A Prospective Study on the Usefulness of Initial Voriconazole Dose Adjustment Based on CYP2C19 Gene Polymorphism Analysis

Genetic polymorphism exists for CYP2C19, a dominant metabolic enzyme of voriconazole (VRCZ), and VRCZ pharmacokinetics has been shown to fluctuate according to the CYP2C19 phenotype. Although dosages for different phenotypes have been recommended in various retrospective studies, few reports have adjusted the initial VRCZ dose based on CYP2C19 phenotype determined prior to administration. In this study, we prospectively evaluated the usefulness of CYP2C19 polymorphism analysis in adjusting the initial VRCZ maintenance dose. The study enrolled 19 patients who underwent analysis of CYP2C19 polymorphism prior to VRCZ administration. Subjects were classified into 3 phenotype subgroups: extensive metabolizer (EM), intermediate metabolizer (IM), and poor metabolizer (PM). The initial VRCZ maintenance doses given twice daily were proposed as follows: approximately 8, 6, and 4 mg/kg/day for EM, IM and PM, respectively, according to previous reports. In EM, the initial maintenance dose was 8.0 ± 0.5 mg/kg/day, and trough level was 6.6 ± 2.4 μg/mL. By contrast, the initial maintenance doses in IM and PM were 5.5 ± 0.7 and 4.1 ± 0.3 mg/kg/day, and the initial trough concentrations were 2.9 ± 1.2 and 2.6 ± 0.4 μg/mL, respectively. The attainment rate of target trough concentration of 1-6 μg/mL was 50% in EM, and was 100% in IM and PM. Determining the initial dose of VRCZ only by phenotype based on CYP2C19 gene polymorphism was found to be challenging. However, decreasing the initial maintenance dose in IM and PM may be important for adjusting the initial trough level to target range.

Effects of dose and type of corticosteroids on the divergence between estimated glomerular filtration rates derived from cystatin C and creatinine

WHAT IS KNOWN AND OBJECTIVE

Cystatin C (Cys-C) is a useful diagnostic marker for early renal dysfunction, but has the disadvantage of giving false-positive results when corticosteroids are administered. In this study, we aimed to evaluate the dose-dependent effect of corticosteroids on the divergence between estimated glomerular filtration rates based on Cys-C (eGFRcys) and creatinine (eGFRcreat) and calculate the cut-off value of corticosteroid dose having an impact on eGFRcys/eGFRcreat ratio.

METHODS

This retrospective study included 305 patients (1318 therapies) treated with oral or injectable corticosteroids between June 2014 and May 2018, who did not meet the exclusion criteria. All corticosteroid doses were converted to prednisolone equivalent.

RESULTS

Steroid dose correlated significantly with eGFRcys/eGFRcreat ratio for all corticosteroids and for prednisolone (r_s  = -.150 and -.273, respectively), whereas no correlation was observed for methylprednisolone and hydrocortisone. The cut-off value of prednisolone dose for eGFRcys/eGFRcreat ratio < 0.79 was 0.170 mg/kg/day, with 62.4% sensitivity and 84.7% specificity. The correlation coefficient (r_s  = -.434) between prednisolone dose and eGFRcys/eGFRcreat ratio for doses of 0.170 mg/kg/day and higher was markedly larger compared with all corticosteroids.

WHAT IS NEW AND CONCLUSION

These findings suggest that results should be interpreted with caution when using eGFRcys as renal function marker in patients treated with prednisolone at doses of 0.170 mg/kg/day and higher.

Changes in redox state of albumin before and after kidney transplantation in patients with end-stage renal disease

OBJECTIVES

Cardiovascular disease is one of the major causes of death in patients with end-stage kidney disease who have undergone kidney transplantation. Since the complication of cardiovascular disease in patients with chronic kidney disease is strongly linked to oxidative stress, understanding the oxidative stress condition after kidney transplantation would be of great importance for the prevention of cardiovascular disease. This study examined whether improvement of renal function after kidney transplantation has an impact on the redox state of the Cys34 residue of albumin that reflects the level of oxidative stress in blood.

DESIGN & METHODS

We enrolled 23 patients with end-stage renal failure who received kidney transplantation. All patients were followed for 180 days after transplantation. The fractions of albumin isoforms were determined by the electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) method.

