Prediction of the effect of voriconazole on the pharmacokinetics of non-steroidal anti-inflammatory drugs.

To evaluate the impact of voriconazole on the pharmacokinetics of Non-steroidal anti-inflammatory drugs (NSAIDs). Pharmacokinetic and physiochemical properties of voriconazole and NSAIDs are applied to build physiologically based pharmacokinetic (PBPK) models using GastroplusTM. The PBPK models of voriconazole and NSAIDs are verified by published studies, respectively. After the successful verification, DDI simulations are applied to predict the effect of voriconazole on the pharmacokinetics of NSAIDs. The area under the plasma concentration-time curves extrapolated to infinity (AUC0-inf) of celecoxib, ibuprofen, tenoxicam and piroxicam are increased by 51%, 7%, 2% and 1% in concurrent use with voriconazole, respectively. The maximum concentration (Cmax) of celecoxib, ibuprofen, tenoxicam and piroxicam are increased by 21%, 1%, 1% and 1% in the presence of concomitant voriconazole, respectively. Considering the inter-patient variability, changes in AUC or Cmax are not clinically meaningful. Therefore, adverse events and toxicity that are associated with celecoxib should be closely monitored when in combination with voriconazole, and this result can provide guidance for clinical DDI studies.

Optimal teicoplanin dosage regimens for methicillin-resistant Staphylococcus aureus infections in endocarditis patients and renal failure patients.

This study aimed to assess whether traditional initial loading and maintenance doses of teicoplanin were appropriate in endocarditis and renal failure patients with methicillin-resistant Staphylococcus aureus (MRSA) infections and to recommend optimal dosage regimens. Pharmacokinetic parameters and physicochemical properties of teicoplanin were performed to develop pharmacokinetic models using GastroPlusTM. Concentration-time curves of teicoplanin in endocarditis and renal failure patients with MRSA infections were simulated by changing clearance (CL) and volume of distribution of the central compartment (Vc). Different teicoplanin dosage regimens were assessed according to the target trough concentration, and optimal teicoplanin dosage regimens were recommended. Dosage regimen of four teicoplanin doses of 6 mg/kg q12 h followed by 6 mg/kg qd is recommended for renal failure patients infected by MRSA. And optimal dosage regimen is five teicoplanin doses of 15 mg/kg q12 h followed by doses of 12 mg/kg qd for endocarditis patients infected by MRSA.

Influence of different proton pump inhibitors on the pharmacokinetics of voriconazole.

This study aimed to determine the influence of proton pump inhibitors (PPIs) on the pharmacokinetics of voriconazole and to characterise potential drug-drug interactions (DDIs) between voriconazole and various PPIs (omeprazole, esomeprazole, lansoprazole and rabeprazole). Using adjusted physicochemical data and the pharmacokinetic (PK) parameters of voriconazole and PPIs, physiologically based pharmacokinetic (PBPK) models were built and were verified in healthy subjects using GastroPlusTM to predict the plasma concentration-time profiles of voriconazole and PPIs. These models were then used to assess potential DDIs for voriconazole when administered with PPIs. The results indicated the PBPK model-simulated plasma concentration-time profiles of both voriconazole and PPIs were consistent with the observed profiles. In addition, the DDI simulations suggested that the PK values of voriconazole increased to various degrees when combined with several PPIs. The area under the plasma concentration-time curve for the time of the simulation (AUC0-t) of voriconazole was increased by 39%, 18%, 12% and 1% when co-administered with omeprazole, esomeprazole, lansoprazole and rabeprazole, respectively. Omeprazole was the most potent CYP2C19 inhibitor tested, whereas rabeprazole had no influence on voriconazole (omeprazole > esomeprazole > lansoprazole > rabeprazole). However, in consideration of the therapeutic concentration range, dosage adjustment of voriconazole is unnecessary regardless of which PPI was co-administered.

Pharmacokinetic/pharmacodynamic analysis of voriconazole against Candida spp. and Aspergillus spp. in children, adolescents and adults by Monte Carlo simulation.

The objective of this study was to investigate the cumulative fraction of response of various voriconazole dosing regimens against six Candida and six Aspergillus spp. in immunocompromised children, immunocompromised adolescents, and adults. Using pharmacokinetic parameters and pharmacodynamic data, 5000-subject Monte Carlo simulations (MCSs) were conducted to evaluate the ability of simulated dosing strategies in terms of fAUC/MIC targets of voriconazole. According to the results of the MCSs, current voriconazole dosage regimens were all effective for children, adolescents and adults against Candida albicans, Candida parapsilosis and Candida orthopsilosis. For adults, dosing regimens of 4 mg/kg intravenous every 12 h (q12h) and 300 mg orally q12h were sufficient to treat fungal infections by six Candida spp. (C. albicans, C. parapsilosis, Candida tropicalis, Candida glabrata, Candida krusei and C. orthopsilosis) and five Aspergillus spp. (Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus, Aspergillus niger and Aspergillus nidulans). However, high doses should be recommended for children and adolescents in order to achieve better clinical efficacy against A. fumigatus and A. nidulans. The current voriconazole dosage regimens were all ineffective against A. niger for children and adolescents. All voriconazole dosage regimens were not optimal against Aspergillus versicolor. This is the first study to evaluate clinical therapy of various voriconazole dosing regimens against Candida and Aspergillus spp. infections in children, adolescents and adults using MCS. The pharmacokinetic/pharmacodynamic-based dosing strategy provided a theoretical rationale for identifying optimal voriconazole dosage regimens in children, adolescents and adults in order to maximise clinical response and minimise the probability of exposure-related toxicity.

