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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).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.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.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.

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 R

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.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.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.This is the first report of a simultaneous quantification method of multiple antibiotics in filtrate of CRRT circuit.

What is known and objective Clinical cases of attenuation of opioid analgesic effect by administration of immune checkpoint inhibitors has not been reported. We present a case of head and neck cancer under pain management with opioids, in which cancer pain was exacerbated after administration of nivolumab. Case summary A male patient with head and neck cancer was hospitalized for the second-line treatment of nivolumab. He had complained of head and neck pain after admission, but the pain was especially worse after nivolumab administration. The dose of opioids was eventually increased by approximately 320% (morphine equivalent dose) compared to before administering nivolumab. What is new and conclusion When administering immune checkpoint inhibitors such as nivolumab in clinical practice, the possibility of attenuation of opioid analgesic effect should be considered.

Background Lenvatinib is increasingly being selected as the first-line treatment for unresectable hepatocellular carcinoma (HCC) based on the results of the REFLECT trial. However, early discontinuation of lenvatinib because of adverse effects is a frequent occurrence. Hence, lenvatinib is a difficult drug for use in the clinical setting. One of the causes is that the dose of lenvatinib is mainly determined by body weight alone, despite high interindividual variability. To overcome this problem, a dosing regimen of lenvatinib based on a population pharmacokinetic (PPK) model for HCC patients is proposed. The aim of this study was to develop a high-throughput quantification method for lenvatinib using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) that can be applied to a PPK analysis of HCC patients in the future. Methods After a simple solid-phase extraction step using a 96-well plate, lenvatinib was analyzed by UHPLC-MS/MS in a positive electrospray ionization mode. Results The novel method fulfilled the requirements of the US Food and Drug Administration guidance on bioanalytical method validation. The calibration curve was linear over the 0.2-1000 ng/mL concentration range. The average recovery rate was 98.63 ± 4.55% (mean ± SD). The precision was below 6.05%, and the accuracy was within 12.96% for all quality control levels. The matrix effect varied between 103.33% and 134.61%. This assay was successfully applied to the measurement of plasma concentrations in 6 HCC patients receiving lenvatinib. Conclusions A novel high-throughput UHPLC-MS/MS assay for quantification of lenvatinib in human plasma was successfully developed. This method can be applied to PPK analysis for patients receiving lenvatinib in the clinical setting.

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.In total, 121 blood samples from 74 patients who took CyA and underwent routine therapeutic drug monitoring were divided into trough and peak samples.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.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.

For intensive care unit (ICU) patients, injectable voriconazole (VRCZ) is difficult to use because the patients often develop acute kidney injury. Since many ICU patients have consciousness disturbance, oral ingestion of tablet formulation is also difficult, and administration of a suspension via enteral feeding tube is required when using VRCZ. In this study, we investigated the in vitro adsorption property of oral VRCZ to feeding tube and performed pharmacokinetic analysis of VRCZ prepared by powdering and simple suspension for ICU patients. VRCZ was tube-administered to five ICU patients at a loading dose of 300 mg and plasma VRCZ concentrations before and at 1, 2, 4, 8, 12 h after the first dose were measured using HPLC. Pharmacokinetic parameters were calculated by non-compartmental model analysis. The recovery rate of VRCZ after infusion of the suspension through feeding tube was 89.8 ± 8.3%, but the cumulative rates after the first and second re-infusion were 102.7 ± 20.7 and 99.3 ± 10.3%, respectively, suggesting almost no residual drug in the tube after re-infusion. Metabolic phenotype was extensive metabolizer (EM) in two patients and intermediate metabolizer (IM) in three patients. The values of total clearance (CLtot/F) calculated by moment analysis were 0.51 and 0.55 L/h/kg in two EM patients, and 0.09, 0.29 and 0.31 L/h/kg in three IM patients. The CLtot/F was apparently lower in IM patients compared to EM. In conclusion, powdered and suspended VRCZ administered via enteral feeding tube showed pharmacokinetics depending on CYP2C19 gene polymorphism, similar to that observed in usual oral administration.

