Utility of cystatin C and serum creatinine-based glomerular filtration rate equations in predicting vancomycin clearance: A population pharmacokinetics analysis in elderly Chinese patients.

Renal function is an important factor affecting the pharmacokinetics of vancomycin. The renal function in elderly patients gradually decreases with age. An accurate estimated glomerular filtration rate (GFR) is essential in drug dosing. The study aimed to determine the most appropriate renal function estimation equations to describe vancomycin pharmacokinetics in elderly patients using population pharmacokinetic analysis. Data were obtained retrospectively from elderly patients aged ≥65 years who received vancomycin for infection from September 2016 to January 2022. Renal function was estimated using the Cockcroft-Gault equation (CG), Modification of Diet in Renal Disease equation (MDRD), three Chronic Kidney Disease Epidemiology Collaboration equations (CKD-EPIcys-scr , CKD-EPIscr , and CKD-EPIcys ) and two Berlin Initiative Study equations (BIS-1 and BIS-2). The CKD-EPIcys-scr and BIS-2 equations were based on cystatin C (Cys C) and serum creatinine (Scr). The others were based on Cys C or Scr. A nonlinear mixed effects model (NONMEM) was used to develop the population pharmacokinetic model. A total of 471 serum concentrations from 313 elderly patients were used to develop the population pharmacokinetic model. Weight and GFR were identified as significant covariates affecting the pharmacokinetics of vancomycin. Cys C and Scr-based GFR (CKD-EPIcys-scr and BIS-2) yielded significant improvement performance compared with the other equations in model building. The interindividual variability of CL was reduced from 49.4% to 23.6% and 49.4% to 23.7% in CKD-EPIcys-scr and BIS-2 based models, respectively. However, greater interindividual variabilities of CL (from 26.6% to 29.0%) were represented in the other five models which were based on either Cys C or Scr. The GFR estimated by EPIcys-scr and BIS-2 equations and vancomycin CL exhibited a good correlation (r = 0.834 and 0.833). In the external validation with 124 serum concentrations, the predictive performances of the CKD-EPIcys-scr and BIS-2 based models (the mean relative prediction errors were less than 1%, the mean relative absolute prediction errors were about 23%) were also superior to the other five models (the mean relative prediction errors were about 2%, the mean relative absolute prediction errors were greater than 25%) which are based on either Cys C or Scr. In this study, we determined that the equation used to estimate GFR can affect the population pharmacokinetic model fitting result. Population pharmacokinetics model with CKD-EPIcys-scr or BIS-2 can be used to optimize vancomycin dosage in elderly Chinese patients.

Determination of valproic acid and its six metabolites in human serum using LC-MS/MS and application to interaction with carbapenems in epileptic patients.

Valproic acid (VPA) is a classic medication for several types of epilepsy and mood disorders, and some of its effectiveness and toxicity is associated with metabolites. Although many reports have reported the drug-drug interactions of VPA, no study has focused on the influence of carbapenems (CBPMs) on VPA's active metabolites. An LC-MS/MS method for determining VPA and its six metabolites (3-hydroxy valproic acid, 4-hydroxy valproic acid, 2-propyl-2-pentenoic acid, 2-propyl-4-pentenoic acid, 3-keto valproic acid, and 2-propylglutaric acid) in human serum was established and applied to evaluate the drug-drug interaction with CBPMs in epileptic patients. The stable isotope valproic acid-d6 was used as an internal standard. Analytes in serum samples (50 µl) were isolated using a Kinetex C18 column (3 × 100 mm, 2.6 µm) and detected via negative electrospray ionization after protein precipitation. It was linear (r > 0.99) over the calibration range for different analytes. The accuracy was 91.44-110.92%, and the precision was less than 9.98%. The matrix effect, recovery, and stability met the acceptance criteria. According to the data collected from 150 epileptic patients, the concentration-dose ratio for VPA and its metabolites decreased with CBPM polytherapy. This method is simple and rapid with great accuracy and precision. It is suitable for routine clinical analysis of VPA and its metabolites in human serum.