Dose regimens for Chinese adult liver transplant recipients according to the genetic polymorphisms of CYP2C9, CYP2C19, and CYP3A5 in recipients and donors.

OBJECTIVE: Genetic polymorphisms of the P450 2C9 enzyme (CYP2C9), CYP2C19 and CYP3A5 gene are known to affect the metabolism of many drugs applied in liver transplant recipients, such as warfarin, voriconazole, and tacrolimus. The aim of this study was to recommend dose regimens for the liver recipients based on CYP2C9, CYP2C19, and CYP3A5 genotypic combinations of liver transplant recipients and their donors. METHODS: 91 adult Han Chinese liver transplant recipients who underwent orthotopic liver transplantation at Tianjin First Central Hospital, China, between 2013 and 2014 were included in this study. CYP2C9*2, CYP2C9*3, CYP2C19* 2, CYP2C19*3 and CYP3A5*3, in both liver recipients and their grafted liver were tested by polymerase chain reaction-restriction fragment length polymorphism. The dose regimens for the liver recipients were recommended based on CYP genotypic combinations of the recipients and their donors. RESULTS: In the liver transplant recipients, the frequencies of CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP2C19*3, and CYP3A5*3 were found to be 2.75%, 4.40%, 0%, 24.18%, and 75.27%, respectively. Allele frequencies were significantly different for CYP2C9*2, CYP2C19*2, and CYP2C19* 3 (p < 0.001) when comparing the recipients with Chinese, Eastern Asians and Caucasians populations. Most dose regimens of drugs, especially of immunosuppressive drugs, should be adjusted according to the variant metabolism activity affected by the genetic polymorphisms in both recipients and their grafted liver. CONCLUSION: The dose regimens would present considerable intraand inter-patient variability in liver transplant recipients since the genetic polymorphisms of P450 enzyme in their grafted liver might complicate the metabolism of drugs in liver transplant recipients. Giving careful consideration to the CYP genotypic combinations of transplant recipients and donors in clinical dose regimens could optimize outcomes.

Assessment of echinocandin regimens by pharmacokinetic/pharmacodynamic analysis against Candida spp. in paediatric patients.

This study aimed to investigate the cumulative fraction of response of various echinocandin (caspofungin, micafungin and anidulafungin) dosing regimens against Candida spp. in paediatric patients with invasive fungal infections (IFIs). Monte Carlo simulations were performed using previously published pharmacokinetic parameters and pharmacodynamic data to evaluate the ability of each echinocandin regimen in terms of fAUC/MIC (free drug area under the concentration-time curve/minimum inhibition concentration ratio) targets of caspofungin, micafungin and anidulafungin. Pharmacodynamic targets were attained in paediatric patients by both caspofungin regimens as well as by a high micafungin dosing regimens against Candida albicans and Candida glabrata. However, the results for anidulafungin suggested that the dosing regimens recommended were not optimal for paediatric patients. In addition, the predicted efficacy of all of the echinocandins against Candida parapsilosis was low. This is the first study to assess caspofungin, micafungin and anidulafungin therapy using Monte Carlo simulation. These results rationalise and optimise the dosage regimens of caspofungin, micafungin and anidulafungin against C. albicans, C. glabrata and C. parapsilosis for paediatric patients with IFIs.

A pharmacokinetic/pharmacodynamic analysis of a standard voriconazole regimen in different CYP2C19 genotypes by Monte Carlo simulation.

OBJECTIVES: The objective of this study was to evaluate the standard voriconazole dosage regimen (maintenance dose was 200 mg bid orally) against Aspergillus infections in different CYP2C19 genotypes from a pharmacokinetic/pharmacodynamic (PK/PD) perspective. METHOD: Monte Carlo simulation (MCS) was applied to simulate 5,000 patients by integrating published pharmacokinetic (PK) parameters, variability of PK parameters on CYP2C19 genotypes and microbiological data. RESULTS: The standard dosage regimen for poor metabolizers (PM) with Aspergillus infections was effective except A. versicolor, for heterozygous extensive metabolizers (HEM), Aspergillus fumigatus, A. terreus and A. nidulans infections could be treated effectively with the standard dosage regimen; for extensive metabolizers (EM), the standard voriconazole dosage regimen failed to achieve the best outcome for the six Aspergillus spp. Increasing dose (e.g. 300 mg bid) or even changing the antifungal drug was needed for EM and most HEM patients with Aspergillus infection. CONCLUSION: Instead of using a standard dosage regimen for all patients, the voriconazole dosage regimen needs to be optimized for patients with different CYP2C19 genotypes.