An Assessment of Voriconazole Pharmacokinetics and Pharmacogenetics in Liver Transplant Recipients - Pilot Study

A fixed-dosing regimen of voriconazole is routinely used as prophylaxis against aspergillosis in liver transplant patients admitted to the transplant intensive care unit at UPMC. We hypothesize that use of a fixed-dosing regimen of voriconazole will lead to a large degree of variability in drug exposure among liver transplant patients due to: 1) variability in absorption and elimination caused by physiological characteristics unique to this patient population 2) its non-linear pharmacokinetics and 3) the potential for polymorphism in the genes that encode for cytochrome P-450 enzymes that metabolize voriconazole. This is a pilot clinical pharmacokinetic evaluation that will: 1) characterize the plasma concentration versus time profile of voriconazole in liver transplant patients receiving a fixed-dosing regimen to assess for extremes in systemic exposure 2) determine the oral bioavailability of voriconazole in liver transplant patients 3) assess for functionally significant allelic variation of the cytochrome P-450 enzymes that metabolize voriconazole (CYP2C9, CYP2C19 and CYP3A4/5) in both recipient blood and allograft tissue that may contribute extremes in systemic exposure among liver transplant patients. This evaluation will allow for an assessment of the adequacy of the prophylactic regimen in achieving therapeutic drug concentrations in all subjects. Additionally, the utility of genotyping as a clinical tool to identify patients at risk for extremes in voriconazole exposure will be evaluated. The characterization of the pharmacokinetics in liver transplant patients may be utilized to define an optimal therapeutic regimen that will be individualized to target specific concentrations to maximize efficacy and minimize side-effects.