title: Effects of rifampin on tacrolimus pharmacokinetics in healthy volunteers.
abstract: Tacrolimus is a marketed immunosuppressant used in liver and kidney transplantation. It is subject to extensive metabolism by CYP3A4 and is a substrate for P-glycoprotein-mediated transport. A pharmacokinetic interaction with rifampin, an antituberculosis agent and potent inducer of CYP3A4 and P-glycoprotein, and tacrolimus was evaluated in six healthy male volunteers. Tacrolimus was administered at doses of 0.1 mg/kg orally and 0.025 mg/kg/4 hours intravenously. The pharmacokinetics of tacrolimus were obtained from serial blood samples collected over 96 hours, after single oral and intravenous administration prior to and during an 18-day concomitant rifampin dosing phase. Coadministration of rifampin significantly increased tacrolimus clearance (36.0 +/- 8.1 ml/hr/kg vs. 52.8 +/- 9.6 ml/hr/kg; p = 0.03) and decreased tacrolimus bioavailability (14.4% +/- 5.7% vs. 7.0% +/- 2.7%; p = 0.03). Rifampin appears to induce both intestinal and hepatic metabolism of tacrolimus, most likely through induction of CYP3A and P-glycoprotein in the liver and small bowel.
authors.affiliation: Department of Pharmacy, University of Washington, Seattle 98195-7630, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Hebert
authors.forename: R M
authors.initials: RM
authors.lastname: Fisher
authors.forename: C L
authors.initials: CL
authors.lastname: Marsh
authors.forename: D
authors.initials: D
authors.lastname: Dressler
authors.forename: I
authors.initials: I
authors.lastname: Bekersky
mesh_terms: D000284:Administration, Oral; D000328:Adult; D019540:Area Under Curve; D001682:Biological Availability; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000493:pharmacokinetics*; D007275:Injections, Intravenous; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects; D012293:Rifampin / Q000494:pharmacology*; D016559:Tacrolimus / Q000097:blood / Q000493:pharmacokinetics*