Population pharmacokinetics of ciclosporin in allogeneic hematopoietic stem cell transplant recipients: C-reactive protein as a novel covariate for clearance.

WHAT IS KNOWN AND OBJECTIVES: Ciclosporin (CsA), a potent immunosuppressive agent used to prevent graft-versus-host disease in allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients, is characterized by large inter-individual variability and a narrow therapeutic range. The aim of this study was to develop a population pharmacokinetic model for CsA in Chinese allo-HSCT recipients and to identify covariates influencing CsA pharmacokinetics. METHODS: A total of 758 retrospective drug monitoring data points were collected after intravenous infusion or oral administration of CsA from 59 patients. Population pharmacokinetic analysis was performed using nonlinear mixed effects modelling expressed by differential equations. Monte Carlo simulation was applied to optimize dosage regimens. The final model was validated using bootstrap and normalized prediction distribution errors. RESULTS AND DISCUSSION: The results showed that the daily CsA dose, haematocrit, total bile acid, C-reactive protein (CRP) and co-administration of triazole antifungal agent were identified as significant covariates for clearance (CL) of CsA. The typical value of CL was 19.8 L/h with an inter-individual variability of 13.1%. The volume of distribution was 1340 L. Bioavailability was 67.2% with an inter-individual variability of 8.5%. Dosing simulation based on the developed model indicated that patients with high CRP concentration required a higher daily dose to attain the therapeutic trough concentration. The influence of CRP ultimately on the therapy outcome of CsA is not clear, which needs further study. WHAT IS NEW AND CONCLUSION: CRP concentration was identified as a novel marker associated with CsA pharmacokinetics, which should be considered when determining the appropriate dosage of CsA in allo-HSCT recipients.

P-glycoprotein associated with diabetes mellitus and survival of patients with pancreatic cancer: 8-year follow-up.

Diabetes mellitus (DM) has a high prevalence in patients with pancreatic cancer (PaC), but the prognostic value of DM in PaC remains controversial. Alterations of P-glycoprotein (P-gp) and cytochrome P450 3A4 (CYP3A4) contribute to multidrug resistance and intestinal metabolism in a variety of cancer types, which may be implicated in DM development. This study aimed to explore the potential prognostic value of P-gp and CYP3A4 in PaC patients in the context of DM through long-term follow-up. We retrospectively reviewed the medical records of patients with PaC admitted at The First People's Hospital of Changzhou, Jiangsu, China, from January 2011 to November 2019 and identified two cohorts of adult patients with PaC, including 24 with DM and 24 without DM (non-DM). The baseline clinical characteristics and outcomes were compared. Immunohistochemistry showed that protein expression of P-gp, but not CYP3A, in duodenum tissues was significantly upregulated in PaC patients with DM compared with those without DM. Kaplan-Meier analysis and log-rank test showed that the survival of patients with PaC and DM/high expression of P-gp was not significantly reduced compared with that of patients without DM/low expression of P-gp. These findings suggested that P-gp expression levels were different in the DM and non-DM groups of patients with PaC, but DM and duodenal P-gp levels were not associated with the long-term survival of patients with PaC. It appears that the presence of DM or P-gp expression levels may not serve as effective prognostic markers for PaC.

Pharmacokinetics of omeprazole in rats with dextran sulfate sodium-induced ulcerative colitis.