Objectives Critically ill patients in intensive care unit (ICU) are susceptible to infectious diseases, thus empirical therapy is recommended. However, the therapeutic effect in ICU patients is difficult to predict due to fluctuation in pharmacokinetics because of various factors. This problem can be solved by developing personalized medicine through therapeutic drug monitoring. However, when different measurement systems are used for various drugs, measurements are complicated and time consuming in clinical practice. In this study, we aimed to develop an assay using ultra-high performance liquid chromatography coupled with tandem mass spectrometry for simultaneous quantification of 12 antimicrobial agents commonly used in ICU: doripenem, meropenem, linezolid, tedizolid, daptomycin, ciprofloxacin, levofloxacin, pazufloxacin, fluconazole, voriconazole, voriconazole N-oxide which is a major metabolite of voriconazole, and posaconazole. Design & methods Plasma protein was precipitated by adding acetonitrile and 50% MeOH containing standard and labeled IS. 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 fulfilled the criteria of US Food and Drug Administration for assay validation. The recovery rate was more than 84.8%. Matrix effect ranged from 79.1% to 119.3%. All the calibration curves showed good linearity (back calculation of calibrators: relative error ≤ 15%) over wide concentration ranges, which allowed determination of Cmax and Ctrough. Clinical applicability of the novel method was confirmed. Conclusions We have developed an assay for simultaneous quantification of 12 antimicrobial agents using a small sample volume of 50 μL with a short assay time of 7 min. Our novel method may contribute to simultaneous calculation of pharmacokinetic and pharmacodynamic parameters.

Drug‐drug interaction of fluorinated pyrimidine anticancer agents with phenytoin is well known, but interaction with phenobarbital is limited. We describe a case showing increases in plasma phenobarbital as well as phenytoin concentrations during preoperative S‐1 (tegafur/gimeracil/oteracil) and radiation therapy for rectal cancer., When used in combination with a fluorinated pyrimidine anticancer drug such as S‐1, the blood level of PB as well as PHT may increase. In order to avoid adverse events due to this interaction, confirmation for the blood levels of PHT and PB by TDM is essential.

Free itraconazole and hydroxyitraconazole concentrations were markedly elevated despite almost no changes in total concentrations when itraconazole was discontinued due to adverse effects. Elevated free itraconazole concentration may have a causal relationship with the development of adverse effects.

What is known and objective Thrombocytopenia is one of the typical adverse events caused by linezolid (LZD). Recently, some cases of severe hyponatraemia occurring while receiving LZD have been reported. This study investigated a possible relationship between LZD-induced hyponatraemia and thrombocytopenia and identified the risk factors for hyponatraemia and/or thrombocytopenia. Methods In this retrospective, single-centre, observational cohort study, 63 hospitalized patients aged over 18 years who received intravenous injection of LZD for more than seven consecutive days in Oita University Hospital between April 2015 and March 2018 were analysed. Results Thrombocytopenia occurred in 25 (39.7%) patients and hyponatraemia in 11 (17.5%) patients. Seven of 11 patients with hyponatraemia had concurrent thrombocytopenia. Although both serum sodium level and platelet count declined in most patients who developed hyponatraemia, no significant association between thrombocytopenia and hyponatraemia was found. Creatinine clearance level (Ccr) was significantly lower not only in the thrombocytopenia (vs no-thrombocytopenia) but also in the hyponatraemia group (vs no-hyponatraemia group). Univariate and multivariate logistic regression analyses identified different risk factors for thrombocytopenia and/or hyponatraemia (thrombocytopenia: Ccr and administration period; hyponatraemia: serum albumin; thrombocytopenia and hyponatraemia: administration period and serum albumin). What is new and conclusion In conclusion, this study found no significant relationship between LZD-induced thrombocytopenia and hyponatraemia and identified some possible risk factors associated with onset of the two adverse events. These require further validation.

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 (r

At the Oita University Hospital, we switched from using the original biological product of trastuzumab(original product) to a biosimilar product, and verified the appropriateness of the switch by investigating the occurrence of adverse events. We compared the safety of the original and biosimilar products from January 2019 to September 2020. Of 14 cases studied, there were 6 in the original product group, 6 in the switched group, and 2 in the biosimilar group. In 3 patients in the switched group, infusion reaction was observed during administration of the original product, and was appropriately managed at that time. After switching to the biosimilar product, it was possible to administer the drug safely even when the infusion time was shortened. The results of this study showed that no adverse events were observed after switching from the original to the biosimilar product. This finding suggests that switching products is appropriate, not only from an economic point of view but also from the perspective of treatment safety.

