Rifampicin (also called Rifampin) is an antimycobacterial agent used in the treatment of Tuberculosis. It is a first-line agent used in triple therapy with Isoniazid and Pyrazinamide or quadruple therapy with the addition of Ethambutol.
It acts by inhibiting DNA-dependent RNA polymerase in mycobacteria. At high doses, it can also affect the mammalian equivalent.
The most well known side effect is orange-red discolouration of bodily fluids including urine, faeces, saliva, tears and sweat. Though alarming to patients this is not permanent or harmful.
It is important to note that Rifampicin is a potent liver enzyme inducer and therefore induces its own metabolism and the metabolism of other drugs. Rifampicin is also known to cause Hepatitis.
The derivative Rifabutin causes less hepatic enzyme induction and may be useful in HIV patients to limit breakdown of anti-retrovirals, particularly protease inhibitors.
British National Formulary v.54
Brunton et al. Goodman & Gilman's The Pharmacological Basis of Therapeutics 11th edition.