Mass spectrometry quantitation of immunosuppressive drugs in clinical specimens using online solid-phase extraction and accurate-mass full scan-single ion monitoring.

Introduction: Therapeutic drug monitoring (TDM) of immunosuppressants is essential for optimal care of transplant patients. Immunoassays and liquid chromatography-mass spectrometry (LC-MS) are the most commonly used methods for TDM. However, immunoassays can suffer from interference from heterophile antibodies and structurally similar drugs and metabolites. Additionally, nominal-mass LC-MS assays can be difficult to optimize and are limited in the number of detectable compounds. Objectives: The aim of this study was to implement a mass spectrometry-based test for immunosuppressant TDM using online solid-phase extraction (SPE) and accurate-mass full scan-single ion monitoring (FS-SIM) data acquisition mode. Methods: LC-MS analysis was performed on a TLX-2 multi-channel HPLC with a Q-Exactive Plus mass spectrometer. TurboFlow online SPE was used for sample clean up. The accurate-mass MS was set to positive electrospray ionization mode with FS-SIM for quantitation of tacrolimus, sirolimus, everolimus, and cyclosporine A. MS2 fragmentation pattern was used for compound confirmation. Results: The method was validated in terms of precision, analytical bias, limit of quantitation, linearity, carryover, sample stability, and interference. Quantitation of tacrolimus, sirolimus, everolimus, and cyclosporine A correlated well with results from an independent reference laboratory (r = 0.926-0.984). Conclusions: Accurate-mass FS-SIM can be successfully utilized for immunosuppressant TDM with good correlation with results generated by standard methods. TurboFlow online SPE allows for a simple "protein crash and shoot" sample preparation protocol. Compared to traditional MRM, analyte quantitation by FS-SIM facilitates a streamlined assay optimization process.

Impact of the loss of Laboratory Developed Mass Spectrometry testing at a major academic medical center.

Background: Our laboratory historically performed immunosuppressant and definitive opioid testing in-house as laboratory developed (LDT) mass spectrometry-based tests. However, staffing constraints and supply chain challenges associated with the COVID-19 pandemic forced us to refer this testing to a national reference laboratory. The VALID Act could impose onerous requirements for laboratories to develop LDTs. To explore the potential effect of these additional regulatory hurdles, we used the loss of our own LDT tests to assess the impact on patient care and hospital budgets. Methods: Laboratory information systems data and historical data associated with test costs were used to calculate turnaround times and financial impact. Results: Referral testing has extended the reporting of immunosuppressant results by an average of approximately one day and up to two days at the 95th percentile. We estimate that discontinuing in-house opioid testing has cost our health system over half a million dollars in the year since testing was discontinued. Conclusions: Barriers that discourage laboratories from developing in-house testing, particularly in the absence of FDA-cleared alternatives, can be expected to have a detrimental effect on patient care and hospital finances.

LC-MS/MS method for simultaneous quantification of ten antibiotics in human plasma for routine therapeutic drug monitoring.

Background: Optimizing antimicrobial therapy to attain drug exposure that limits the emergence of resistance, effectively treats the infection, and reduces the risk of side effects is of a particular importance in critically ill patients, in whom normal functions are augmented or/and are infected with pathogens less sensitive to treatment. Achievement of these goals can be enhanced by therapeutic drug monitoring (TDM) for many antibiotics. A liquid chromatography tandem mass spectrometry (LC-MS/MS) method is presented here for simultaneous quantification of ten antimicrobials: cefazolin (CZO), cefepime (CEP), cefotaxime (CTA), ceftazidime (CTZ), ciprofloxacin (CIP), flucloxacillin (FLU), linezolid (LIN), meropenem (MER), piperacillin (PIP) and tazobactam (TAZ) in human plasma. Methods: Plasma samples were precipitated with acetonitrile and injected into the LC-MS/MS. Chromatographic separation was on a Waters Acquity BEH C18 column. Compounds were eluted with water and acetonitrile containing 0.1 % formic acid, using a gradient (0.5-65 % B), in 3.8 min. The flow rate was 0.4 mL/min, and the run time was 5.8 min. Results: The calibration curves were linear across the tested concentration ranges (0.5-250, CZO, CEP, CTA, CTZ and FLU; 0.2-100, MER and TAZ; 0.1-50, CIP and LIN and 1-500 mg/L, PIP). The intra and inter-day imprecision was < 11 %. Accuracy ranged from 95 to 114 %. CTZ and MER showed ionization suppression while CIP showed ionization enhancement, which was normalized with the use of the internal standard. Conclusion: An LC-MS/MS method for simultaneous quantification of ten antimicrobials in human plasma was developed for routine TDM.

