Rifampin

Rifampin binds strongly to the bacterial DNA-dependent RNA polymerase and thereby inhibits RNA synthesis. It is well absorbed after oral administration and excreted mainly through the liver into bile. Rifampin is distributed widely in body fluids and tissues. It is relatively highly protein- bound, and so adequate cerebrospinal fluid concentrations are achieved only in the presence of meningeal inflammation. Rifampin is used in the treatment of mycobacterial infections.

Rifampin causes a harmless orange color to urine, sweat, and tears. Occasional adverse effects include rashes, thrombocytopenia, nephritis, cholestatic jaundice and occasionally hepatitis. Rifampin induces microsomal enzymes (cytochrome P450), which increases the elimination of anticoagulants, anticonvulsants, and contraceptives. Administration of rifampin with ketoconazole, or chloramphenicol results in significantly lower serum levels of these drugs.