Omeprazole is a commonly used drug in patients with ulcerative colitis (UC). This study investigated the pharmacokinetics of omeprazole in rats with UC induced by dextran sulfate sodium (DSS). The pharmacokinetics of intravenously administered omeprazole (20 mg/kg) was investigated in normal and UC rats using LC-MS/MS. The formation of 5-OH omeprazole, a main metabolite of omeprazole, in rat liver microsomes (RLMs) from normal and UC rats was compared. The protein levels of CYP1A2, CYP2D1, and CYP3A1 in the liver were measured by Western blot. Compared with normal rats, UC rats had increased plasma concentrations of omeprazole, resulting in an increased AUC0-240 min and decreased CL. DSS treatment decreased the formation rate of 5-OH omeprazole in RLMs but did not change the affinity of the enzymes. The Vmax and CLint of RLMs from UC rats were 62% and 48% those of RLMs from normal rats, respectively. The hepatic CYP1A2 and CYP3A1 protein levels in UC rats were 42.6 and 45.2% lower than those in normal rats, respectively; however, the protein levels of CYP2D1 in the two groups were similar. The activity and expression of some hepatic CYP450 isoforms were decreased by UC, leading to changes in the pharmacokinetics of omeprazole.

Effects of CYP3A5, ABCB1 and POR*28 polymorphisms on pharmacokinetics of tacrolimus in the early period after renal transplantation.

1. We aimed to establish a population pharmacokinetic (PK) model of tacrolimus and identify clinical covariates, especially the genetic polymorphisms of CYP3A5, ABCB1 and POR*28 that affected the PK to prevent fluctuation in the trough concentration of tacrolimus during the early period after renal transplantation. 2. Tacrolimus trough concentration, clinical data and CYP3A5/ABCB1/POR28 genotypes were retrospectively collected from 234 kidney transplant recipients during the first month post-transplantation. The population PK model was built using the non-linear mixed effects modeling software NONMEM. Dosing simulation was performed based on the final model. 3. A one-compartment model with first-order absorption and elimination was used to characterize the PK of tacrolimus. Among the genotypes, only CYP3A5 genotype was confirmed to have clinical significance. The final model describing CL/F (l/h) was as follows: 23.3 × ( HCT / 0.309 ) - 0.445   × [ ( 0.897 ,   i f   POD   > 10 ) o r   ( 1 , i f   POD   ≤ 10 ) ] × ( 0.657 , i f   CYP 3 A 5 * 3 / * 3   genotype ) . The inter-individual variability in CL/F was 21.9%. Monte Carlo simulation based on the final model was carried out to determine the optimal dosage regimen. 4. CYP3A5 genotype, post-operative day and hematocrit were confirmed as critical PK factors of tacrolimus. The model could be used to accurately predict individual PK parameters of tacrolimus and provide valuable insights into the dosage optimization.

P-glycoprotein associated with diabetes mellitus and survival of patients with pancreatic cancer: 8-year follow-up

Diabetes mellitus (DM) has a high prevalence in patients with pancreatic cancer (PaC), but the prognostic value of DM in PaC remains controversial. Alterations of P-glycoprotein (P-gp) and cytochrome P450 3A4 (CYP3A4) contribute to multidrug resistance and intestinal metabolism in a variety of cancer types, which may be implicated in DM development. This study aimed to explore the potential prognostic value of P-gp and CYP3A4 in PaC patients in the context of DM through long-term follow-up. We retrospectively reviewed the medical records of patients with PaC admitted at The First People's Hospital of Changzhou, Jiangsu, China, from January 2011 to November 2019 and identified two cohorts of adult patients with PaC, including 24 with DM and 24 without DM (non-DM). The baseline clinical characteristics and outcomes were compared. Immunohistochemistry showed that protein expression of P-gp, but not CYP3A, in duodenum tissues was significantly upregulated in PaC patients with DM compared with those without DM. Kaplan-Meier analysis and log-rank test showed that the survival of patients with PaC and DM/high expression of P-gp was not significantly reduced compared with that of patients without DM/low expression of P-gp. These findings suggested that P-gp expression levels were different in the DM and non-DM groups of patients with PaC, but DM and duodenal P-gp levels were not associated with the long-term survival of patients with PaC. It appears that the presence of DM or P-gp expression levels may not serve as effective prognostic markers for PaC.

Population Pharmacokinetics and Pharmacodynamics of Piperacillin/Tazobactam in Patients with Nosocomial Infections.

