Evaluation of intra- and inter-individual variations in plasma belimumab concentrations in adult patients with systemic lupus erythematosus.

In this study, plasma belimumab concentrations were measured over the course of treatment in systemic lupus erythematosus (SLE) patients on belimumab therapy, and intra- and interindividual variations in plasma belimumab concentration were evaluated. A single-center prospective study was conducted at Oita University Hospital to evaluate trough plasma concentrations over the course of treatment in 13 SLE patients treated with intravenous belimumab. Plasma belimumab concentrations were measured by a validated ultra-high performance liquid chromatography with tandem mass spectrometry method. The median age of the patients was 40 (interquartile range: 35-51) years and the median weight was 51.8 (47.0-58.1) kg. A mean of 9.4 (range: 1-13) blood samples was collected per patient at routine visits. The mean (± SD) plasma belimumab concentration was 33.4 ± 11.9 µg/mL in the patient with the lowest concentration and 170.0 ± 16.6 µg/mL in the patient with the highest concentration, indicating a 5-fold difference between patients. On the other hand, the within-patient coefficient of variation ranged from 7.1% to 35.7%, showing no large variations. No significant correlation was observed between plasma belimumab concentration and belimumab dose (mg/kg) (Spearman's rank correlation coefficient = 0.22, p = .54). Examinations of trough plasma belimumab concentrations over the course of treatment in patients with SLE showed small intraindividual variation but large interindividual variation. Plasma belimumab trough concentration varied widely among patients administered the approved dose.

Lack of Interchangeability Between 3 Different Methods for Quantification of Everolimus in Blood: ACMIA, LTIA, and UHPLC-MS/MS.

BACKGROUND: Affinity chrome-mediated immunoassays (ACMIA) do not require pretreatment and have a wide calibration range and good analytical performance. To date, no studies have compared ACMIA and latex agglutination turbidimetry immunoassays (LTIA). The objective of this study was to evaluate the interchangeability of ACMIA, LTIA, and the previously developed ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). METHODS: A total of 111 whole blood samples were collected from 25 patients undergoing routine everolimus therapeutic drug monitoring. The interchangeability between the 3 methods was assessed using robust Passing-Bablok regression analysis and Bland-Altman plots. RESULTS: All samples were quantifiable by UHPLC-MS/MS, whereas 56 and 1 samples were below the lower limits of quantification by LTIA and ACMIA, respectively. In the robust Passing-Bablok regression plots, the slopes of the regression equations between ACMIA and UHPLC-MS/MS, LTIA and UHPLC-MS/MS, and ACMIA and LTIA were 1.23 (95% [confidence interval] CI, 1.13-1.33), 0.67 (95% CI, 0.57-0.77), and 1.71 (95% CI, 1.43-2.33), respectively, with significant proportional biases indicating no interchangeability among all 3 methods. Bland-Altman plots also revealed statistically significant proportional biases between ACMIA and UHPLC-MS/MS (P = 0.012), LTIA and UHPLC-MS/MS (P < 0.001), and ACMIA and LTIA (P < 0.001). CONCLUSIONS: Statistically significant proportional biases were observed among the 3 methods. Blood everolimus concentration measurements should be interpreted with caution when switching the quantification methods for therapeutic drug monitoring.

[Comparison of Preparation Efficiency and Therapeutic Safety between Brand-Name and Generic Products of Pemetrexed].

At Oita University Hospital, we switched our usage of pemetrexed(PEM)from brand-name to generic drugs. We conducted a comparative study of the preparation efficiency and therapeutic safety with the brand-name product and examined the economic effect thereof. The incidence of adverse drug reactions was investigated retrospectively using electronic medical records for patients who received PEM brand-name and generic drugs at our hospital between April 2021 and December 2022. The preparation time per mg was significantly shorter in the generic group at 0.17(0.08-0.38)seconds compared to 0.34(0.15-0.94)seconds for the brand-name group(p<0.01). Regarding the safety comparison, none of the 13 eligible patients developed new hematologic or non-hematologic toxicities of Grade 2 or higher after switching to the generic product. The switch to generics had an economic impact of 7,369,278 yen during the study period. The results suggest that switching from brand-name to generic products is reasonable from the perspectives of therapeutic safety and economic benefits, as well as the expected improvement in preparation efficiency.

Risk Factors for Teicoplanin-Associated Acute Kidney Injury in Patients with Hematological Malignancies: Focusing on Concomitant Use of Tazobactam/Piperacillin.