Validation of atovaquone plasma levels by liquid chromatography-tandem mass spectrometry for therapeutic drug monitoring in pediatric patients.

Background: Atovaquone has traditionally been used as an antiparasitic and antifungal agent, but recent studies have shown its potential as an anticancer agent. The high variability in atovaquone bioavailability highlights the need for therapeutic drug monitoring, especially in pediatric patients. The goal of our study was to develop and validate the performance of an assay to quantify atovaquone plasma concentrations collected from pediatric cancer patients using LC-MS/MS. Methods: Atovaquone was extracted from a 10 µL volume of K2-EDTA human plasma using a solution consisting of ACN: EtOH: DMF (8:1:1 v:v:v), separated using reverse-phase chromatography, and detected using a SCIEX 5500 QTrap MS system. LC-MS/MS assay performance was evaluated for precision, accuracy, carryover, sensitivity, specificity, linearity, and interferences. Results: Atovaquone and its deuterated internal standard were analyzed using a gradient chromatographic method that had an overall cycle-time of 7.4 min per injection, and retention times of 4.3 min. Atovaquone was measured over a dynamic concentration range of 0.63 - 80 µM with a deviation within ≤ ± 5.1 % of the target value. Intra- and inter-assay precision were ≤ 2.7 % and ≤ 8.4 %, respectively. Dilutional, carryover, and interference studies were also within acceptable limits. Conclusions: Our studies have shown that our LC-MS/MS-based method is both reliable and robust for the quantification of plasma atovaquone concentrations and can be used to determine the effective dose of atovaquone for pediatric patients treated for AML.

Ocrelizumab quantitation by liquid chromatography-tandem mass spectrometry.

Introduction: Ocrelizumab is a monoclonal anti-CD20 antibody approved for the treatment of multiple sclerosis (MS). The clinical value of therapeutic drug monitoring (TDM) for this antibody in treatment of MS is unknown, and an adequately specific and precise quantitation method for ocrelizumab in patient serum could facilitate investigation. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based quantitation methods have been shown to have higher analytic specificity and precision than enzyme-linked immunosorbent assays. Objectives: To establish and validate an LC-MS/MS-based quantitation method for ocrelizumab. Methods: We present an LC-MS/MS-based quantitation method using immunocapture purification followed by trypsinization and analysis by a triple quadrupole mass analyzer obtaining results within the same day. Results: We found that the ocrelizumab peptide GLEWVGAIYPGNGDTSYNQK (Q1/Q3 Quantifier ion: 723.683+/590.77 y112+ Qualifier ion: 723.683+/672.30 y122+) can be used for quantitation and thereby developed a method for quantifying ocrelizumab in human serum with a quantitation range of 1.56 to 200 µg/mL. The method was validated in accordance with EMA requirements in terms of selectivity, carry-over, lower limit of quantitation, calibration curve, accuracy, precision and matrix effect. Ocrelizumab serum concentrations were measured in three MS patients treated with ocrelizumab, immediately before and after ocrelizumab infusion, with additional sampling after 2, 4, 8 and 12 weeks. Measured serum concentrations of ocrelizumab showed expected values for both Cmax and drug half-life over the sampled time period. Conclusion: We have established a reliable quantitation method for serum ocrelizumab that can be applied in clinical studies, facilitating the evaluation of ocrelizumab TDM in MS.

