rifampin (rĭfămˈpĭn) [key], antibiotic used in the treatment of tuberculosis. It is also used to eliminate the meningococcus microorganism from carriers and to treat leprosy, or Hansen's disease. Rifampin, or rifampicin as it was formerly called, acts by inhibiting protein synthesis in sensitive cells. It is a toxic drug whose side effects include flulike symptoms. Because resistant microorganisms emerge during treatment, rifampin is used along with other drugs, e.g., with isoniazid and ethambutol for tuberculosis treatment and with dapsone and clofazimine in the treatment of leprosy.