Patients with hematological malignancies (HM) often receive tazobactam/piperacillin (TAZ/PIPC) and glycopeptide antibiotics for febrile neutropenia. The effect of concomitant use of TAZ/PIPC on risk of teicoplanin (TEIC)-associated acute kidney injury (AKI) remains unclear. We investigated the impact of concomitant TAZ/PIPC use on TEIC-associated AKI in HM patients and identified the risk factors. In this retrospective, single-center, observational cohort study, 203 patients received TEIC, 176 of whom satisfied the selection criteria and were divided into TEIC cohort (no TAZ/PIPC; n = 118) and TEIC + TAZ/PIPC cohort (n = 58). AKI was defined as serum creatinine increase ≥0.3 mg/dL within 48 h or ≥50% from baseline. Incidence of AKI in TEIC cohort before and after propensity score matching was 9.3 and 5.9%, respectively, and that in TEIC + TAZ/PIPC cohort was 10.3 and 11.8%. AKI incidence and risk were not significantly different between two cohorts before (p = 0.829; odds ratio (OR) 1.122, 95% confidence interval (CI) 0.393-3.202) and after matching (p = 0.244; OR 2.133, 95% CI 0.503-9.043). Logistic regression analysis with factors clinically or mechanistically potentially related to TEIC-associated AKI, including concomitant TAZ/PIPC use, as independent variables identified baseline hemoglobin level as the only significant risk factor for TEIC-associated AKI (p = 0.011; OR 0.484, 95% CI 0.276-0.848). In HM patients treated with TEIC, concomitant TAZ/PIPC use did not increase AKI risk whereas lower hemoglobin levels had higher risk for TEIC-associated AKI development, suggesting the necessity to monitor serum creatinine when using TEIC in patients with anemia.

Relationship of plasma 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid concentration with OATP1B activity in patients with chronic kidney disease.

Organic anion-transporting polypeptides (OATP)1B are drug transporters mainly expressed in the sinusoidal membrane. Many studies have suggested that OATP1B activity is affected by genetic factor, the uremic toxin 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), and inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Coproporphyrin-I (CP-I) is spotlighted as a highly accurate endogenous substrate of OATP1B. We previously reported a positive correlation between plasma CMPF and CP-I concentrations in patients with chronic kidney disease (CKD). The present study evaluated the impact of genetic polymorphisms, CMPF, IL-6, TNF-α, and estimated glomerular filtration rate (eGFR) on individual differences in OATP1B activity in patients with CKD. Seventy-three patients with CKD who received kidney transplant at least 3 months earlier were analyzed. Plasma CP-I concentration was higher in OATP1B1*15 carriers than in non-carriers. In all patients, CP-I did not correlate significantly with CMPF, IL-6, TNF-α, or eGFR. However, when the dataset was cut off at CMPF concentration of 8 and 7 µg/mL, 4 µg/mL, 3 µg/mL or 2 µg/mL, CMPF correlated positively with CP-I, and correlation coefficient tended to be higher as plasma CMPF concentration was lower. In conclusion, OATP1B1*15 impacted OATP1B activity in patients with CKD, but IL-6 and TNF-α did not. However, the impact of CMPF on OATP1B activity was limited to low CMPF concentrations, and the effect could be saturated at high concentrations. When prescribing an OATP1B substrate drug for patients with CKD, the OATP1B1*15 carrier status and plasma CMPF concentration may need to be considered to decide the dose regimen.

Evaluation of the usefulness of plasma 4ß-hydroxycholesterol concentration normalized by 4α-hydroxycholesterol for accurate CYP3A phenotyping.