RESULTS

Serum creatinine decreased significantly immediately after kidney transplantation, suggesting successful transplantations. The ESI-TOFMS method identified three albumin isoforms cysteinylated at the Cys34 residue (Cys-Cys34-albumin) and the three corresponding albumin isoforms without Cys34 cysteinylation. The fraction of total Cys-Cys34-albumin decreased transiently after kidney transplantation, and was followed by an elevation at day 7 and gradual decrease thereafter until day 180. Meanwhile, reduced albumin concentration did not change until day 14 after kidney transplantation, then showed a significant increase compared to pre-transplant level at day 30 and remained stably elevated until day 180.

CONCLUSIONS

Actual reduced albumin levels were found to exceed pre-transplant levels on or after day 30 following kidney transplantation unlike immediate restoration of renal function. Renal function was recovered immediately following kidney transplantation, but reduced albumen concentration increased above the pre-transplant levels only from day 30 after transplantation.

Venous thromboembolisms and rheology in ovarian cancer patients after postoperative adjuvant paclitaxel and carboplatin therapy

In ovarian cancer patients, chemotherapy can be an independent risk factor for the development of thromboembolic complications, such as venous thromboembolism (VTE). The factors and their values that lead to the development of VTE are remaining unknown in patients undergoing chemotherapy with paclitaxel and carboplatin. This study investigated serial rheological parameters (D-dimer, red blood cell count, hematocrit, and plasma viscosity) for VTE that developed following chemotherapy for ovarian cancer. Forty-eight ovarian cancer patients undergoing chemotherapy were enrolled in this study. A significant difference in the mean values of plasma viscosity and hematocrit was observed between the VTE group (n = 5) and the non-VTE group (n = 43) (P < 0.10). Univariate and multiple regression analyses by stepwise selection identified plasma viscosity as the independent variable associated with VTE development. The VTE incidence was the same as in previous reports. The results support the contention that plasma viscosity could be an index for development of VTE in ovarian cancer after chemotherapy.

P198 Validation of the updated blood pressure classification based on the ACC/AHA guidelines in the perspective of subclinical atherosclerosis in general population

Background

American College of Cardiology (ACC) and American Heart Association (AHA) revised their guideline for hypertension in 2017, and the threshold of normal blood pressure (BP) was lowered, in the perspective of the prevention of optimal prevention of cardiovascular diseases. On the other hand European Society of Cardiology and European Society of Hypertension updated their guideline in 2018. However, the cut off value of blood pressure for hypertension was not changed (sBP ≥ 140 mmHg or dBP ≥ 90 mmHg). Therefore, the validity of the updated guideline of ACC/AHA still remains controversial, and there is so far no evidence regarding the BP category according to the ACC/AHA guidelines in general population.

Purpose

We aimed to clarify the association between the updated BP classification and carotid intima-media thickness (IMT), as a marker of subclinical atherosclerosis, in general population using a community-based cohort.

Methods

We analyzed 1,241 subjects undergoing medical check-ups at the University of Tokyo Hospital. Study subjects were categorized into 3 groups based on their BP levels: normal pressure (sBP &lt; 130 mmHg and dBP &lt; 80 mmHg); stage 1 hypertension (130 mmHg ≤ sBP &lt; 140 mmHg or 80 mmHg ≤ dBP&lt; 90 mmHg); and stage 2 hypertension (sBP ≥ 140 mmHg or dBP ≥ 90 mmHg, including subjects prescribed with antihypertensive agents). We defined carotid plaque as IMT ≥ 1.1 mm.

Results

Out of 1,241 subjects, 556 patients (44.8%) were categorized in the normal BP group, whereas 236 subjects (19.0%) and 449 subjects (36.2%) were categorized in the stage 1 and stage 2 hypertension groups, respectively. Among subjects categorized in the stage 2 hypertension group, 348 subjects (77.5%) patients were taking antihypertensive medications. Percentage of male gender, and age increased with BP category. Classical CVD risk factors such as diabetes mellitus and hypercholesterolemia were common in subjects in the hypertension groups. IMT increased as the BP category progressed from normal BP to stage 2 hypertension. The prevalence of carotid plaque also increased with an increase in BP. Univariate regression analysis showed the linear association between the BP category and prevalence of carotid plaque. Multivariable logistic regression analysis demonstrated that BP category as well as age ≥60 years, male gender, body mass index ≥25 kg/m2, and diabetes mellitus were independently associated with carotid plaque formation. BP category was associated with the prevalence of carotid plaque formation in any subgroup divided by age (&lt; 60 years old, and ≥60 years old) or gender.

