Reduction in Tedizolid Plasma Exposure among End-Stage Renal Disease Patients Undergoing Dialysis Is Explained by Variations in Ideal Body Weight

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.

Importance and Reality of TDM for Antibiotics Not Covered by Insurance in Japan

Under the Japanese health insurance system, medicines undergoing therapeutic drug monitoring (TDM) can be billed for medical fees if they meet the specified requirements. In Japan, TDM of vancomycin, teicoplanin, aminoglycosides, and voriconazole, which are used for the treatment of infectious diseases, is common practice. This means the levels of antibiotics are measured in-house using chromatography or other methods. In some facilities, the blood and/or tissue concentrations of other non-TDM drugs are measured by HPLC and are applied to treatment, which is necessary for personalized medicine. This review describes personalized medicine based on the use of chromatography as a result of the current situation in Japan.

Pharmacokinetics and Pharmacodynamics of Tedizolid

Tedizolid is an oxazolidinone antibiotic with high potency against Gram-positive bacteria and currently prescribed in bacterial skin and skin-structure infections. The aim of the review was to summarize and critically review the key pharmacokinetic and pharmacodynamic aspects of tedizolid. Tedizolid displays linear pharmacokinetics with good tissue penetration. In in vitro susceptibility studies, tedizolid exhibits activity against the majority of Gram-positive bacteria (minimal inhibitory concentration [MIC] of ≤ 0.5 mg/L), is four-fold more potent than linezolid, and has the potential to treat pathogens being less susceptible to linezolid. Area under the unbound concentration–time curve (fAUC) related to MIC (fAUC/MIC) was best correlated with efficacy. In neutropenic mice, fAUC/MIC of ~ 50 and ~ 20 induced bacteriostasis in thigh and pulmonary infection models, respectively, at 24 h. The presence of granulocytes augmented its antibacterial effect. Hence, tedizolid is currently not recommended for immunocompromised patients. Clinical investigations with daily doses of 200 mg for 6 days showed non-inferiority to twice-daily dosing of linezolid 600 mg for 10 days in patients with acute bacterial skin and skin-structure infections. In addition to its use in skin and skin-structure infections, the high pulmonary penetration makes it an attractive option for respiratory infections including Mycobacterium tuberculosis. Resistance against tedizolid is rare yet effective antimicrobial surveillance and defining pharmacokinetic/pharmacodynamic targets for resistance suppression are needed to guide dosing strategies to suppress resistance development.

High-throughput and wide-range simultaneous determination of linezolid, daptomycin and tedizolid in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry

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.

Critical role of tedizolid in the treatment of acute bacterial skin and skin structure infections

Tedizolid phosphate has high activity against the Gram-positive microorganisms mainly involved in acute bacterial skin and skin structure infections, such as strains of Staphylococcus aureus (including methicillin-resistant S. aureus strains and methicillin-sensitive S. aureus strains), Streptococcus pyogenes, Streptococcus agalactiae, the Streptococcus anginosus group, and Enterococcus faecalis, including those with some mechanism of resistance limiting the use of linezolid. The area under the curve for time 0-24 hours/minimum inhibitory concentration (MIC) pharmacodynamic ratio has shown the best correlation with the efficacy of tedizolid, versus the time above MIC ratio and the maximum drug concentration/minimum inhibitory concentration ratio. Administration of this antibiotic for 6 days has shown its noninferiority versus administration of linezolid for 10 days in patients with skin and skin structure infections enrolled in two Phase III studies (ESTABLISH-1 and ESTABLISH-2). Tedizolid's more favorable safety profile and dosage regimen, which allow once-daily administration, versus linezolid, position it as a good therapeutic alternative. However, whether or not the greater economic cost associated with this antibiotic is offset by its shorter treatment duration and possibility of oral administration in routine clinical practice has yet to be clarified.