Yan Rong1, Patrick Mayo1, Mary H H Ensom2, Tony K L Kiang3. 1. Faculty of Pharmacy and Pharmaceutical Sciences, Katz Group Centre for Pharmacy and Health Research, University of Alberta, Room 3-142D, 11361-87 Ave, Edmonton, AB, T6G 2E1, Canada. 2. Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, Canada. 3. Faculty of Pharmacy and Pharmaceutical Sciences, Katz Group Centre for Pharmacy and Health Research, University of Alberta, Room 3-142D, 11361-87 Ave, Edmonton, AB, T6G 2E1, Canada. tkiang@ualberta.ca.
Abstract
BACKGROUND AND OBJECTIVE: Mycophenolic acid is commonly prescribed to adult kidney transplant recipients. Mycophenolic acid is extensively metabolized to mycophenolic acid-glucuronide (major metabolite) and mycophenolic acid-acyl-glucuronide (minor metabolite). We hypothesized that (1) adult kidney transplant patients on corticosteroid-free regimens exhibit unique mycophenolic acid population pharmacokinetics compared with patients receiving corticosteroid-based therapy, and (2) mycophenolic acid clearance is directly dependent on glucuronide metabolite formation. METHODS: Non-linear mixed-effects modeling was conducted with MonolixSuite-2018R1 (n = 27). Optimal pharmacokinetic models were selected based on objective function values, standard errors, and biological plausibility. RESULTS: Clinical demographic data were sex (female, 16), age (47 ± 13 years, mean ± standard deviation), weight (70 ± 16 kg), height (165 ± 9 cm), albumin (43 ± 4 g/L), serum creatinine (102 ± 27 µmol/L), estimated glomerular filtration rate (61 ± 16 mL/min/1.73 m2), mycophenolic acid dosage (1.4 ± 0.5 g/day, as mycophenolate mofetil), and tacrolimus dosage (5 ± 3 mg/day, immediate release). The population pharmacokinetics of mycophenolic acid can be described by a two-compartment first-order absorption with lag time, and a linear elimination structural model. The apparent oral clearance estimate in the final model (population mean, relative standard error) was 2.87 L/h, 42.3%, which is lower than that reported for similar patients on corticosteroid-based regimens (11.9-26.3 L/h). Other pharmacokinetic parameters were comparable to historical data obtained in corticosteroid-based patients. Both mycophenolic acid-acyl-glucuronide trough concentration and the area under the concentration-time curve ratio were significant covariates that reduced mycophenolic acid apparent oral clearance from 16.5 (base model) to 2.87 L/h. The model was evaluated based on bootstrapping, visual predictive checks, and diagnostic plots. CONCLUSIONS: Our novel findings suggest the potential need to reduce mycophenolic acid dosage in subjects on corticosteroid-free regimens. Corticosteroid-free subjects may also be more sensitive to drug/gene interactions.
BACKGROUND AND OBJECTIVE:Mycophenolic acid is commonly prescribed to adult kidney transplant recipients. Mycophenolic acid is extensively metabolized to mycophenolic acid-glucuronide (major metabolite) and mycophenolic acid-acyl-glucuronide (minor metabolite). We hypothesized that (1) adult kidney transplant patients on corticosteroid-free regimens exhibit unique mycophenolic acid population pharmacokinetics compared with patients receiving corticosteroid-based therapy, and (2) mycophenolic acid clearance is directly dependent on glucuronide metabolite formation. METHODS: Non-linear mixed-effects modeling was conducted with MonolixSuite-2018R1 (n = 27). Optimal pharmacokinetic models were selected based on objective function values, standard errors, and biological plausibility. RESULTS: Clinical demographic data were sex (female, 16), age (47 ± 13 years, mean ± standard deviation), weight (70 ± 16 kg), height (165 ± 9 cm), albumin (43 ± 4 g/L), serum creatinine (102 ± 27 µmol/L), estimated glomerular filtration rate (61 ± 16 mL/min/1.73 m2), mycophenolic acid dosage (1.4 ± 0.5 g/day, as mycophenolate mofetil), and tacrolimus dosage (5 ± 3 mg/day, immediate release). The population pharmacokinetics of mycophenolic acid can be described by a two-compartment first-order absorption with lag time, and a linear elimination structural model. The apparent oral clearance estimate in the final model (population mean, relative standard error) was 2.87 L/h, 42.3%, which is lower than that reported for similar patients on corticosteroid-based regimens (11.9-26.3 L/h). Other pharmacokinetic parameters were comparable to historical data obtained in corticosteroid-based patients. Both mycophenolic acid-acyl-glucuronide trough concentration and the area under the concentration-time curve ratio were significant covariates that reduced mycophenolic acid apparent oral clearance from 16.5 (base model) to 2.87 L/h. The model was evaluated based on bootstrapping, visual predictive checks, and diagnostic plots. CONCLUSIONS: Our novel findings suggest the potential need to reduce mycophenolic acid dosage in subjects on corticosteroid-free regimens. Corticosteroid-free subjects may also be more sensitive to drug/gene interactions.
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