Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2023 Publisher: Aventis Pharma Limited, 410 Thames Valley Park Drive, Reading, Berkshire, RG6 1PT, UK Trading as: Sanofi, 410 Thames Valley Park Drive, Reading, Berkshire, RG6 1PT, UK
Rifampicin is an active bactericidial antituberculosis drug which is particularly active against the rapidly growing extracellular organisms and also has bactericidial activity intracellularly. Rifampicin has activity against slow and intermittently-growing M. Tuberculosis.
Rifampicin inhibits DNA-dependent RNA polymerase activity in susceptible cells. Specifically, it interacts with bacterial RNA polymerase but does not inhibit the mammalian enzyme. Cross-resistance to rifampicin has only been shown with other rifamycins.
After intravenous administration of a 300 or 600 mg dose of Rifadin infusion infused over 30 minutes to healthy male volunteers (n = 12), mean peak plasma concentrations were 9.0 and 17.5 µg/ml, respectively. The average plasma concentrations in these volunteers remained detectable for 8 and 12 hours, respectively.
The pharmacokinetics (oral and intravenous) in children are similar to adults.
In normal subjects the biological half-life of rifampicin in serum averages about 3 hours after a 600 mg dose and increases to 5.1 hours after a 900 mg dose. With repeated administration, the half-life decreases and reaches average values of approximately 2-3 hours. At a dose of up to 600 mg/day, it does not differ in patients with renal failure and consequently, no dosage adjustment is required.
Rifampicin is rapidly eliminated in the bile and an enterohepatic circulation ensues. During this process, rifampicin undergoes progressive deacetylation, so that nearly all the drug in the bile is in this form in about 6 hours. This metabolite retains essentially complete antibacterial activity. Intestinal reabsorption is reduced by deacetylation and elimination is facilitated. Up to 30% of a dose is excreted in the urine, with about half of this being unchanged drug.
Rifampicin is widely distributed throughout the body. It is present in effective concentrations in many organs and body fluids, including cerebrospinal fluid. Rifampicin is about 80% protein bound. Most of the unbound fraction is not ionized and therefore is diffused freely in tissues.
Not applicable.
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