Plasma 4ß-hydroxycholesterol (OHC) has drawn attention as an endogenous substrate indicating CYP3A activity. Plasma 4ß-OHC is produced by hydroxylation by CYP3A4 and CYP3A5 and by cholesterol autoxidation. Plasma 4α-OHC is produced by cholesterol autoxidation and not affected by CYP3A activity. This study aimed to evaluate the usefulness of plasma 4ß-OHC concentration minus plasma 4α-OHC concentration (4ß-OHC-4α-OHC) compared with plasma 4ß-OHC concentration and 4ß-OHC/total cholesterol (TC) ratio in cross-sectional evaluation of CYP3A activity. Four hundred sixteen general adults were divided into 191 CYP3A5*1 carriers and 225 non-carriers. Twenty-six patients with chronic kidney disease (CKD) with CYP3A5*1 allele were divided into 14 with CKD stage 3 and 12 with stage 4-5D. Area under the receiver operating characteristic curve (AUC) for the three indices were evaluated for predicting presence or absence of CYP3A5*1 allele in general adults, and for predicting CKD stage 3 or stage 4-5D in patients with CKD. There was no significant difference between AUC of 4ß-OHC-4α-OHC and AUC of plasma 4ß-OHC concentration in general adults and in patients with CKD. AUC of 4ß-OHC-4α-OHC was significantly smaller than that of 4ß-OHC/TC ratio in general adults (p = 0.025), but the two indices did not differ in patients with CKD. In conclusion, in the present cross-sectional evaluation of CYP3A activity in general adults and in patients with CKD with CYP3A5*1 allele, the usefulness of 4ß-OHC-4α-OHC was not different from plasma 4ß-OHC concentration or 4ß-OHC/TC ratio. However, because of the limitations in study design and subject selection of this research, these findings require verification in further studies.

Usefulness of Belimumab in Adult Patients With Systemic Lupus Erythematosus Evaluated Using Single Indexes: A Meta-Analysis and Systematic Review.

Background: Belimumab is the first antibody drug approved for systemic lupus erythematosus (SLE), and is a fully human monoclonal antibody that inhibits soluble B lymphocyte stimulator protein. In clinical trials, a composite index was used to assess efficacy of belimumab. However, clinical guidelines on SLE treatment currently use single efficacy indexes. Objective: The main objective of this study was to perform a meta-analysis to evaluate the efficacy of belimumab utilizing single indexes used in routine clinical practice, rather than the composite efficacy index used in clinical trials during the development phase. As a secondary endpoint, safety was also evaluated. Methods: Several databases were searched to identify reports published up to December 1, 2021 on randomized controlled trials examining the efficacy of belimumab in adult patients with SLE. From the clinical trial data, efficacy was evaluated using single indexes including the SLE Disease Activity Index (SLEDAI), British Isles Lupus Assessment Group Index, and Physician Global Assessment. Safety was also assessed. Data were synthesized and analyzed using Review Manager 5.4. This study protocol was registered in the UMIN Clinical Trials Registry (Registration number: UMIN000052846). Results: The search identified 12 reports that met the inclusion criteria. Five reports were included in efficacy evaluation and 9 in safety evaluation. The primary endpoint was SLEDAI. Significantly more belimumab-treated patients achieved a ≥4-point reduction in SLEDAI (relative risk 1.28; 95% confidence interval, 1.16-1.40; P < 0.00001) compared with placebo. Other efficacy endpoints were also improved significantly in the belimumab group. No difference in safety was found between belimumab and placebo. Conclusions: The present meta-analysis evaluating clinical trial data using various single indexes recommended by clinical guidelines for SLE verifies that addition of belimumab to standard of care is efficacious for moderate-to-severe SLE.

Rapid and simple quantification of belimumab in human plasma using ultra-high performance liquid chromatography with tandem mass spectrometry.

OBJECTIVE: Belimumab is a monoclonal antibody against the B-lymphocyte stimulating factor and is approved for the treatment of patients with systemic lupus erythematosus (SLE) not responding adequately to existing therapies. In this study, we established and validated an assay for quantifying belimumab in human plasma. METHODS: From the peptides generated by trypsin digestion of belimumab, in silico analysis was used to search for unique peptides to determine the surrogate peptides. Samples were trypsin digested, pretreated with solid phase extraction, and analyzed by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) to quantify the surrogate peptide in the samples. The assay was validated according to the Food and Drug Administration (FDA) bioanalytical method validation guidance. We used the established assay to quantify plasma belimumab concentrations in two SLE patients treated with belimumab. RESULTS: Among the unique peptides identified by the in silico analysis, the peptide with the best peak shape when measured by UHPLC-MS/MS was selected as the surrogate peptide. The validation results of this assay met the acceptable criteria recommended by the FDA guidance. The lower limit of quantification (LLOQ) for belimumab was 2 µg/mL. Recovery rates and matrix effects when corrected for internal standards were 91.5-114.3 % and 96.9-108.4 %, respectively. Plasma concentrations of belimumab were measured in 12 samples from two belimumab-treated SLE patients. All concentrations were within the calibration range. CONCLUSIONS: We have established and validated a method for measuring plasma belimumab concentrations using UHPLC/MS-MS. By measuring plasma belimumab concentrations in more patients, this method is expected to contribute to appropriate use of belimumab.