Background: Although lenvatinib treatment has a favorable efficacy for unresectable hepatocellular carcinoma (HCC), it is associated with adverse events (AEs) that must be closely monitored and managed. Thrombocytopenia is one of the major AEs. The aim of this study was to clarify whether thrombocytopenia can be predicted by the plasma concentration of lenvatinib. Methods: This was a single-center retrospective observational study. Twenty-three patients with unresectable HCC and pharmacokinetics data at the initial lenvatinib administration between May 2018 and September 2020 at Oita University Hospital were enrolled. The AEs during the 4 weeks after the initiation of treatment were evaluated, and the correlations between the thrombocytopenia and the plasma concentration of lenvatinib were examined. Spearman’s correlation was used to evaluate the correlation between two continuous variables. Results: The rate of platelet count decrease correlated with the maximum plasma concentration (C max ) (r = 0.65, P = 0.001), whereas it did not with the minimum plasma concentration (C min ) (r = 0.29, P = 0.206). After stepwise multiple linear regression analysis, the starting dose of lenvatinib and the serum albumin concentration were identified as independent explanatory variables. Next, a formula for predicting the C max using these two variables was created. The predicted C max was strongly correlated with the C max (r = 0.87, P < 0.0001) and the rate of platelet count decrease (r = 0.67, P = 0.001). Conclusions: This study identified the usefulness of the drug C max to predict the rate of platelet count decrease within 4 weeks after the initiation of treatment. Although it is difficult to measure the plasma concentration of lenvatinib in community hospitals, the predicted C max is useful for predicting the rate of platelet count decrease with this treatment. World J Oncol. 2021;12(5):165-172 doi: https://doi.org/10.14740/wjon1399

Objectives For patients with hematological malignancy, triazole antifungal agents such as fluconazole (FLCZ), itraconazole (ITCZ), voriconazole (VRCZ), posaconazole (PSCZ) and isavuconazole (ISCZ) are often used for prophylaxis of deep mycosis. Since these azoles exhibit large pharmacokinetic variability, dose adjustment by therapeutic drug monitoring is recommended for some azoles. This study aimed to develop and validate a novel method for simultaneous determination of plasma concentrations of FLCZ, ITCZ, VRCZ, PSCZ, ISCZ and ITCZ-OH, an active metabolite of ITCZ, using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). Design & methods A high-throughput solid-phase extraction method using 96-well MCX µElution Plate was selected as the pretreatment procedure. Results The calibration curves for FLCZ, ITCZ, ITCZ-OH, VRCZ, PSCZ and ISCZ showed good linearity (back-calculation of calibrators: relative error ≤ 15% [LLOQ: ≤ 20%]) over wide ranges of 100–100000, 20–20000, 40–40000, 20–20000, 5–5000 and 50–50000 ng/mL, respectively. The validation results of all six drugs fulfilled the criteria of the guidance for bioanalytical method validation of the US Food and Drug Administration for within-batch and batch-to-batch precision and accuracy. The extraction recovery rates were good at ≥ 74.9%, and almost no matrix effects were found for all the drugs. The trough (10 h post-dose in 1 patient on PSCZ) drug concentrations in patients with hematologic malignancy who received oral FLCZ, ITCZ, VRCZ or PSCZ were quantified using the method developed. The measurements for all samples were within the ranges of the calibration curves, demonstrating the feasibility of clinical application of the novel method. Conclusions We have succeeded in developing a novel high-throughput method using UHPLC-MS/MS for simultaneous quantification of plasma concentrations of FLCZ, ITCZ, ITCZ-OH, VRCZ, PSCZ and ISCZ.

Organic anion transporting polypeptides (OATPs) 1B are drug transporters mainly expressed in the sinusoidal membrane. In previous reports, genetic factor, 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), which is one of the uremic toxins, inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) decreased OATP1B1 activity in vitro, but in vivo effects of these factors have not been elucidated. Plasma coproporphyrin-I (CP-I) is spotlighted as a highly accurate endogenous substrate of OATP1B. This study focused on patients with rheumatoid arthritis (RA) and evaluated the influence of several factors comprising gene polymorphisms, uremic toxins, and inflammatory cytokines on OATP1B activity using plasma CP-I concentration. Thirty-seven outpatients with RA who satisfied the selection criteria were analyzed at the time of recruitment (baseline) and at the next visit. OATP1B1*15 carriers tended to have higher CP-I concentration compared with noncarriers. Plasma CP-I correlated positively with CMPF concentration, but did not correlate with IL-6 or TNF-α concentration. Multiple logistic regression analysis by stepwise selection identified plasma CMPF concentration and OATP1B1*15 allele as significant factors independently affecting plasma CP-I concentration at baseline and at the next visit, respectively. In conclusion, the present results suggest that inflammatory cytokines do not have clinically significant effects on OATP1B activity, whereas the effects of genetic polymorphisms and uremic toxins should be considered.

Because either trough or peak concentration at 2 h after administration is measured in routine therapeutic drug monitoring for cyclosporine A (CyA), a quantification method with a wide-range calibration curve capable of simultaneously measuring both concentrations is required. We developed a sensitive, wide-range and high-throughput quantification method for CyA in whole blood using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and compared patients' blood CyA levels measured by UPLC-MS/MS and antibody-conjugated magnetic immunoassay (ACMIA). Whole blood samples were prepared by solid-phase extraction using Oasis HLB μElution plate. The UPLC-MS/MS assay showed excellent linearity over a wide calibration range of 5-2500 ng/mL. Within-batch accuracy and precision as well as batch-to-batch accuracy and precision fulfilled the criteria of US Food and Drug Administration guidelines. The blood CyA concentrations measured by the UPLC-MS/MS assay correlated strongly with those measured by ACMIA. A Bland-Altman plot showed a fixed error between CyA concentrations measured by the two methods, and the concentrations measured by the UPLC-MS/MS method were consistently lower than those measured by ACMIA. We have succeeded to develop a sensitive, wide-range and high-throughput quantification method for CyA in whole blood using UPLC-MS/MS.