Conclusions

Thickening of IMT developed in stage 1 hypertension, and further increased in stage 2 hypertension even in general population, indicating the importance of the therapeutic intervention according to the updated ACC/AHA guideline for hypertension.

Abstract P198 Figure.

Pharmacokinetic and toxicodynamic evaluation of 5-fluorouracil administration after major hepatectomy in a rat model

BACKGROUND

Chemotherapy after hepatectomy for colorectal liver metastasis has not been established, due to the toxic side effects, which are likely related to impaired drug clearance during liver regeneration. We investigated the pharmacokinetic and toxicodynamic evaluation of 5-fluorouracil (5-FU) during liver regeneration after major hepatectomy in a rat model.

METHODS

Thirty-six male Wistar rats were divided into control (C), control with chemotherapy (CC), hepatectomy (H), and hepatectomy with chemotherapy (HC) groups. The CC and HC groups were administered 5-FU for 4 days. Plasma 5-FU, liver weight, and liver dihydropyrimidine dehydrogenase (DPD) were measured. The ileal villous height was measured to determine adverse effects.

RESULTS

The area under the curve and maximum plasma concentration of 5-FU increased by up to 51% and 32%, respectively, in the HC group compared to the CC group. The liver regeneration rate was significantly lower in the HC group than in the H group (67.3 ± 7.4 vs 33.0 ± 5.7%, p < 0.001). The HC group had a significantly lower liver DPD than the CC group (4.4 ± 1.1 mg vs 6.9 ± 1.1 mg, p < 0.01). The HC group had a significantly lower ileal villous height than the CC group (253 ± 40 μm vs. 318 ± 36 μm, p < 0.05).

CONCLUSIONS

Reduction of the total liver DPD following major hepatectomy caused increased plasma 5-FU levels and 5-FU-associated toxicity.

P5293Effect of metabolically health obesity on carotid intima-media thickness in general population: a community-based cohort study

Introduction

Obesity is a common and independent risk factor for all-cause mortality. More specifically, obesity is a major component of atherosclerosis in association with metabolic disorders including metabolic syndrome (MetS), resulting in various cardiovascular diseases (CVD). Alternatively, obese subjects without MetS are prevalent, also referred to as metabolically healthy obesity (MHO). However, most preceding studies regarding MHO have been limited by small cohorts. Therefore, the effect of MHO on atherosclerosis in the general population remains unclear.

Purpose

In this study, we sought to clarify the effect of MHO on carotid intima-media thickness (IMT) as a marker of early stage atherosclerosis using a community-based cohort in general population.

Methods

We examined subjects who underwent medical check-up at our University Hospital. We defined obesity as body mass index ≥25.0 kg/m2. Abdominal obesity, defined as waist circumstance at umbilical level ≥85 cm in men and ≥90 cm in women, was obligatory for the diagnosis of MetS. In addition to abdominal obesity, any two of the following three abnormalities should be observed for the diagnosis of MetS, [1] Dyslipidemia: triglyceride ≥150 mg/dL, HDL-C <40 mg/dL, or use of lipid lowering medication, [2] Hypertension: systolic blood pressure ≥130 mmHg, diastolic blood pressure ≥85 mmHg, or use of antihypertensive medication, and [3] Hyperglycemia: fasting plasma glucose ≥110 mg/dL or use of hypoglycemic medication. MHO was defined as obese subjects without MetS, whereas we defined metabolically unhealthy obesity (MUO) as obese subjects with MetS. We defined carotid plaque as IMT ≥1.1 mm.

Results

Among 1,241 subjects, 857 subjects (69%) were categorized in the normal body weight group, whereas 275 subjects (22%) were categorized as MHO, and 109 subjects (9%) were categorized as MUO. Compared to non-obese subjects, prevalence of classical cardiovascular risk factors including hypertension, diabetes mellitus, and dyslipidemia increased in subjects with MHO, and further increased in those with MUO. IMT was higher in obese subjects compared to those without obesity. Similarly, the prevalence of carotid plaque formation was also higher in obese subjects. Multivariable logistic regression analysis demonstrated that age ≥60 years, male sex, hypertension, diabetes mellitus, MHO subjects (Odds ratio [OR]; 1.6, p=0.005), and MUO subjects (OR 1.7, p=0.04) were independently associated with carotid plaque formation. There was no statistical difference in the risk of carotid plaque formation between subjects with MHO and MUO.