OBJECTIVE: The study was to establish a population pharmacokinetic (PPK) model of piperacillin (PIP) and tazobactam (TAZ) that explain pharmacokinetic variability and to propose optimized dosage regimens in patients with nosocomial infections. METHODS: In total, 310 PIP and 280 TAZ concentration-time points were collected at steady state over multiple dosing intervals from 50 patients who received PIP/TAZ infused within 30 min or over 3 h. Drug analysis was performed by high-performance liquid chromatography (HPLC). Nonlinear mixed effects modeling was employed to develop PPK model and 1000 Monte Carlo simulation was used to predict the probability of target attainment (PTA) with a target time of non-protein-bound concentration above MIC > 50 % of the dosing interval. RESULTS: A model with one-compartment model had the best predictive performance for the PPK model. The population estimates of PIP were 13.8 L/h (31.1 %) for clearance (CL) and 21.7 L (38 %) for volume of distribution (V). The population estimates of TAZ were 9.3 L/h (29.1 %) for CL and 16 L (35.3 %) for V. Influence of creatinine clearance (CLcr) and body weight were identified as important covariates for PIP/TAZ CL and V, respectively. A 30-min infusion of 4 g every 6 h achieved robust (≥90 %) PTAs for MIC ≤ 16 mg/L. As an alternative mode of administration, a 3-h infusion of 4 g every 6 h achieved robust PTAs for Pseudomonas aeruginosa and Klebsiella pneumoniae. CONCLUSIONS: Prolonged infusions achieved better PTAs compared with shorter infusions at similar daily doses. This benefit was most pronounced for MICs between 16 and 40 mg/L.

Cisplatin-based chronotherapy for advanced non-small cell lung cancer patients: a randomized controlled study and its pharmacokinetics analysis.

PURPOSE: We intended to evaluate the superiority of cisplatin-based chronotherapy in the treatment of patients with advanced non-small cell lung cancer (NSCLC) and investigate the relationship between the circadian rhythm and the variability of pharmacokinetics for cisplatin. METHODS: Forty-one patients with advanced NSCLC were divided into two groups with minimization randomization, including routine group (24 cases) and chronotherapy group (17 cases). The clinical effect and toxicity between the two groups were investigated. The population pharmacokinetics of cisplatin was calculated using nonlinear mixed-effects modeling method. RESULTS: There is no significant difference in total response rate between chronotherapy group (52.94%) and routine chemotherapy group (50.00%), p = 0.853. The rate of leucopenia (grade 3 or 4) in chronotherapy group (11.76%) is significantly lower than that in routine chemotherapy (37.50%), p < 0.05. The rate of neutropenia (grade 3 or 4) in chronotherapy group (11.76%) is significantly lower than that in routine chemotherapy group (33.33%), p < 0.05. The proportion of gastrointestinal toxicity (nausea, grade 1 vs 2) in chronotherapy group is significantly lower than that in routine chemotherapy, p < 0.05. When cisplatin was administered at 18:00, the CL was 1.38- and 1.22-fold higher than those administered at 6:00 for total and unbound cisplatin, respectively (p < 0.05). CONCLUSIONS: Cisplatin-based chronotherapy has advantage in relieving side effects of chemotherapy, and circadian could influence the metabolism of cisplatin, and more clinical researches are needed.

Circadian variability of pharmacokinetics of cisplatin in patients with non-small-cell lung carcinoma: analysis with the NONMEM program.