Background Pazopanib is widely used to treat renal cell carcinomas and soft tissue tumors in Japan. Pazopanib has significant therapeutic efficacy but it is associated with frequent severe adverse effects. Therapeutic drug monitoring (TDM) may help to prevent adverse effects. A more convenient and rapid pazopanib assay is desirable for the application of TDM in clinical settings. In this study, the authors developed a high-throughput method for quantifying pazopanib in human plasma using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Methods After a simple solid-phase extraction step using a 96-well plate, pazopanib was analyzed by UHPLC-MS/MS in the positive electrospray ionization mode. Results The novel method fulfilled the requirements of the US Food and Drug Administration and the European Medicines Agency guidelines for assay validation, and the lower limit of quantification was 0.5 mcg/mL. The calibration curves were linear over the concentration range of 0.5-100 mcg/mL. The average recovery rate was 102.0% ± 3.9% (mean ± SD). The precision was below 5.0%, and the accuracy was within 12.0% for all quality control levels. Matrix effect varied between 90.9% and 97.1%. This assay was successfully applied to TDM of pazopanib trough concentrations in 3 patients treated with the drug for soft tissue tumors. Conclusions The authors succeeded in developing a novel high-throughput UHPLC-MS/MS method for quantifying pazopanib in human plasma. This method can be applied to TDM of patients receiving pazopanib in clinical settings.

Pazopanib is widely used to treat renal cell carcinomas and soft tissue tumors in Japan. Although several reports demonstrated the usefulness of therapeutic drug monitoring (TDM) of pazopanib, those studies measured only total pazopanib concentration. For drugs with high protein binding rates such as pazopanib, measuring free concentrations may be clinically more useful than measuring total concentrations. In this study, we aimed to develop a high-throughput method for quantification of free pazopanib in human plasma using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Free pazopanib was separated by ultrafiltration. After a simple solid-phase extraction step using a 96-well plate, pazopanib was analyzed by UHPLC-MS/MS in positive electrospray ionization mode. The novel method fulfilled the requirements of the US Food and Drug Administration guidelines for assay validation, and the lower limit of quantification was 0.05 ng/mL. The calibration curve was linear over the concentration range of 0.05–50 ng/mL. The average recovery rate was 66.9 ± 2.1% (mean ± SD). The precision was below 7.02%, and accuracy was within 10.60% across all quality control levels. Matrix effect varied between 44.4% and 60.4%. This assay was successfully applied to measure trough free pazopanib concentrations in three patients treated with pazopanib for soft tissue tumors. We succeeded to develop a novel high-throughput UHPLC-MS/MS method for quantification of free pazopanib in human plasma. This method can be applied to TDM for patients receiving pazopanib in the clinical setting.

Several recent studies on pharmacokinetics of linezolid (LZD) and daptomycin (DAP) reported that plasma concentration was linked to efficacy and adverse effects, suggesting the usefulness of therapeutic drug monitoring (TDM). The usefulness of TDM for tedizolid (TZD) has not been reported, but a previous report showed individual differences in area under the curve depending on body weight. In intensive care unit (ICU) patients, pharmacokinetics was reported to fluctuate due to various factors. Here, we developed a high-throughput and wide-range simultaneous quantification method for LZD, DAP and TZD in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Plasma samples were pretreated by solid-phase extraction using Oasis® HLB μElution Plate. The assay fulfilled the requirements of US Food and Drug Administration and the European Medicines Agency for bioanalytical method validation. The assay for LZD, DAP and TZD showed good linearity over wide ranges of 100−100000, 150−150000 and 5−5000 ng/mL, respectively. Within-batch accuracy and precision as well as batch-to-batch accuracy and precision for all three drugs fulfilled the criteria of the above guidance. Extraction recovery rates were more than 92.2 % for LZD, 44.7 % for DAP, and 84.8 % for TZD. Matrix effect showed no remarkable differences among low, medium and high quality control samples for the three drugs. The maximum and trough concentrations of three patients each who received LZD, DAP or TZD in ICU were measured by the novel UPLC-MS/MS method. In all patients, the measured concentrations 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 the first method for simultaneous quantification of plasma concentrations of LZD, DAP and TZD.