Comparison of Incidence of Hyponatremia between Linezolid and Vancomycin by Propensity Score Matching Analysis.

Several cases of severe hyponatremia induced by linezolid (LZD) were reported. However, severe infections could also cause hyponatremia by increasing vasopressin secretion. To prove that hyponatremia is associated with LZD rather than infection, we compared the incidence and risk of developing hyponatremia between patients receiving LZD and those receiving vancomycin (VCM). A retrospective, single-center, observational cohort study was conducted in patients aged 18 years or older who received intravenous LZD or VCM for 7 d or longer. Hyponatremia was defined as serum sodium level lower than 134 mEq/L and more than 5% decrease from baseline after treatment initiation. The incidence and risk of developing hyponatremia were analyzed between LZD and VCM groups using chi-square test. Four hundred and fifty patients who satisfied the selection criteria were divided into LZD (n = 97) and VCM groups (n = 353). Significant differences in patient characteristics between LZD and VCM groups were observed before propensity score matching, but no significant differences were found after matching. LZD group showed a significantly higher incidence and risk of developing hyponatremia compared to VCM group both before (LZD: 16.5%, VCM: 5.4%; p < 0.001, odds ratio 3.472 [95% confidence interval (CI) 1.711-7.048]) and after (LZD: 17.8%, VCM: 5.5%; p = 0.020, odds ratio 3.738 [95% CI 1.157-12.076]) propensity score matching. In conclusion, propensity score analyses suggest that the risk of hyponatremia associated with LZD is approximately 3.7-fold higher than that associated with VCM, regardless of patient background.

A Questionnaire Survey of Prescription Preferences and Leftover Medication Conversations: Comparisons Among Kidney Disease Patients and Healthcare Professionals.

BACKGROUND: Patients with chronic kidney disease (CKD) and patients with kidney failure receiving hemodialysis (HD) receive various types of medications. However, little is known about the differences in medication preference and how to deal with leftover medication among CKD patients and HD patients. The purpose of this study was to investigate the differences in medication preference and ways of dealing with leftover medication between CKD patients, HD patients, physicians, and pharmacists via a questionnaire survey. METHODS: The ethics committee of Oita University, Oita, Japan, approved this survey. Outpatients undergoing treatment by a nephrologist in four facilities in Oita prefecture, Japan, were asked to answer a questionnaire on their preference for medication and how to deal with leftover medication. Respondents gave their informed written consent. The same questionnaire was administered to nephrologists and pharmacists online. RESULTS: In this survey, 383 patients (260 patients with CKD and 123 patients with HD), 22 nephrologists, and 28 pharmacists responded. The response rate of valid responses was more than 90% for each of the groups. In particular, 41% of patients with CKD and 56% of patients with HD never inform their doctor about leftover medication or only inform them when there is a lot of leftover medication. On the other hand, 23% of physicians have never asked their patients about them. Ordinary logistic regression analysis indicated that there is no significant relationship between how often patients talk about leftover medication, patients' preferences, or patient states. CONCLUSIONS: Despite the age and state of the patients, it is important to discuss the perception of medication with each other and confirm the condition of the remaining medication to improve concordance and obtain the desired treatment effect.

Evaluation of effects of indoxyl sulfate and parathyroid hormone on CYP3A activity considering the influence of CYP3A5 gene polymorphisms.