PURPOSE: The aim of this study was to describe the nonlinear pharmacokinetics of total and unbound plasma cisplatin under different administered time in patients with non-small-cell lung carcinoma. METHODS: Patients receiving chemotherapy with cisplatin were included in this analysis. Patients were divided into two groups depending on the administrated time of cisplatin: 6:00 (Group A) and 18:00 (Group B). The population pharmacokinetics of cisplatin was calculated using nonlinear mixed-effects modeling (NONMEM) method, and the possible influence of covariates on the population pharmacokinetics of cisplatin was also explored. RESULTS: The pharmacokinetics of total and unbound cisplatin could be described well by a linear two-compartment model. The mean population estimates for total and unbound drug were, respectively, 0.463 (17.0 %) and 25.4 (14.0 %) l h⁻¹ for clearance (CL), 24.2 (19.9 %) and 20.5 (27.1 %) l for central distribution volume (V1), 10.2 (18.2 %) and 9.82 (28.1) l h⁻¹ for intercompartmental clearance (Q) and 32.0 (24.1 %) and 6.77 (25.4 %) l for peripheral compartment volume (V2). The CL for total and unbound cisplatin was dependent on body surface area (BSA). When cisplatin was administered at 18:00, the CL was 1.38- and 1.22-fold higher than those administered at 6:00 for total and unbound cisplatin, respectively (P < 0.05). The mean parameter estimates from a nonparametric bootstrap procedure were comparable and within 5 % of the estimates from NONMEM. CONCLUSIONS: The results showed that circadian could influence the metabolism of cisplatin and suggested the conventional dose adjustment of cisplatin based on BSA.

Desensitization of allergy to human insulin and its analogs by administering insulin aspart and insulin glargine.

Insulin allergy is a rare clinical situation. We report a 51-year-old patient with type 2 diabetes who required multiple daily insulin injections. The patient developed allergy to human regular insulin and insulin analogs (insulin aspart and insulin glargine), which was resolved by subcutaneous insulin desensitization.

Population pharmacokinetics of digoxin in elderly patients.

This study was aimed at determining the population pharmacokinetics of digoxin and identifying factors that explain pharmacokinetic variability in elderly patients. The data of 142 elderly patients and 448 samples were collected after repetitive oral digoxin. Blood samples were drawn at various times after administration. Population pharmacokinetic analysis was performed using nonlinear mixed effects modelling program (NONMEM). A one-compartment model with first-order absorption and elimination was selected as the base model. The influence of demographic characteristics, biochemical and haematological indices as well as other commonly used co-medications were explored. The typical values with interindividual variability for apparent clearance (CL/F) and apparent volume of distribution (V/F) were 8.9 L h(-1) (43.2 %) and 420 L (65.8 %), respectively. The residual variability was 31.6 %. CL/F decreased significantly with renal function, total body weight, calcium channel blockers or spironolactone co-therapy and symptom with congestive heart failure. The median parameter estimates from a nonparametric bootstrap procedure were comparable and within 5 % of the estimates from NONMEM. These results provide important information for clinicians to optimize digoxin regimens in elderly patients.

Different effects of dihydropyridine calcium channel antagonists on CYP3A4 enzyme of human liver microsomes.

The present study investigated inhibitory effects of 1,4-dihydropyridines (1,4-DHPs) calcium channel antagonists (1,4-DHP-CCAs) on cytochromeP450 3A4 (CYP3A4) of human liver microsomes and further explored importance of 1,4-DHPs molecular structural descriptors. Partial Least Squares method was applied to probe the quantitative relationships between the 1,4-DHPs molecular structural descriptors and its inhibitory actions, which demonstrated that different 1,4-DHP-CCAs could inhibit CYP3A4 enzyme's activity differently. The K (i) values of nicardipine, lercandipine, cilnidipine, nitrendipine, lacidipine, nifedipine, felodipine were 10.13, 10.17, 11.44, 23.90, 29.34, 29.06 and 32.64 µmol L⁻¹, respectively. It is suggested that the 1,4-DHPs molecular structural descriptors are the most important for its inhibitory effects based on the quantitative structure-activity relationship (QSAR) formula. The LogP was positively correlated to the K (i), whereas molecular weight and molecule volume were negatively correlated. It is concluded that analysis of K (i) of 1,4-DHPs derivatives on the CYP3A4 activity may apply for the QSAR formula at the initial stage of clinical application of new drugs.