Retrospective analysis of metabolite patterns of clobazam and N-desmethylclobazam in human plasma by LC-MS/MS.

Introduction: Clobazam is a benzodiazepine drug, used to treat Lennox-Gastaut syndrome in patients aged 2 years and older. Objective: To support patient care, our laboratory developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the quantification of clobazam (CLB) and its major active metabolite N-desmethylclobazam (N-CLB) in human plasma or serum samples. Methods: The chromatographic separation was achieved with an Agilent Zorbax Eclipse Plus C-18 RRHD column with mobile phase consisting of 0.05% formic acid in 5 mM ammonium formate, pH 3.0 and 0.1% formic acid in acetonitrile at a flow rate of 600 µL/minute and an injection volume of 5 µL. The detection was performed on a triple quadrupole mass spectrometer in multiple reaction monitoring mode to monitor precursor-to-product ion transitions in positive electrospray ionization mode. Results: The method was validated over a concentration range of 20-2000 ng/mL for CLB and 200-10,000 ng/mL for N-CLB. The lower limit of quantification was 20 ng/mL for CLB and 200 ng/mL for N-CLB with good accuracy and precision. The method performance was successfully evaluated by comparison with two different external laboratories. Retrospective data analysis was performed to evaluate the positivity rate and metabolic patterns for clobazam from our patient population, as a reference laboratory. Among the positive samples, both parent and metabolite were detected in 96.4% of the samples. Conclusion: The method was developed to support therapeutic drug monitoring and the data generated from retrospective analysis could be useful for result interpretation in conjunction with clinical patient information.

Can First-Dose Therapeutic Drug Monitoring Predict the Steady State Area Under the Blood Concentration-Time Curve of Busulfan in Pediatric Patients Undergoing Hematopoietic Stem Cell Transplantation?

Busulfan has high intra-individual variability and possible time-dependent changes in clearance, which complicates therapeutic drug monitoring (TDM), as first dose sampling may not predict the steady state concentrations. In this study, we aimed to use Bayesian pharmacokinetic parameters estimated from the first dose to predict the steady state AUC for busulfan. This observational study was conducted among pediatric patients at King Abdullah Specialist Children's Hospital. From each patient, we collected six blood samples (2, 2.25, 2.5, 3, 4, and 6 h after the start of IV infusion of the first dose). A subset of patients were also sampled at the steady state. First, we modeled the data using only the first dose. The model was used to estimate the empirical Bayesian estimates of clearance for each individual patient, then we used the empirical Bayesian estimates of clearance to predict the AUC0-tau at steady state (i.e., predicted AUC0-tau). Steady state AUC0-tau was also calculated for patients sampled at steady state using the trapezoidal method using raw time concentration data; this was considered the reference AUC0-tau.. Then, we compared the AUC0-tau predicted using the Bayesian approach with the reference AUC0-tau values. We calculated bias and precision to assess predictability. In total we had 33 patients sampled after first dose and at steady state. Using the Bayesian approach to predict the AUC0-tau, bias was -2.8% and precision was 33%. This indicates that first dose concentrations cannot accurately predict steady state busulfan concentrations; therefore, follow-up TDM may be required for optimal dosing.

Therapeutic Drug Monitoring of Anti-Thymocyte Globulin in Allogeneic Stem Cell Transplantation: Proof of Concept.

Anti-thymocyte globulin (ATG), a polyclonal antibody, is used in allogeneic hematopoietic cell transplantation (HCT) to prevent graft-vs.-host-disease (GvHD) and graft failure (GF). Overexposure to ATG leads to poor early T-cell recovery, which is associated with viral infections and poor survival. Patients with severe inflammation are at high risk for GF and GvHD, and may have active infections warranting swift T-cell recovery. As ATG exposure may be critical in these patients, individualized dosing combined with therapeutic drug monitoring (TDM) may improve outcomes. We describe the individualized dosing approach, an optimal sampling scheme, the assay to measure the active fraction of ATG, and the workflow to perform TDM. Using a previously published population pharmacokinetic (PK) model, we determine the dose to reach optimal exposures associated with low GvHD and rejection, and at the same time promote T-cell recovery. Based on an optimal sampling scheme, peak and trough samples are taken during the first 3 days of once-daily dosing. The fraction of ATG able to bind to T-cells (active ATG) is analyzed using a bio-assay in which Jurkat cells are co-cultured with patient's plasma and the binding is quantified using flow cytometry. TDM is performed based on these ATG concentrations on the third day of dosing; subsequent doses can be adjusted based on the expected area under the curve. We show that individualized ATG dosing with TDM is feasible. This approach is unique in the setting of antibody treatment and may result in better immune reconstitution post-HCT and subsequently better survival chances.

Biomarker discovery for personalized therapy selection in inflammatory bowel diseases: Challenges and promises.

The past decades witnessed a significant stride in deciphering the pathophysiology of inflammatory bowel disease, which further advanced drug development adding several new biologicals and small molecules to the arsenal of available therapies. Surprisingly, this wealth in therapeutic options did not yield the aspired high durable response rates. In addition, the increase in therapeutic availabilities ignited an increase in research toward biomarkers that could help assign therapies to patients with the highest probability of response. Luckily, major steps have been undertaken in this domain which resulted in the discovery of some interesting biomarkers that are still under validation. However, the pace in which this domain is progressing, the discordance between short-term endpoints in biomarker discovery studies and the ambition of the disease community in modifying disease course, and the uncertainties about the validity of discovered biomarkers highlight the need for a critical appraisal of research conduct in this domain. In this review, we shed light on areas of improvement in biomarker discovery studies that will help optimize the use of available therapies and break the current therapeutic ceiling.

Therapeutic monitoring of amiodarone and desethylamiodarone after surgical ablation of atrial fibrillation-evaluation of the relationship between clinical effect and the serum concentration.

BACKGROUND: Association between clinical effect and serum concentration of amiodarone (AMI) and its active metabolite desethylamidarone (DEA) in patients after surgical ablation (SA) of atrial fibrillation (AF) has not yet been studied. AIMS: We wanted to find a correlation between AMI and DEA serum concentration and maintaining sinus rhythm (SR) after SA of AF. METHODS: Sixty eight patients with AF who had undergone surgical ablation between 2014 and 2017 were included in a single-centre, prospective, observational study. Maintaining of SR was evaluated by standard 12-lead ECG and 24-hour Holter ECG monitoring at months 1, 3, 6 and 12 following surgery. Therapeutic monitoring of AMI and DEA concentrations was done to optimize therapy and adverse effects were followed up. RESULTS: We have noticed a high success rate in maintaining of SR (overall 83%). The median of serum concentration of AMI was 0.81 mg/L (range 0.16-2.35 mg/L) and DEA 0.70 mg/l (range 0.19-2.63 mg/L). No significant differences were found in the serum concentratration of AMI, DEA or DEA/AMI concentratration ratios between patients with SR and persistent supraventricular tachyarrhythmia except on the second outpatient visit. We observed significant correlation between serum concentration of DEA and thyroid-stimulating hormone elevation. CONCLUSION: We confirmed the efficacy of AMI and DEA at the measured serum concentrations. However, analysis of these concentrations alone cannot replace assessment of the clinical response for treatment. Establishment of individual AMI (and DEA) concentrations at which the optimal therapeutic response is achieved seems to be advantageous. Therapeutic monitoring of AMI and DEA is helpful in personalised pharmacotherapy after SA of AF.

Approach to the diagnosis and treatment of non-tuberculous mycobacterial disease.

Non-tuberculous mycobacteria (NTM) is a collective name given to a group of more than 190 species of Mycobacterium. The clinical presentation for most NTM infections is non-specific, often resulting in delayed diagnosis. Further complicating matters is that NTM organisms can be difficult to isolate. Medications used to treat NTM infection can be difficult for patients to tolerate, and prolonged courses of anti-mycobacterial therapy are often required for adequate suppression or eradication. Herein, we review different NTM syndromes, appropriate diagnostic tests, and treatment regimens.

Relationship Between Patient Sex and Serum Tumor Necrosis Factor Antagonist Drug and Anti-drug Antibody Concentrations in Inflammatory Bowel Disease; A Nationwide Cohort Study.

Background: Anti-drug antibodies to infliximab (ATI) and adalimumab (ATA) are associated with loss of response to tumor necrosis factor antagonist (anti-TNF) therapy in inflammatory bowel disease (IBD). We evaluated the relationship between patient sex and serum TNF antagonist drug and antibody concentrations in inflammatory bowel disease. Methods: A nationwide multicenter retrospective cohort study was conducted by evaluating patients' charts from July 2018 until September 2021. The effect of patient sex on anti-drug antibodies and serum drug concentration in patients with IBD across seven hospitals was investigated. A subgroup analysis also investigated the effect of anti-TNF combination therapy. Geometric means were calculated, and multiple linear regression was used to estimate the adjusted ratio of geometric means (RoGM) and their 95% confidence intervals (CI). Results: In the total study sample (n = 1093), males receiving infliximab had higher anti-drug antibody concentrations (38.3 vs. 22.3 AU/ml; aRoGM = 1.72, 95% CI: 1.30-2.27, p < 0.001) compared to females. Additionally, infliximab serum drug concentrations among males were lower compared to females (2.6 vs. 4.1 ug/ml; aRoGM = 0.62, 95% CI: 0.44-0.88, p = 0.007). In the subgroup analysis (n = 359), male compared to female patients on combination therapy with infliximab and immunomodulators had similar anti-drug antibody concentrations (30.2 vs. 21.9 AU/ml; aRoGM = 1.38, 95% CI: 0.79-2.40, p = 0.254). There was no difference in the anti-drug antibody and serum drug concentrations among males and females on adalimumab. Conclusion: In patients receiving infliximab, anti-drug antibodies were higher in males than females. Consistent with this, serum drug concentrations were lower in males than females on infliximab. There was no difference in anti-drug antibody and serum drug concentrations among males and females on adalimumab. In addition, no difference in anti-drug antibodies between males and females receiving anti-TNF combination therapy was observed.

Linezolid use for the treatment of multidrug-resistant tuberculosis, TB centers of excellence, United States, 2013-2018.

BACKGROUND: In 2019, the World Health Organization released guidelines reflecting major changes in multidrug-resistant tuberculosis (MDR-TB) management-prioritizing fluoroquinolones, bedaquiline, and linezolid (LZD) while de-emphasizing previously favored injectable agents. In some cases, linezolid use is associated with gastrointestinal intolerance, mitochondrial toxicity, and significant drug interactions. CDC's Division of Tuberculosis Elimination supports a network of regional TB Centers of Excellence, which provide medical consultation to healthcare providers. Consultations are documented in a medical consultation database (MCD) enabling evaluation of management questions and recommendations. We describe the scope of clinical inquiries and responses specific to linezolid use for MDR-TB in the US. RESEARCH QUESTION: What are the major themes of provider and patient challenges regarding the use of linezolid for the treatment of MDR-TB in the US? METHODS: We queried MCD consults categorized as "MDR/XDR-TB" from 1/1/2013 to 12/31/2018. Only linezolid-specific consultations were included; incomplete and duplicate entries were excluded as were those citing linezolid historically or theoretically. Subgroup characteristics were assessed (e.g., Center, year, provider type). A descriptive coding scheme was developed through inductive thematic analysis. RESULTS: In 2013-2018 of the 1889 consults regarding MDR/XDR-TB, 934 MDR-TB consults referenced linezolid; 137 met inclusion criteria, representing between 4 and 10% of MDR-TB consults annually. Four main themes emerged: adverse effects (71.5%); concerns about linezolid use due to co-morbidities or concurrent medication use (15.3%); dosing adjustments (8.8%); and monitoring and maintenance logistics (4.4%). INTERPRETATIONS: Linezolid consults consistently exceeded 4% of all consults annually over the 6-year period, suggesting a need for access to expert opinion for providers using linezolid to manage MDR-TB. While only a snapshot of MDR-TB in the US, this evaluation summarizes major provider concerns regarding particular adverse effects, and highlights a need for evidence-based guidance regarding linezolid dosing and toxicity management.

Right Dose, Right Now: Development of AutoKinetics for Real Time Model Informed Precision Antibiotic Dosing Decision Support at the Bedside of Critically Ill Patients.

INTRODUCTION: Antibiotic dosing in critically ill patients is challenging because their pharmacokinetics (PK) are altered and may change rapidly with disease progression. Standard dosing frequently leads to inadequate PK exposure. Therapeutic drug monitoring (TDM) offers a potential solution but requires sampling and PK knowledge, which delays decision support. It is our philosophy that antibiotic dosing support should be directly available at the bedside through deep integration into the electronic health record (EHR) system. Therefore we developed AutoKinetics, a clinical decision support system (CDSS) for real time, model informed precision antibiotic dosing. OBJECTIVE: To provide a detailed description of the design, development, validation, testing, and implementation of AutoKinetics. METHODS: We created a development framework and used workflow analysis to facilitate integration into popular EHR systems. We used a development cycle to iteratively adjust and expand AutoKinetics functionalities. Furthermore, we performed a literature review to select and integrate pharmacokinetic models for five frequently prescribed antibiotics for sepsis. Finally, we tackled regulatory challenges, in particular those related to the Medical Device Regulation under the European regulatory framework. RESULTS: We developed a SQL-based relational database as the backend of AutoKinetics. We developed a data loader to retrieve data in real time. We designed a clinical dosing algorithm to find a dose regimen to maintain antibiotic pharmacokinetic exposure within clinically relevant safety constraints. If needed, a loading dose is calculated to minimize the time until steady state is achieved. Finally, adaptive dosing using Bayesian estimation is applied if plasma levels are available. We implemented support for five extensively used antibiotics following model development, calibration, and validation. We integrated AutoKinetics into two popular EHRs (Metavision, Epic) and developed a user interface that provides textual and visual feedback to the physician. CONCLUSION: We successfully developed a CDSS for real time model informed precision antibiotic dosing at the bedside of the critically ill. This holds great promise for improving sepsis outcome. Therefore, we recently started the Right Dose Right Now multi-center randomized control trial to validate this concept in 420 patients with severe sepsis and septic shock.

An automated mass spectrometric blood test for therapeutic drug monitoring of infliximab.

Infliximab is a monoclonal antibody therapy used to treat several chronic immune-mediated diseases, including Crohn's disease, ulcerative colitis, and rheumatoid arthritis. Infliximab acts by binding to tumor necrosis factor and, thus, inhibiting the inflammatory cascade. While it is a highly effective therapy, a subset of patients on infliximab will develop a loss of response to therapy. In these circumstances, therapeutic drug monitoring of infliximab offers a rational approach to clinical decision making and is associated with improved outcomes. While infliximab has most commonly been measured by immunometric approaches, mass spectrometric approaches offer the opportunity to improve test accuracy and reduce test costs. Herein, we describe a simple, bottom-up high performance liquid chromatography tandem mass spectrometry (LC-MS/MS) approach for quantitation of infliximab in serum. Method development included pre-digestion and digestion experiments to determine critical sample preparation steps, optimization of the workflow and selection of rapidly produced proteolytic peptide(s) for quantitation. The workflow was further improved by automating all sample preparation steps on a robotic liquid handler, facilitating implementation in routine clinical use. A method comparison was performed against a Health Canada and US Food and Drug Administration licensed enzyme-linked immunosorbent assay. Our LC-MS/MS assay accurately reported concentrations based on drug manufacturer targets and demonstrated no interference from endogenous antibodies to infliximab; immunoassay methods did not share these performance characteristics. This LC-MS/MS method provides a workflow amenable to implementation in a clinical laboratory and desired performance characteristics for guiding clinical decision making.

A semi-automated, isotope-dilution high-resolution mass spectrometry assay for therapeutic drug monitoring of antidepressants.

BACKGROUND: Therapeutic drug monitoring (TDM) of antidepressants is important to ensure compliance and to rule out pharmacokinetic abnormalities. Therefore, reliable methods for quantification are important for clinical laboratories. Most of the currently used mass spectrometry methods use triple quadrupoles as mass analyzers. We aimed to develop a method using high-resolution mass spectrometry (HRMS) and wanted to test the suitability of this analyzer for quantitative TDM assays. This would be beneficial since HRMS instruments can also be used for metabolomics and protein analysis and, thus, many different analyses could be run on one instrument. METHODS: After manual protein precipitation of serum samples, further sample clean-up was achieved using a Turbo Flow column preconnected to the analytical LC column. Stable isotope-labelled counterparts of the target analytes were used as internal standards. For detection, we used a Q Exactive Focus Orbitrap mass spectrometer operating in full-scan mode. Ionization was performed in positive ESI. RESULTS: Accuracy, recovery, and matrix effect were acceptable for all analytes. The method demonstrated outstanding precision (within-run imprecision <4.5%, between-run imprecision <7.5%). The selectivity of the method was ensured by chromatographic separation of all isobaric compounds. Close agreement between Orbitrap and triple stage based quantification was observed in a comparison measurement of leftover patient samples. CONCLUSIONS: We have established a selective method for the quantification of antidepressants with outstanding precision using a high-resolution Orbitrap mass spectrometer. The applicability of HRMS instruments to TDM was demonstrated.

Mass spectrometry for therapeutic drug monitoring of anti-tuberculosis drugs.

Therapeutic drug monitoring (TDM) uses drug concentrations, primarily from plasma, to optimize drug dosing. Optimisation of drug dosing may improve treatment outcomes, reduce toxicity and reduce the risk of acquired drug resistance. The aim of this narrative review is to outline and discuss the challenges of developing multi-analyte assays for anti-tuberculosis (TB) drugs using liquid chromatography-tandem mass spectrometry (LC-MS/MS) by reviewing the existing literature in the field. Compared to other analytical methods, LC-MS/MS offers higher sensitivity and selectivity while requiring relatively low sample volumes. Additionally, multi-analyte assays are easier to perform since adequate separation and short run times are possible even when non-selective sample preparation techniques are used. However, challenges still exist, especially when optimizing LC separation techniques for assays that include analytes with differing chemical properties. Here, we have identified seven multi-analyte assays for first-line anti-TB drugs that use various solvents for sample preparation and mobile phase separation. Only two multi-analyte assays for second-line anti-TB drugs were identified (including either nine or 20 analytes), with each using different protein precipitation methods, mobile phases and columns. The 20 analyte assay did not include bedaquiline, delamanid, meropenem or imipenem. For these drugs, other assays with similar methodologies were identified that could be incorporated in the development of a future comprehensive multi-analyte assay. TDM is a powerful methodology for monitoring patient's individual treatments in TB programmes, but its implementation will require different approaches depending on available resources. Since TB is most-prevalent in low- and middle-income countries where resources are scarce, a patient-centred approach using sampling methods other than large volume blood draws, such as dried blood spots or saliva collection, could facilitate its adoption and use. Regardless of the methodology of collection and analysis, it will be critical that laboratory proficiency programmes are in place to ensure adequate quality control. It is our intent that the information contained in this review will contribute to the process of assembling comprehensive multiplexed assays for the dynamic monitoring of anti-TB drug treatment in affected individuals.

Simple and rapid validated HPLC-fluorescence determination of perampanel in the plasma of patients with epilepsy.

We present a simple and fast high-performance liquid chromatography method with fluorescence detection for the determination of the antiepileptic drug perampanel in human plasma. The chromatographic separation was performed on a Kinetex PFP (100 × 2.6 mm, 4.6 µm) column, using a mobile phase of sodium acetate 0.03 M pH 3.7 and acetonitrile (40/60, v/v), at a flow rate of 0.8 mL/min. Total chromatography time for each run was 5 min. Sample preparation (250 µL) involved only one simple precipitation step by acetonitrile spiked with mirtazapine as internal standard. The method was validated over a concentration range of 20-1000 ng/mL and successfully applied to measure perampanel concentrations in plasma samples obtained from patients with epilepsy. This assay combines the high specificity of fluorescence detection with a very simple and fast sample pretreatment and can offer real advantages over existing methods in terms of simplicity and transferability to a therapeutic drug monitoring setting.

Performance evaluation of enzyme immunoassay for voriconazole therapeutic drug monitoring with automated clinical chemistry analyzers.

OBJECTIVE: Voriconazole is a triazole antifungal developed for the treatment of fungal infectious disease, and the clinical utility of its therapeutic drug monitoring has been evaluated. Recently, a new assay for analyzing the serum voriconazole concentration with an automated clinical chemistry analyzer was developed. We evaluated the performance of the new assay based on standardized protocols. METHODS: The analytical performance of the assay was evaluated according to its precision, trueness by recovery, limit of quantitation, linearity, and correlation with results from liquid chromatography-tandem mass spectrometry (LC-MS/MS). The evaluation was performed with the same protocol on two different routine chemistry analyzers. All evaluations were performed according to CLSI Guidelines EP15, EP17, EP6, and EP9 [1-4]. RESULTS: Coefficients of variation for within-run and between-day imprecision were 3.2-5.1% and 1.5-3.0%, respectively, on the two different analyzers for pooled serum samples. The recovery rates were in the range of 95.4-102.2%. The limit of blank was 0.0049 µg/mL, and the limit of detection of the samples was 0.0266-0.0376 µg/mL. The percent recovery at three LoQ levels were 67.9-74.6% for 0.50 µg/mL, 75.5-80.2% for 0.60 µg/mL, and 89.9-96.6% for 0.70 µg/mL. A linear relationship was demonstrated between 0.5 µg/mL and 16.0 µg/mL (R2 =0.9995-0.9998). The assay correlated well with LC-MS/MS results (R2 =0.9739-0.9828). CONCLUSIONS: The assay showed acceptable precision, trueness, linearity, and limit of quantification, and correlated well with LC-MS/MS. Therefore, its analytical performance is satisfactory for monitoring the drug concentration of voriconazole.

A pharmacological profile of ribavirin and monitoring of its plasma concentration in chronic hepatitis C infection.

Chronic hepatitis C (CHC) infection, usually an asymptomatic infection, has long-term serious complications such as cirrhosis, hepatocellular carcinoma, and end-stage liver disease requiring liver transplantation (LT). Several novel drugs against hepatitis C which form part of 'specifically targeted antiviral therapy for hepatitis C' (STAT-C) have been developed. These include NS3/4A protease inhibitors telaprevir, boceprevir, and nucleoside/non-nucleoside polymerase inhibitors (NS5A) which hold promise for future therapy. Despite the development of new anti-hepatitis C virus (HCV) drugs, ribavirin (RBV) remains the single most important drug to prevent relapse and is frequently included among newer regimens being developed with novel small molecule anti-HCV drugs. The current approved treatment is a combination therapy of once weekly subcutaneous pegylated-interferon (PEG-IFN)-α plus body-weight-based oral RBV regimen. The most significant dose-dependent side effect of RBV is hemolytic anemia warranting dose reduction or discontinuation in severe cases compromising sustained virological response (SVR). Monitoring RBV plasma concentration has been challenging due to its peculiar pharmacokinetics and has been done to predict both efficacy and toxicity. Herein, we review the pharmacological profile of RBV and the monitoring of its plasma concentration, monitoring in renal impairment, post-LT, and human immunodeficiency virus (HIV)-HCV co-infection in patients being treated with combination therapy of PEG-IFN-α and RBV.