title: Concomitant clotrimazole therapy more than doubles the relative oral bioavailability of tacrolimus.
abstract: The purpose of this pharmacokinetic study was to determine whether the relative oral bioavailability of tacrolimus is increased with concomitant administration of clotrimazole. Pharmacokinetic studies were conducted in 6 adult kidney transplant patients receiving tacrolimus therapy. Pharmacokinetic profiling was performed by blood sampling over 12 hours before and after the administration of a 5-day course of clotrimazole. Tacrolimus whole-blood concentrations were determined by microparticle enzyme immunoassay. Noncompartmental pharmacokinetic analysis was conducted using WinNonLin, Standard Edition, Version 1.1. Concomitant administration of clotrimazole more than doubled the relative oral bioavailability of tacrolimus. The mean AUC0-12 of tacrolimus was increased 250% with clotrimazole (467.0 +/- 170.0 ng.h/mL versus 188.7 +/- 50.2 ng.h/mL; P = 0.002). Tacrolimus blood trough concentrations also more than doubled with coadministration of clotrimazole (27.7 +/- 10.4 ng/mL versus 11.6 +/- 4.0 ng/mL; P = 0.003). Mean Cmax was significantly increased with clotrimazole (70.7 +/- 34.7 ng/mL versus 27.4 +/- 11.1 ng/mL, P = 0.01). Tmax decreased from 3.2 +/- 1.6 hours to 1.9 +/- 1.0 hours (P = NS). In addition, the apparent oral clearance decreased 60% with coadministration of clotrimazole (median oral clearance 0.16 L/h/kg versus 0.40 L/h/kg; P = 0.03). Thus, clotrimazole causes a significant increase in the relative oral bioavailability, Tmax, and trough concentration of tacrolimus. Tacrolimus levels should be monitored following initiation or discontinuation of clotrimazole to minimize toxicity or precipitation of an acute rejection episode due to subtherapeutic levels.
authors.affiliation: University of Illinois at Chicago, College of Pharmacy, Department of Pharmacy Practice, Chicago, Illinois 60612, USA. evasquez@uic.edu
authors.forename: Eva M
authors.initials: EM
authors.lastname: Vasquez
authors.forename: Grace P
authors.initials: GP
authors.lastname: Shin
authors.forename: Nicole
authors.initials: N
authors.lastname: Sifontis
authors.forename: Enrico
authors.initials: E
authors.lastname: Benedetti
mesh_terms: D000328:Adult; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D019540:Area Under Curve; D001682:Biological Availability; D003022:Clotrimazole / Q000494:pharmacology*; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology; D004347:Drug Interactions; D016903:Drug Monitoring; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000493:pharmacokinetics*; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D016559:Tacrolimus / Q000493:pharmacokinetics*
chemical_list: D000891:Anti-Infective Agents, Local; D065607:Cytochrome P-450 Enzyme Inhibitors; D007166:Immunosuppressive Agents; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; D003022:Clotrimazole; D016559:Tacrolimus