Rifampin is the most commonly used oral/IV antibiotic among the rifamycins (rifabutin, rifapentine, etc.) Rifampin acts at the level of RNA transcription by inhibiting bacterial DNA-dependent RNA polymerase. This drug has excellent oral bioavailability and tends to concentrate intracellularly. Classically, rifampin is used in combination with the medications like isoniazid to treat latent and active tuberculosis, but it also has in vitro activity against pneumococcus, group A strep, viridans strep, CONS, and a myriad of gram negative organisms.
Although renal dose adjustments aren’t typically required, hepatotoxicity is a real concern with rifampin (especially when used with other medications), so labs and symptoms (upset stomach, abdominal pain, nausea, etc.) should clue one in! Rifampin also induces cytochrome P450 (specifically the CYP3A locus) thereby accelerating the metabolism of many drugs. Be sure to review a patient’s medications to see which might be affected by starting rifampin.
Oh, and it stains body fluids orange. Kind of cool! 🙂
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