g., Nevirapine) | Significant reduction in ARV levels leading to treatment failure and resistance. Contraindicated or requires adjusted regimens. | Contraindicated/Major |
| Oral Hypoglycemics (Sulfonylureas), Levothyroxine | Decreased therapeutic effect; dose adjustment needed. | Moderate |
| Corticosteroids (e.g., Prednisolone), Theophylline | Increased metabolism, reduced plasma levels and efficacy. | Moderate |
| Ketoconazole, Itraconazole, Fluconazole | Reduced azole levels; may require dose increase. | Moderate |
| Digoxin | Reduced digoxin levels; monitor serum concentrations. | Moderate |
| Beta-blockers (e.g., Propranolol), Calcium Channel Blockers | Decreased effect; may need dose increase. | Moderate |
| Cyclosporine, Tacrolimus | Markedly reduced immunosuppressant levels; risk of graft rejection. Requires close TDM. | Major |
Same composition (Rifampicin (600mg)), different brands: