Comparative Assessment of Tedizolid Pharmacokinetics and Tissue Penetration between Diabetic Patients with Wound Infections and Healthy Volunteers via In Vivo Microdialysis

Penetration of Antibiotics into Subcutaneous and Intramuscular Interstitial Fluid: A Meta-Analysis of Microdialysis Studies in Adults

BACKGROUND AND OBJECTIVE

The interstitial fluid of tissues is the effect site for antibiotics targeting extracellular pathogens. Microdialysis studies investigating these concentrations in muscle and subcutaneous tissue have reported notable variability in tissue penetration. This study aimed to comprehensively summarise the existing data on interstitial fluid penetration in these tissues and to identify potential factors influencing antibiotic distribution.

METHODS

A literature review was conducted, focusing on subcutaneous and intramuscular microdialysis studies of antibiotics in both adult healthy volunteers and patients. Random-effect meta-analyses were used to aggregate effect size estimates of tissue penetration. The primary parameter of interest was the unbound penetration ratio, which represents the ratio of the area under the concentration-time curve in interstitial fluid relative to the area under the concentration-time curve in plasma, using unbound concentrations.

RESULTS

In total, 52 reports were incorporated into this analysis. The unbound antibiotic exposure in the interstitial fluid of healthy volunteers was, on average, 22% lower than in plasma. The unbound penetration ratio values were higher after multiple dosing but did not significantly differ between muscle and subcutaneous tissue. Unbound penetration ratio values were lower for acids and bases compared with neutral antibiotics. Neither the molecular weight nor the logP of the antibiotics accounted for the variations in the unbound penetration ratio. Obesity was associated with lower interstitial fluid penetration. Conditions such as sepsis, tissue inflammation and tissue ischaemia were not significantly associated with altered interstitial fluid penetration.

CONCLUSIONS

This study highlights the variability and generally lower exposure of unbound antibiotics in the subcutaneous and intramuscular interstitial fluid compared with exposure in plasma. Future research should focus on understanding the therapeutic relevance of these differences and identify key covariates that may influence them.

Biomimetic hybrid nanovesicles improve infected diabetic wound via enhanced targeted delivery

Infected diabetic wounds have been raising the global medical burden because of its high occurrence and resulting risk of amputation. Impaired endothelium has been well-documented as one of the most critical reasons for unhealed wounds. Recently, endothelial cell-derived nanovesicles (NVs) were reported to facilitate angiogenesis, whereas their efficacy is limited in infected diabetic wounds because of the complex niche. In this study, extrusion-derived endothelial NVs were manufactured and then hybridized with rhamnolipid liposomes to obtain biomimetic hybrid nanovesicles (HNVs). The HNVs were biocompatible and achieved endothelium-targeted delivery through membrane CXCR4-mediated homologous homing. More importantly, the HNVs exhibited better penetration and antibacterial activity compared with NVs, which further promote the intrinsic endothelium targeting in infected diabetic wounds. Therefore, the present research has established a novel bioactive delivery system-HNV with enhanced targeting, penetration, and antibacterial activity-which might be an encouraging strategy for infected diabetic wound treatment.

Synovial fluid and plasma concentrations of tedizolid in patients with osteoarthritis infected with Staphylococcus aureus effectively determined with fluorescence detection

BACKGROUND

Tedizolid is a new oxazolidinone antibiotic with high potency for the treatment of infections caused by methicillin-resistant Staphylococcus aureus and other species.

CASE PRESENTATION

Two patients with osteoarthritis (women aged 79 and 73 years, cases 1 and 2, respectively) infected with S. aureus were successfully treated with tedizolid after administration of 200 mg once daily via intravenous infusion. The synovial fluid and plasma concentrations of tedizolid during surgery in case 1 at day 7 were 2.1 and 1.6 µg/mL, respectively, yielding a ratio of synovial fluid/plasma of 130%. Those in case 2 at day 2 were 2.9 and 3.3 µg/mL, respectively, corresponding to a ratio of synovial fluid/plasma of 88%.

CONCLUSIONS

These results imply very similar concentrations of tedizolid in the synovial fluid and plasma of osteoarthritis patients with acute S. aureus infection.

Microdialysis as a tool for antibiotic assessment in patients with diabetic foot: a review

Diabetic foot is a serious late complication frequently caused by infection and ischaemia. Both require prompt and aggressive treatment to avoid lower limb amputation. The effectiveness of peripheral arterial disease therapy can be easily verified using triplex ultrasound, ankle-brachial/toe-brachial index examination, or transcutaneous oxygen pressure. However, the success of infection treatment is difficult to establish in patients with diabetic foot. Intravenous systemic antibiotics are recommended for the treatment of infectious complications in patients with moderate or serious stages of infection. Antibiotic therapy should be initiated promptly and aggressively to achieve sufficient serum and peripheral antibiotic concentrations. Antibiotic serum levels are easily evaluated by pharmacokinetic assessment. However, antibiotic concentrations in peripheral tissues, especially in diabetic foot, are not routinely detectable. This review describes microdialysis techniques that have shown promise in determining antibiotic levels in the surroundings of diabetic foot lesions.

Pharmacokinetics and soft-tissue distribution of tebipenem pivoxil hydrobromide using microdialysis: a study in healthy subjects and patients with diabetic foot infections

OBJECTIVE

Tebipenem pivoxil hydrobromide is a novel oral carbapenem prodrug of tebipenem, the active moiety. We assessed tebipenem steady-state pharmacokinetics in the skin and soft tissue in healthy subjects and infected patients with diabetes using in vivo microdialysis.

METHODS

Six healthy subjects and six patients with an ongoing diabetic foot infection (DFI) received tebipenem pivoxil hydrobromide 600 mg orally every 8 h for three doses. A microdialysis probe was inserted in the thigh of healthy subjects or by the wound margin in patients. Plasma and dialysate samples were obtained immediately prior to the third dose and sampled over 8 h.

RESULTS

Tebipenem plasma protein binding (mean ± SD) was 50.2% ± 2.4% in healthy subjects and 53.5% ± 5.6% in infected patients. Mean ± SD tebipenem pharmacokinetic parameters in plasma for healthy subjects and infected patients were: maximum free concentration (fCmax), 3.74 ± 2.35 and 3.40 ± 2.86 mg/L, respectively; half-life, 0.88 ± 0.11 and 2.02 ± 1.32 h; fAUC0-8, 5.61 ± 1.64 and 10.01 ± 4.81 mg·h/L. Tebipenem tissue AUC0-8 was 5.99 ± 3.07 and 8.60 ± 2.88 mg·h/L for healthy subjects and patients, respectively. The interstitial concentration-time profile largely mirrored the free plasma profile within both populations, resulting in a penetration ratio of 107% in healthy subjects and 90% in infected patients.

CONCLUSIONS

Tebipenem demonstrated excellent distribution into skin and soft tissue of healthy subjects and patients with DFI following oral administration of 600 mg of tebipenem pivoxil hydrobromide.

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.

OUP accepted manuscript

Objectives

We assessed the plasma and soft-tissue pharmacokinetic exposure of omadacycline in infected patients with diabetic foot infection (DFI) and healthy volunteers using in vivo microdialysis.

Methods

Eight patients and six healthy volunteers were enrolled and received an omadacycline IV loading dose (200 mg) followed by two oral doses (300 mg) every 24 h. Microdialysis catheters were placed in the soft tissue near the infected diabetic foot wound (patients) or thigh (healthy volunteers). Plasma and dialysate fluid samples were collected, starting immediately prior to the third dose and continued for 24 h post-dose. Protein binding was determined by ultracentrifugation.

Results

The mean ± SD omadacycline pharmacokinetic parameters in plasma for infected patients and healthy volunteers were: C_max, 0.57 ± 0.15 and 1.14 ± 0.26 mg/L; t_½, 16.19 ± 5.06 and 25.34 ± 12.92 h; and total omadacycline AUC_0–24, 6.27 ± 1.38 and 14.06 ± 3.40 mg·h/L, respectively. The omadacycline mean plasma free fraction was 0.21 and 0.20 for patients and healthy volunteers, corresponding to free plasma AUC_0–24 of 1.13 ± 0.37 and 2.78 ± 0.55 mg·h/L, respectively. Omadacycline tissue AUC_0–24 was 0.82 ± 0.38 and 1.37 ± 0.48 mg·h/L for patients and volunteers, respectively.

Conclusions

The present study describes the plasma and soft-tissue exposure of omadacycline in patients with DFI and healthy volunteers. Integrating these data with the microbiological, pharmacokinetic/pharmacodynamic and clinical efficacy data is foundational to support clinical assessments of omadacycline efficacy specifically for DFI. This, coupled with the once-daily oral administration, suggests omadacycline could be an advantageous translational therapy for the hospital and outpatient setting.

Development of a simple method for measuring tedizolid concentration in human serum using HPLC with a fluorescent detector

The objective of the present study was to develop a method to measure tedizolid (TZD) concentration for studying target concentration intervention, pharmacokinetics, and pharmacodynamics of TZD. We established a high-performance liquid chromatography-fluorescence detector assay to measure the TZD concentration in serum for clinical application. Chromatographic separation was carried out on a 5 μm octadecyl silane hypersil column 150 mm × 4.6 mm. The mobile phase consisted of 0.1 M phosphoric acid and methanol (60:40, pH 7.0). Detection was performed at 300 nm and 340 nm for the excitation and emission wavelengths, respectively. The average retention times of TZD and the internal standard were 12.9 and 8.8 min, respectively. High linearity was exhibited over a concentration range of 0.025 to 10.0 μg/mL for TZD (R2 > 0.999). The intra- and inter-assay accuracies of TZD were 99.2% to 107.0% and 99.2% to 107.7%, respectively. The lower limit of quantitation and the lower limit of detection for TZD measurement were 0.025 and 0.01 μg/mL, respectively. The extraction recoveries of TZD were 100.4% to 114.1%.The high-performance liquid chromatography method developed in this study could separate the analytes with a single eluent (isocratic system), within a total run time of 15 min. Both TZD and IS were well separated, without interference from the peaks. Sharp peaks were observed in the chromatograms; problems such as double peaks, shoulder peaks, and broadened peaks were not observed. The proposed method showed acceptable analytical performance and could be used to evaluate serum TZD concentrations in patients.

Antibiotics in Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections (NSTIs) are rare life-threatening bacterial infections characterized by an extensive necrosis of skin and subcutaneous tissues. Initial urgent management of NSTIs relies on broad-spectrum antibiotic therapy, rapid surgical debridement of all infected tissues and, when present, treatment of associated organ failures in the intensive care unit. Antibiotic therapy for NSTI patients faces several challenges and should (1) carry broad-spectrum activity against gram-positive and gram-negative pathogens because of frequent polymicrobial infections, considering extended coverage for multidrug resistance in selected cases. In practice, a broad-spectrum beta-lactam antibiotic (e.g., piperacillin-tazobactam) is the mainstay of empirical therapy; (2) decrease toxin production, typically using a clindamycin combination, mainly in proven or suspected group A streptococcus infections; and (3) achieve the best possible tissue diffusion with regards to impaired regional perfusion, tissue necrosis, and pharmacokinetic and pharmacodynamic alterations. The best duration of antibiotic treatment has not been well established and is generally comprised between 7 and 15 days. This article reviews the currently available knowledge regarding antibiotic use in NSTIs.

Determination of Tedizolid in Bacterial Growth Medium Mueller-Hinton Broth by High-Performance Liquid Chromatography and Its Application to an In Vitro Study in the Hollow-Fiber Infection Model

Pharmacokinetic/pharmacodynamic (PKPD) studies of anti-infectives are frequently performed in in vitro infection models where accurate quantification of antibiotic concentrations in bacterial growth media is crucial to establish PK/PD relationships. Here, a sensitive and rapid high-performance liquid chromatography (HPLC) method was developed to quantify tedizolid (TDZ) in the bacterial growth medium Mueller-Hinton broth (MHB). Matrix components were separated by direct protein precipitation with methanol (1:1). The chromatographic separation was carried out in a Dionex Ultimate 3000 HPLC system using an Accucore® C-18 RPMS HPLC column (2.6 µm, 100 × 2.1 mm) using isocratic elution with 25% acetonitrile and 75% of 0.1% formic acid. The lower limit of quantification was 0.03 mg/L when measured at 300 nm. Following relevant European Medicine Agency guidelines, the method was successfully validated for linearity, selectivity, recovery, inter- and intra-day precision, and accuracy and stability. When applied to in vitro PKPD studies, the method successfully quantified a range of TDZ concentration (Cmin, 0.09-Cmax, 0.65 mg/L) in MHB. The analyzed concentrations were in line with the planned PK profiles. The application of the developed method to quantify TDZ in MHB in in vitro PKPD studies is warranted.

Tedizolid: a service evaluation in a large UK teaching hospital

Tedizolid is a new oxazolidinone antibiotic with little real-life data on use outside of skin and soft tissue infections. There is a paucity of safety evidence in courses greater than 6 days. Our centre uses tedizolid predominantly when linezolid-associated adverse events have occurred. This service evaluation describes our experience to date. We performed a retrospective service evaluation by reviewing case notes, prescription charts, and laboratory system results for each patient prescribed tedizolid at our hospital and recording patient demographics, clinical details, and outcomes. Sixty patients received tedizolid between May 2016 and November 2018. Most were treated for bone or joint infections and had stopped linezolid prior to tedizolid prescription. Mean length of tedizolid therapy was 27 days. Haematological adverse effects were infrequent. Most patients (72%) finished the course and their clinical condition improved during treatment (72%). Adverse events were common, but often not thought to be tedizolid related. Tedizolid appears to be safe in prolonged courses within this context. It may be suitable for longer-term antibiotic therapy within a complex oral and parenteral outpatient antibiotic therapy (COPAT) service. Patients who do not tolerate linezolid can be safely switched to tedizolid if appropriate.

Tedizolid (torezolid) for the treatment of complicated skin and skin structure infections

INTRODUCTION

Acute bacterial skin and skin structure infections (ABSSSI) are among the most frequent infectious diseases. Recently, several new antibiotics with activity against MRSA have been approved. Tedizolid, a second-generation oxazolidinone approved for ABSSSI offers theoretical advantages over first-generation oxazolidinones.

AREAS COVERED

A comprehensive online search of Medline, ClinicalTrials.gov, and conference presentations was made, selecting articles between January 2000 and April 2020. In this review, the authors discuss the chemical and microbiological properties of tedizolid, summarize its efficacy, safety, and potential role in the treatment of ABSSSI as well as the potential for future indications.

EXPERT OPINION

Tedizolid has proven to be non-inferior compared to linezolid for the treatment of ABSSSI in two registrational phase III clinical trials, being well tolerated. Tedizolid exhibits antibacterial activity against the most important ABSSSI pathogens (including multidrug-resistant strains of MRSA), as well as mycobacteria and Nocardia. It appears to have a safe profile, including decreased myelotoxicity and no significant drug interactions. Preliminary studies with longer duration of therapy seem to confirm these potential benefits. Overall, tedizolid expands the newly acquired armamentarium to treat ABSSSI. The role of tedizolid for other indications is under investigation and has yet to be determined.

Determination of free clindamycin, flucloxacillin or tedizolid in plasma: Pay attention to physiological conditions when using ultrafiltration

Pharmacokinetic/pharmacodynamic indices of anti-infective drugs should be referenced to free drug concentrations. In the present study, clindamycin, flucloxacillin and tedizolid have been determined in human plasma by HPLC-UV. The drugs were separated isocratically within 3-6 min on a C₁₈ column using mixtures of phosphate buffer-acetonitrile of pH 7.1-7.2. Sample treatment for the determination of total drug concentrations in plasma included extraction/back-extraction (clindamycin) or protein precipitation (flucloxacillin, tedizolid). The free drug concentrations were determined after ultrafiltration. An ultrafiltration device with a membrane consisting of regenerated cellulose proved to be suitable for all drugs. Maintaining a physiological pH was crucial for clindamycin, whereas maintaining body temperature was essential for tedizolid. The methods were applied to the analysis of total and free drug concentrations in clinical samples and were sufficiently sensitive for pharmacokinetic studies and therapeutic drug monitoring.

Tedizolid phosphate for the treatment of acute bacterial skin and skin-structure infections: an evidence-based review of its place in therapy

Introduction

Tedizolid phosphate is an oxazolidinone approved for the treatment of acute bacterial skin and skin-structure infections (ABSSSIs) and active against methicillin-resistant Staphylococcus aureus.

Aims

The objective of this article was to review the evidence for the efficacy and safety of tedizolid phosphate for the treatment of ABSSSI.

Evidence review

Approval of tedizolid phosphate for the treatment of ABSSSI was based on the results of two phase III randomized controlled trials, ESTABLISH-1 (NCT01170221) and ESTABLISH-2 (NCT01421511), comparing 6-day once-daily tedizolid vs 10-day twice-daily linezolid. In ESTABLISH-1, noninferiority was met with early clinical response rates of 79.5% and 79.4% in tedizolid and linezolid groups, respectively (difference 0.1%, 95% CI –6.1% to 6.2%, with a 10% noninferiority margin). In ESTABLISH-2, noninferiority was met with 85% and 83% rates of early clinical response in tedizolid and linezolid groups, respectively (difference 2.6%, 95% CI –3.0% to 8.2%). Pooled data from ESTABLISH-1 and ESTABLISH-2 indicated a lower frequency of thrombocytopenia in tedizolid-treated than in linezolid-treated patients.

Conclusion

Tedizolid offers the option of an intravenous to oral switch, allows once-daily administration, and presents lower risk of myelotoxicity when a 6-day course is used for the treatment of ABSSSI. Greater economic cost associated with this antibiotic could be offset by its shorter treatment duration and possibility of oral administration in routine clinical practice, although either sponsored or nonsponsored postmarketing observational experience remains essential for ultimately confirming the effectiveness and tolerability of tedizolid outside clinical trials.

Pharmacokinetics of Tedizolid in an Obese Patient after Bariatric Surgery

An obese woman was treated with oral tedizolid 200 mg once daily for pseudoarthrosis 10 years after Roux-en-Y bypass surgery. Total plasma peak concentration was 2.12 mg/liter 3 h after intake, and area under the concentration-time curve from 0 to 24 h (AUC0-24) was 28.3 mg/liter · h. The AUC0-24/MIC ratio for unbound concentrations and for sensitive Staphylococcus and Streptococcus strains was ≥10.8, higher than the target ratio of 3. These results support the use of tedizolid without adjustment after bariatric surgery.