Rifampisin

Rifampisin, also spelled rifampicin or rifampin, is an antibiotic of the rifamycin class. It is used to treat several mycobacterial infections, particularly active tuberculosis and latent tuberculosis infection, as well as leprosy in combination with other agents, and to prevent meningococcal disease in close contacts of infected patients.

Mechanism of action: Rifampicin binds to the beta subunit of bacterial DNA-dependent RNA polymerase, inhibiting RNA synthesis and thus blocking transcription. This bactericidal activity is mainly against rapidly dividing organisms and is notable for activity against Mycobacterium tuberculosis complex.

Pharmacokinetics: It can be given orally or by injection, with good oral absorption; it is widely distributed and penetrates tissues including the central nervous system when the meninges are inflamed. It is metabolized in the liver and is a potent inducer of hepatic cytochrome P450 enzymes, as well as some drug transporters, leading to many drug interactions. It crosses the placenta and is excreted in breast milk.

Resistance and use in combination: Rifampicin resistance can emerge rapidly when used alone; thus it is always used in combination regimens for tuberculosis and other serious infections. It is a component of standard TB therapy and sometimes used as part of regimens for latent TB. For meningococcal prophylaxis, it is given for a short course to close contacts.

Adverse effects and safety: Common adverse effects include hepatotoxicity, liver enzyme elevations, GI symptoms, rash, and flu-like symptoms. A distinctive harmless side effect is orange-red discoloration of urine, tears, and other secretions. Rarely it causes severe liver injury, hypersensitivity, or serum sickness. It can interact with many drugs, reducing effectiveness of oral contraceptives, anticoagulants, and antiretroviral agents; caution is advised in pregnancy and in hepatic impairment.