Elongation is not inhibited. Rifampin binds to the beta-subunit of the holoenzyme. Higher concentrations are required to inhibit mammalian mitochondrial RNA synthesis. Pharmacokinetics Rifampin is well absorbed after PO administration, usually q1d. The half-life of rifampin is 1.5 to 5 h and is increased by hepatic dysfunction.
Rifampin is deacetylated to a form that is still active as an antibacterial.
Rifampin and its deacetylated form are eliminated in the bile, but the deacetylated form is less bioavailable so, despite the enterohepatic circulation , rifampin is eventually eliminated. Elimination is slowed by hepatic dysfunction and slow acetylators taking isoniazid. Hepatic microsomes which deacetylate the drug are induced. Jaundice Most notable problem and has resulted in death. Hepatitis is rare in patients with normal liver function, but chronic liver disease, alcoholism, and old age appear to increase the incidence.