AIMS: Indoxyl sulfate and parathyroid hormone (PTH), which accumulate in chronic kidney disease (CKD), have been reported to reduce cytochrome P450(CYP)3A activity. Homozygotes of the CYP3A5*3 allele have reduced CYP3A5 activity compared to carriers of at least one CYP3A5*1 allele. 4ß-Hydroxycholesterol (4ß-OHC) has been established as an endogenous substrate reflecting CYP3A activity. 4ß-OHC is produced through hydroxylation by CYP3A4 and CYP3A5 and by autoxidation of cholesterol, whereas 4α-hydroxycholesterol (4α-OHC) is produced solely by autoxidation of cholesterol. This study focused on CKD patients and evaluated the effects of plasma indoxyl sulfate and intact-PTH concentrations on plasma 4ß-OHC concentration, 4ß-OHC/total cholesterol ratio and 4ß-OHC-4α-OHC, with consideration of the influence of CYP3A5 polymorphism. METHODS: Sixty-three CKD patients were analysed and divided into CYP3A5 carrier group (n = 26) and non-carrier group (n = 37). RESULTS: Plasma indoxyl sulfate significantly correlated inversely with 4ß-OHC concentration and with 4ß-OHC-4α-OHC in both the CYP3A5*1 carrier group (r = -0.42, P = .034; r = -0.39, P = .050, respectively) and the non-carrier group (r = -0.45, P = .0054; r = -0.39, P = .019, respectively). However, multiple regression analysis did not identify plasma indoxyl sulfate concentration as a significant independent factor associated with any of the CYP3A activity indices. There was no significant correlation between plasma intact-PTH concentration and any of the CYP3A activity indices. CONCLUSIONS: The present results suggest that plasma indoxyl sulfate and intact-PTH concentrations do not have clinically significant effects on CYP3A activity in patients with CKD.

Positive correlation between organic anion transporter 1B function indicated by plasma concentration of coproporphyrin-I and blood concentration of cyclosporin A in real-world patients.

AIMS: Cyclosporin A (CyA) has potent inhibitory activity on organic anion transporting polypeptide 1B (OATP1B), causing drug-drug interactions with its substrate drugs. 3-carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF), a uraemic toxin, has also been suggested to inhibit OATP1B activity. Recent study has identified coproporphyrin-I (CP-I) as a specific endogenous substrate for OATP1B, which is useful to indicate OATP1B activity. We investigated the relationship of CP-I with CyA and CMPF concentrations in patients taking CyA. METHODS: In total, 121 blood samples from 74 patients who took CyA and underwent routine therapeutic drug monitoring were divided into trough and peak samples. RESULTS: CyA and CP-I concentrations were significantly higher in peak samples than in trough samples. A positive correlation between CP-I and CyA concentrations was found in all samples and in trough and peak samples, while no correlation was observed between CP-I and CMPF concentrations. Multiple regression analysis identified CyA and C-reactive protein concentrations as independent factors affecting CP-I concentration, with blood CyA concentration having markedly greater contribution to plasma CP-I concentration. CONCLUSION: The present study suggests that CyA inhibits OATP1B activity in a concentration-dependent manner in clinical setting, and that dose adjustment of OATP1B substrate drugs coadministered with CyA according to plasma CMPF concentration may not be necessary.

UHPLC-MS/MS method for simultaneous quantification of doripenem, meropenem, ciprofloxacin, levofloxacin, pazufloxacin, linezolid, and tedizolid in filtrate during continuous renal replacement therapy.

BACKGROUND: Since severe infections frequently cause acute kidney injury (AKI), continuous renal replacement therapy (CRRT) is often initiated for regulation of inflammatory mediators and renal support. Thus, it is necessary to decide the antibiotic dosage considering the CRRT clearance in addition to residual renal function. Some of the hemofilters used in CRRT are known to adsorb antibiotics, and clearance of antibiotics may differ depending on the adsorptive characteristics of hemofilters. Although assay systems for blood and CRRT filtrate concentrations are required, no method for measuring antibiotics concentrations in filtrate has been reported. We developed a UHPLC-MS/MS method for simultaneous quantification of antibiotics commonly used in ICU, comprising carbapenems [doripenem (DRPM) and meropenem (MEPM)], quinolones [ciprofloxacin (CPFX), levofloxacin (LVFX) and pazufloxacin (PZFX)] and anti-MRSA agents [linezolid (LZD), and tedizolid (TZD)] in CRRT filtrate samples. METHODS: Filtrate samples were pretreated by protein precipitation. The analytes were separated with an ACQUITY UHPLC CSH C18 column under a gradient mobile phase consisting of water and acetonitrile containing 0.1% formic acid and 2 mM ammonium formate. RESULTS: The method showed good linearity over wide ranges. Within-batch and batch-to-batch accuracy and precision for each drug fulfilled the criteria of the US Food and Drug Administration guidance. The recovery rate was more than 87.20%. Matrix effect ranged from 99.57% to 115.60%. Recovery rate and matrix effect did not differ remarkably between quality control samples at different concentrations. CONCLUSION: This is the first report of a simultaneous quantification method of multiple antibiotics in filtrate of CRRT circuit.

Impact of Inflammation on Intra-individual Variation in Trough Voriconazole Concentration in Patients with Hematological Malignancies.