IMT and Carotid Plaque

Conclusions

IMT and the prevalence of carotid plaque are higher in both subjects with MHO and MUO compared to non-obese subjects in the general population. We need to take obesity regardless of the presence of MetS into consideration as high-risk subjects for subsequent CVD.

P4389Effect of cigarette smoking on carotid artery atherosclerosis: a community-based cohort study

Background

Cigarette smoking is closely associated with the development of cardiovascular diseases (CVD), and the European Society of Cardiology/European Atherosclerosis Society (ESC/EAS) guidelines recommend smoking bans.On the other hand, the relationship between cigarette smoking and subclinical atherosclerosis has not been fully studied. Carotid intima-media thickness (cIMT) is commonly used as a subclinical atherosclerosis marker, and a carotid plaque feature is also known to be an important predictor of cardiovascular diseases.

Purpose

We sought to clarify the association between cigarette smoking and subclinical atherosclerosis by evaluating carotid plaque including cIMT and carotid plaque features in general population.

Methods and results

Among 1,209 participants with no prior coronary artery disease who received a medical check-up with cardiovascular examination at our institution, 450 participants (37.2%) were smokers (including both past and current smokers). We defined carotid plaque as cIMT ≥1.1 mm and high-risk plaque as carotid plaque with hypoechoic dominant and/or plaque ulceration. The value of cIMT and the rate of carotid plaque were not different between smokers and never smokers (Figure A & B). However, the rate of carotid high-risk plaque was significantly higher in participants with smokers than those with never smokers (29.7%, vs 23.5%, p=0.011) (Figure C). Even after adjustment with covariates including age, gender and traditional cardiovascular risk factors, cigarette smoking was independently associated with high-risk plaque formation (odds ratio 1.384, 95% CI 1.020–1.877; p=0.037). According to the subgroup analysis classified by age, cigarette smoking was associated with not only the development of high-risk plaque but also the increased value of cIMT in the subgroup over 60 years old, whereas only the rate of high-risk plaque was higher in smokers than never smokers in the subgroup under 60 years old.

Carotid plaque and smoking

Conclusion

The development of high-risk carotid artery plaque may precede thickening of cIMT in cigarette smokers, suggesting that the novel insight for the pathological mechanism underlying cardiovascular events and cigarette smoking.

Successful determination of nilotinib dosage by therapeutic drug monitoring in a patient with chronic myeloid leukemia developing hepatic dysfunction: A case report

Fixed dosage regimen is currently the standard therapy with tyrosine kinase inhibitors (TKI). This case report demonstrates successful determination of nilotinib dosage by therapeutic drug monitoring (TDM) in a patient with chronic myeloid leukemia (CML). TDM may provide useful marker for individualized dosing of TKI for the treatment of CML.

Comparison of performance characteristics between high-performance liquid chromatography and latex agglutination turbidimetric immunoassay for therapeutic drug monitoring of zonisamide

Background

Recently, the Nanopia^® TDM Zonisamide reagent using the latex particle‐enhanced turbidimetric immunoassay (LTIA) method was developed. The aim of this study was to compare the differences in serum zonisamide (ZNS) concentrations quantified by the high‐performance liquid chromatography (HPLC) method and the LTIA method using a TBA‐25FR analyzer.

Methods

A total of 78 samples from 33 patients were quantified by both HPLC and LTIA methods. Deproteinization was used as pretreatment for the HPLC method. The ZNS concentrations quantified by two methods were compared.

Results

The HPLC method had intra‐ and inter‐day precision lower than 1.86% and 9.00%, and accuracy better than 2.44% and 6.33%, respectively. The LTIA method showed intra‐ and inter‐day precision lower than 2.50% and 5.20%, and accuracy better than 15.80% and 10.60%, respectively. The lower limits of quantification for the HPLC and LTIA methods were 1.0 and 5.0 µg/mL, respectively. The ZNS concentration quantified by the HPLC method correlated strongly with that by the LTIA method (r = 0.953, P < 0.001). A Bland‐Altman plot suggested no systematic error between ZNS concentrations quantified by HPLC and LTIA methods.

Conclusion

This study confirmed no differences between the concentrations quantified by the HPLC and LTIA methods at both high and low concentrations, demonstrating the confidence of measurement by the LTIA method.

