Population pharmacokinetic analysis of doripenem for Japanese patients in intensive care unit.

We aimed to construct a novel population pharmacokinetics (PPK) model of doripenem (DRPM) for Japanese patients in intensive care unit, incorporating the clearance of DRPM by continuous renal replacement therapy (CRRT). Twenty-one patients treated with DRPM (0.25 or 0.5 g) by intravenous infusion over 1 h were included in the study. Nine of the 21 patients were receiving CRRT. Plasma samples were obtained before and 1, 2, 4, 6 and 8 h after the first DRPM administration. PPK analysis was conducted by nonlinear mixed effects modeling using a two-compartment model. Total clearance (CLtotal) in the model was divided into CRRT clearance (CLCRRT) and body clearance (CLbody). The final model was: CLtotal (L h-1) = CLbody(non-CRRT) = 3.65 × (Ccr/62.25)0.64 in the absence of CRRT, or = CLbody(CRRT) + CLCRRT = 2.49 × (Ccr/52.75)0.42 + CLCRRT in the presence of CRRT; CLCRRT = QE × 0.919 (0.919 represents non-protein binding rate of DRPM); V1 (L) = 10.04; V2 (L) = 8.13; and Q (L h-1) = 3.53. Using this model, CLtotal was lower and the distribution volumes (V1 and V2) tended to be higher compared to previous reports. Also, Ccr was selected as a significant covariate for CLbody. Furthermore, the contribution rate of CLCRRT to CLtotal was 30-40%, suggesting the importance of drug removal by CRRT. The population analysis model used in this study is a useful tool for planning DRPM regimen and administration. Our novel model may contribute greatly to proper use of DRPM in patients requiring intensive care.

Optimal Trough Concentration of Teicoplanin in Febrile Neutropenic Patients with Hematological Malignancy.

BACKGROUND: Teicoplanin is a glycopeptide antibiotic currently used for the treatment of methicillin-resistant Staphylococcus aureus. The need for therapeutic drug monitoring of teicoplanin has been increasingly highlighted as important. It is generally accepted that whereas a plasma trough concentration (Cmin) of ≥10 mg/L is appropriate for the majority of infections, it should exceed 20 mg/L for severe infections. The target Cmin of teicoplanin in patients with febrile neutropenia (FN) has not been reported. The aim of this study was to estimate the target Cmin for the treatment of FN in patients with hematological malignancy. METHODS: In this retrospective, single-center, observational cohort study, the records of 52 hospitalized patients with hematological malignancy who were treated with teicoplanin for FN due to bacteriologically documented or presumptive gram-positive infections were analyzed. RESULTS: A significant difference in the first Cmin of teicoplanin was observed between the response and nonresponse groups in patients with bacteremia. The areas under the receiver operating characteristic curves were 0.80 for clinical efficacy. The cut-off value of teicoplanin Cmin on days 4-6 was 15.2 mg/L (sensitivity 80.0%, specificity 75.0%). CONCLUSIONS: The authors propose a target teicoplanin Cmin of ≥15.2 mg/L for FN in patients with hematological malignancy.

Sensitive and selective quantification of total and free itraconazole and hydroxyitraconazole in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry.

OBJECTIVES: Protein-free (unbound) drug concentrations have been reported to be better biomarker of pharmacodynamics compared with total drug concentrations. In this study, we developed and validated an assay for the quantification of total and free itraconazole and hydroxyitraconazole, a main metabolite with antifungal activity, in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). DESIGN & METHODS: Plasma sample was ultra-filtrated for the measurement of free itraconazole and hydroxyitraconazole concentrations. The samples were prepared by solid phase extraction, and then subject to UPLC-MS/MS quantification. RESULTS: The assay fulfilled the requirements of the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) guidelines for assay validation, with a lower limit of quantification of 10ng/mL for total itraconazole and hydroxyitraconazole, and 0.1 and 0.5ng/mL for free itraconazole and hydroxyitraconazole, respectively. Recovery rates of total itraconazole and hydroxyitraconazole from whole plasma ranged from 53.3% to 64.0%, and recovery rates of free itraconazole and hydroxyitraconazole from ultrafiltrated plasma ranged from 81.6% to 98.7%. Matrix effect varied between 79.1% and 109.4% for total itraconazole and hydroxyitraconazole, and between 81.3% and 99.7% for free itraconazole and hydroxyitraconazole. The assay was successfully applied to therapeutic drug monitoring of itraconazole in three patients with chronic progressive pulmonary aspergillosis or invasive pulmonary aspergillosis. Plasma free hydroxyitraconazole concentrations were 8.1-, 23.3-, and 51.1-fold higher than plasma free itraconazole concentrations in the three patients. CONCLUSIONS: A method for sensitive and selective quantification of plasma total and free itraconazole and hydroxyitraconazole concentrations was developed using UPLC-MS/MS. Free hydroxyitraconazole concentration may be most important in therapeutic drug monitoring of itraconazole.

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.

Pharmacokinetics of ceftriaxone in patients undergoing continuous renal replacement therapy.

BACKGROUND: The duration of time for which the serum levels exceed the minimum inhibitory concentration (MIC) is an important pharmacokinetics (PK)/pharmacodynamics (PD) parameter correlating with efficacy for the antibiotic, ceftriaxone (CTRX). However, no reports exist regarding the PK or PD in patients undergoing continuous renal replacement therapy (CRRT). The purpose of this study was to examine the PK and safety of CTRX in patients undergoing CRRT in order to establish safer and more effective regimens. METHODS: CTRX (1 g once a day) was intravenously administered four or more times to nine patients undergoing CRRT. Blood was collected after administration to measure CTRX concentrations in serum and the filtration fraction of CRRT by high-performance liquid chromatography. In addition to calculating PK parameters from serum CTRX, we (a) estimated by simulation CTRX concentrations when the dose interval was extended to once every 2 or 3 days, (b) calculated CTRX clearance via CRRT from CTRX concentrations in the filtration fraction, and (c) assessed the safety of CTRX use. RESULTS: Total body clearance and the half-life of CTRX were 7.46 mL/min (mean) and 26.5 h, respectively, in patients undergoing CRRT. CTRX was found in the filtration fraction, and the estimated clearance by CRRT was about 70% of total body clearance. Simulations revealed that even when the dose interval is increased to 2 or 3 days, CTRX would retain its efficacy. CONCLUSIONS: Our findings suggest that, depending on the condition of patients undergoing CRRT, CTRX could be used safely against pathogens with a CTRX MIC ≤2 µg/mL, even when extending the dose interval.