The pharmacokinetics of voriconazole shows large intra-individual and inter-individual variability and is affected by various factors. Recently, inflammation has been focused as a significant factor affecting the variability. This study aimed to compare the influence of C-reactive protein (CRP) and other clinical laboratory parameters on intra-individual variability in trough voriconazole concentration and examine the impact of inflammation in patients with hematological malignancies. We conducted a retrospective, single-center, observational cohort study. Forty-two patients with hematological malignancy who received oral voriconazole for prophylaxis against deep mycosis and underwent multiple measurements of trough plasma voriconazole concentration were recruited. Quantitative changes in pharmacological and clinical laboratory parameters (Δ) were calculated as the difference between the current and preceding measurements. Voriconazole concentration/maintenance dose per weight (C/D) was found to correlate positively with CRP level (n = 202, rs = 0.314, p < 0.001). Furthermore, ΔC/D correlated positively with ΔCRP level (n = 160, rs = 0.442, p < 0.001), and ΔCRP showed the highest correlation coefficient among the laboratory parameters. Univariate and multivariate analyses identified ΔCRP (p < 0.001) and Δgamma-glutamyl transpeptidase (γGTP) (p = 0.019) as independent factors associated with ΔC/D. Partial R2 were 0.315 for ΔCRP and 0.024 for ΔγGTP, suggesting markedly greater contribution of ΔCRP to ΔC/D. In conclusion, since clinical laboratory parameters other than CRP had little influence on trough plasma voriconazole concentration, therapeutic drug monitoring and dose adjustment considering fluctuation in CRP level would be important for proper use of voriconazole in patients with hematological malignancies.

Association of Vancomycin Trough Concentration and Clearance With Febrile Neutropenia in Pediatric Patients.

BACKGROUND: Febrile neutropenia promotes renal drug excretion. Adult and pediatric patients with febrile neutropenia exhibit a lower vancomycin concentration/dose (relative to bodyweight) ratio than those with other infections. In pediatric patients, renal function relative to bodyweight varies depending on age, and vancomycin clearance is age dependent. This study aimed to analyze the effects of febrile neutropenia on the pharmacokinetics of vancomycin in age-stratified pediatric patients. METHODS: This retrospective, single-center, observational cohort study analyzed 112 hospitalized pediatric patients who met the selection criteria and intravenously received vancomycin at the Department of Pediatrics of the Oita University Hospital between April 2011 and October 2019. RESULTS: The febrile neutropenia (n = 46) cohort exhibited a significantly higher estimated glomerular filtration rate than the nonfebrile neutropenia (n = 66) cohort. Compared with those in the nonfebrile neutropenia cohort, the daily vancomycin dose relative to bodyweight and vancomycin clearance were significantly higher, and the vancomycin trough concentration and vancomycin concentration/dose ratio were significantly lower in the febrile neutropenia cohort. In the age groups of 1-6 and 7-12 years, compared with those in the nonfebrile neutropenia cohort, the vancomycin concentration/dose ratio was significantly lower, and vancomycin clearance was significantly higher in the febrile neutropenia cohort. Univariate and multivariate analyses identified febrile neutropenia as the independent factor influencing vancomycin concentration/dose ratio and clearance only in pediatric patients aged 1-6 years. CONCLUSIONS: Increased initial dosage and therapeutic drug monitoring-guided dose optimization are critical for the therapeutic efficacy of vancomycin in pediatric patients with febrile neutropenia, especially in those aged 1-6 years.

A validated UHPLC-MS/MS method for quantification of total and free tedizolid concentrations in human plasma.

Tedizolid (TZD) is a novel oxazolidinone antibiotic. Although TZD efficacy correlates with area under the concentration-time curve/minimum inhibitory concentration, there is no report of pharmacokinetic/pharmacodynamic analysis using plasma free TZD concentrations. Several methods have been developed for measuring total TZD concentration, but not for free TZD concentration. We aimed to develop a high-throughput simultaneous quantification method for total and free TZD concentrations using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). The equilibrium dialysis method was used for separation of the free fraction. Pretreatment was conducted by solid-phase extraction using 96-well HLB µElution plate. Chromatographic separation of the analytes was conducted using a C18 column. MS/MS transitions were monitored in the positive ion mode. Full validation was performed in accordance with the bioanalytical method validation guidance prepared by the US Food and Drug Administration (FDA). The assay showed good linearity over wide ranges of 5-5000 (r2 = 0.9964) and 1.5-1500 (r2 = 0.9990) ng/mL for total and free TZD concentrations, respectively. Within-batch accuracy and precision as well as batch-to-batch accuracy and precision for total and free concentrations fulfilled the criteria of the FDA guidance. The recovery rates were higher than 92.3% and higher than 85.3% for total and free concentrations. Matrix effect showed no remarkable differences among three quality control levels for total and free concentrations. In vitro protein binding rates of TZD ranged from 71.6% to 76.9%, indicating no concentration-dependent difference within the calibration ranges. The total and free concentrations in five patients who received TZD were within the ranges of the calibration curves, demonstrating the feasibility of clinical application of the novel method. In conclusion, we have succeeded to develop for the first time a method for simultaneous quantification of total and free TZD concentrations.