Progesterone receptor expression in proliferating cancer cells of hormone-receptor-positive breast cancer

Breast cancer has been suggested to have two distinct driving mechanisms: the hormone receptor and the growth factor receptor pathways. We hypothesized that each driving system produces a different expression pattern of estrogen-regulated genes, such as progesterone receptor, in proliferating cells. Progesterone receptor and Ki67 expressions were assessed by dual-fluorescence immunohistochemistry in estrogen-receptor-positive breast cancer tissues. Two distinct proliferating cell populations were observed: progesterone-receptor-positive and progesterone-receptor-negative. In the training cohort, tissues with progesterone-receptor-positive proliferating cells were associated with lower grade and better disease-free survival (p = 0.0055 and 0.0026, respectively). These associations were confirmed in the validation cohort from the neoadjuvant endocrine trial JFMC34 (p = 0.033 and 0.0003, respectively). In the validation cohort, patients with progesterone-receptor-positive proliferating cells responded better to endocrine therapy and had a lower Oncotype DX Recurrence Score. In the multivariate analysis, progesterone receptor status of proliferating cells, but not progesterone receptor or Ki67 alone, was an independent predictor of disease-free survival in both cohorts (p = 0.0043 and 0.0026). In conclusion, the progesterone receptor status of proliferating cancer cells was associated with histological grade and Recurrence Score, and a potent prognostic factor in estrogen-receptor-positive breast cancers. Results suggest that different driving systems generate different expression patterns of progesterone receptor in proliferating cancer cells. Further studies are warranted to validate the findings.

Factors involved in phenoconversion of CYP3A using 4β-hydroxycholesterol in stable kidney transplant recipients

BACKGROUND

Phenoconversion is a phenomenon whereby some genotypic extensive metabolizers transiently exhibit drug metabolizing enzyme activity at similar level as that of poor metabolizers. Renal failure is known to decrease CYP3A activity in humans. Indoxyl sulfate, parathyroid hormone (PTH), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) have been reported to cause CYP3A downregulation in renal failure. We measured plasma concentrations of the above compounds in stable kidney transplant recipients, and evaluated their relations with phenoconversion of CYP3A evaluated by plasma concentration of 4β-hydroxycholesterol, a biomarker of CYP3A activity. Phenoconversion was defined as a genotypic extensive/intermediate metabolizer exhibiting CYP3A activity below the cutoff value that discriminates extensive/intermediate from poor metabolizers.

METHODS

Sixty-three Japanese kidney transplant recipients who underwent transplantation more than 180 days prior to the study were included. Morning blood samples were collected, and CYP3A5 polymorphism as well as plasma concentrations of 4β-hydroxycholesterol, indoxyl sulfate, intact-PTH, IL-6 and TNF-α were determined.

RESULTS

Significantly higher plasma 4β-hydroxycholesterol concentration was observed in recipients with CYP3A5*1 allele (n = 23) compared to those without the allele (n = 40), and the cut-off value was 40.0 ng/mL. Ten recipients with CYP3A5*1 allele exhibited CYP3A activity below 40.0 ng/mL (phenoconversion). Only plasma indoxyl sulfate concentration was significantly higher in recipients with CYP3A phenoconversion compared to those without phenoconversion.

CONCLUSIONS

These findings suggest that higher plasma indoxyl sulfate concentration may be involved in CYP3A phenoconversion. Dose adjustment of drugs metabolized by CYP3A may be needed in patients with CYP3A5*1 allele and high blood indoxyl sulfate.

Development and validation of sensitive and selective quantification of total and free daptomycin in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry

Recently, several studies on pharmacokinetics parameters of daptomycin reported that plasma trough concentration was linked to efficacy and adverse effects, suggesting the usefulness of therapeutic drug monitoring. Although some methods for determining total daptomycin concentration using liquid chromatography coupled to tandem mass spectrometry were established previously, no sensitive quantification method for free drug concentration was established. In this study, we aimed to develop a quantitative method of measuring both total and free daptomycin concentrations using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS), by which both trough and maximum concentrations can be measured. Plasma samples were prepared by solid phase extraction. Free fractions were obtained by ultrafiltration. The assay fulfilled the requirements of US Food and Drug Administration and the European Medicines Agency for assay validation. The methods for total and free drug showed good fit over wide ranges of 0.5-200 and 0.04-40 μg/mL, with lower limits of quantitation of 0.5 and 0.04 μg/mL, respectively. Recovery rate of free daptomycin from ultrafiltration was approximately 100%. Extraction recovery rates of total and free drug measurements ranged from 57.1 to 67.4% and 54.6 to 62.3%, while matrix effect varied between 111.9 and 118.7% and 104.0 and 127.1%, respectively. The maximum and trough concentrations of total and free daptomycin in plasma from two patients in intensive care unit were successfully determined, demonstrating the feasibility of clinical application of the novel methods for determining plasma total and free daptomycin concentrations. In conclusion, we succeeded to develop a sensitive and selective method using UPLC-MS/MS for quantitative measurement of total and free daptomycin concentrations in plasma.

Comparison of whole-blood tacrolimus concentrations measured by different immunoassay systems

INTRODUCTION

Different measured values for tacrolimus were obtained with different automated immunoassays. We aimed to examine the differences in the blood tacrolimus concentrations measured by the major immunoassay systems commercially available in Japan.

METHODS

Whole-blood samples from 118 patients were assayed by 3 commercial assays: chemiluminescent enzyme immunoassay (CLIA), affinity column-mediated immunoassay (ACMIA), and enzyme-multiplied immunoassay technique (EMIT). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for reference.

KEY FINDINGS

The correlation coefficient of immunoassay vs LC-MS/MS was excellent for ACMIA (.83) and CLIA (.81) and good for EMIT (.71). The mean error was negative for ACMIA and positive for CLIA and EMIT. The mean absolute error and root-mean-square error were almost the same for ACMIA and CLIA and lower than those for EMIT.

CONCLUSIONS

The ACMIA and CLIA yield considerably better results than the EMIT for monitoring blood tacrolimus concentrations.

Lactobacillus gasseri PA-3 utilizes the purines GMP and guanosine and decreases their absorption in rats

Excessive intake of purine-rich foods elevates serum uric acid levels, making it a risk factor for hyperuricemia. We hypothesized that lactic acid bacteria ingested with food might utilize purines and contribute to their decreased absorption in the intestines, thereby preventing hyperuricemia. We previously reported that Lactobacillus gasseri PA-3 (PA-3) incorporates adenosine/inosine and related purines and that oral ingestion of PA-3 reduced the absorption of these purines in rats. However, it is unclear whether PA-3 also decreases the absorption of other purines, such as guanosine 5'-monophosphate (GMP) and guanosine. This study investigated whether PA-3 incorporates GMP and guanosine and reduces their absorption in rats. PA-3 incorporated both purines, with ¹⁴C-GMP uptake being greater than that of ¹⁴C-guanosine. Radioactivity in rat blood was significantly lower 30, 45, and 60 minutes after administration of ¹⁴C-GMP plus PA-3 than after administration of ¹⁴C-GMP alone and was significantly lower 15 minutes after administration of ¹⁴C-guanosine plus PA-3 than after administration of ¹⁴C-guanosine alone. PA-3 incorporates GMP and guanosine in vitro. Oral administration of PA-3 with GMP and guanosine reduces the intestinal absorption of these purines in vivo. These findings, together with those of previous studies, indicate that PA-3 reduces the absorption of major purines contained in foods. PA-3 may also attenuate the excessive absorption of dietary purines in humans, protecting these individuals against hyperuricemia.

Pharmacokinetic/Pharmacodynamic Analysis for Doripenem Regimens in Intensive Care Unit Patient

Doripenem (DRPM) is a broad-spectrum antibacterial agent often used as empirical therapy for critically ill patients, although there is a lack of studies validating the recommended dosage regimen for patients admitted to intensive care unit (ICU), based on pharmacokinetic (PK)/pharmacodynamic (PD) index. In this study, we estimated the free time above minimum inhibitory concentration (fT>MIC (%)) of DRPM using population PK analysis of 12 patients in ICU, and evaluated the validity of the dosage regimen stratified by creatinine clearance. Using a 2-compartment population PK model reported previously, the mean total clearance or distribution volume of DRPM estimated by Bayesian estimation was significantly lower or higher than that of based on population PK model. The estimated fT>MIC (%) of the recommended standard (normal renal function: 0.5 g every 8 h, moderate: 0.25 g every 8 h, severe renal impairment: 0.25 g every 12 h) and higher doses (normal: 1.0 g every 8 h, moderate: 0.5 g every 8 h, severe: 0.25 g every 8 h) against MICs of 0.5, 1 and 2 µg/mL exceeded 40% in all patients. When stratified by creatinine clearance, the PK/PD breakpoints estimated by Monte Carlo simulation in three grades of renal function tended to be higher than the previously reported PK/PD breakpoints for patients with urinary tract infection, an infection of lesser severity than ICU patients. These results suggest that the dosage regimen stratified by renal function derived from Japanese package insert may be sufficient to achieve effective treatment in ICU patients.