Sustained suppression of enterohepatic circulation of mycophenolic acid by antimicrobial-associated diarrhea in a kidney transplant recipient with Crohn's disease: A case report.

Mycophenolic acid (MPA) undergoes enterohepatic circulation. A kidney transplant patient on mycophenolate mofetil was treated with tazobactam/piperacillin for pyelonephritis, and developed antimicrobial-associated diarrhea. Consequently, the MPA trough level decreased by approximately 90%. Furthermore, it took approximately a month for the MPA level to normalize even after diarrhea had resolved.

High-Sensitivity and High-Throughput Quantification of Everolimus in Human Whole Blood Using Ultrahigh-Performance Liquid Chromatography Coupled With Tandem Mass Spectrometry.

BACKGROUND: Rigorous dose adjustment by therapeutic drug monitoring (TDM) is recommended when everolimus (EVR) is administered for immunosuppression. In this study, the authors developed a highly sensitive ultrahigh-performance liquid chromatography coupled with the tandem mass spectrometry (UHPLC-MS/MS) method for measuring EVR concentrations in whole blood using a high-throughput solid-phase extraction method for sample pretreatment. Furthermore, the blood EVR concentrations in routine TDM samples from patients who underwent renal transplantation measured using the established UHPLC-MS/MS method were compared with those measured using the latex agglutination turbidimetric immunoassay (LTIA). METHODS: Blood samples were pretreated by solid-phase extraction using a 96-well HLB µElution plate. The clinical application of the newly developed method was evaluated using 87 blood samples from 19 patients who underwent kidney transplant. RESULTS: The calibration curve showed good linearity over a wide range of 0.1-50 ng/mL, with relative error ≤15% obtained from the back calculation of calibrators, and ≤20% for the lower limit of quantification. Within-batch and batch-to-batch accuracies and precisions fulfilled the acceptance criteria of the US Food and Drug Administration guidelines for bioanalytical method validation. The extraction recovery rates were good (≥65.2%), and almost no matrix effects were found in any of the quality control samples. Blood EVR concentrations measured by UHPLC-MS/MS were positively correlated with those measured by LTIA. A Bland-Altman plot indicated that the UHPLC-MS/MS method yielded better measurements than the LTIA method, regardless of the concentration. CONCLUSIONS: Therefore, the authors succeeded in developing a novel high-sensitivity and high-throughput method for measuring blood EVR concentration by UHPLC-MS/MS using a µElution plate for sample pretreatment.

Highly sensitive simultaneous quantification of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid in human plasma using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry.

Indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid are uremic toxins that accumulate in renal failure and have been reported to decrease the activities of the drug-metabolizing enzyme cytochrome P450 3A and the drug transporter organic anion transporting polypeptides 1B, respectively. In this study, we established and validated an assay for simultaneous quantification of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid in human plasma. The samples were pretreated by solid-phase extraction, and measured by ultra-high-performance liquid chromatography-tandem mass spectrometry. The validation results for this assay were within the acceptable limits recommended by the US Food and Drug Administration, with a lower limit of quantitation of 0.05 µg/mL for both indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid. Recovery rates of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid corrected by internal standard were 100.7-101.9 and 100.2-101.3%, respectively. Matrix effects of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid corrected by internal standard were 101.1-105.5 and 97.0-103.8%, respectively. The validated assay was used to analyze indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid concentrations in the plasma samples of healthy volunteers and patients with chronic kidney disease. All the measured plasma indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid concentrations were within the calibration ranges. This novel method may contribute to predicting the activities of drug-metabolizing enzymes and drug transporters in individual patients.