Development of a rapid LC-MS/MS method for simultaneous quantification of ten commonly used antibiotic drugs in human serum

The use of TDM in clinical practice to monitor the plasma levels of antibiotics administered to critically ill patients is a well-established approach that allows for optimization of the patient's response to drug therapy, considering the characteristics of the drug, the clinical and physiological status of the patient and any peculiar of the pathogen that caused the clinical picture. In our laboratory, we have developed a single LC-MS/MS analysis for dosing the serum concentration of an antibacterial panel composed of eight antibacterial and two selective inhibitors. The method presented used a certified material furnished by a commercial company and was internally validated using the EMA guidelines. The results have shown high sensitivity, precision, and accuracy, a lower matrix effect combined with simple sample preparation and a time-saving procedure. We have evaluated the recovery rate and matrix effect by testing serum samples without pathological index and serum pools obtained from haemolysed, icteric, or lipemic samples. The assay has shown a recovery range between 94% and 101%.

Simultaneous monitoring of seven antiepileptic drugs by dried blood spot and dried plasma spot sampling: method validation and clinical application of a LC-MS/MS-based technique

Alternative blood sampling strategy can enhance the application of therapeutic drug monitoring (TDM), then improve precision therapy and medication compliance. In developing nations, alternative sampling strategy that allows self-sampling and room temperature transport is especially important. This study validates the use of dried blood spot (DBS) and dried plasma spot (DPS) sampling along with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for analyzing seven common antiepileptic drugs (AEDs) (phenytoin, lamotrigine, levetiracetam, topiramate, carbamazepine, oxcarbazepine and its active metabolite 10,11-dihydro-10-hydroxy carbamazepine) and evaluates their applicability to clinical practice. Following simple protein precipitation with acetonitrile, the AEDs were separated on a C18 column by gradient elution with a mobile phase consisting of acetonitrile-water-0.1% formic acid at a flow rate of 0.65 mL/min. The method provided linear analysis over the tested concentration ranges, with a total run time of 7 min. Intra- and inter-assay precision for all quality controls were ≤12% with accuracies of 85.9%-113%. The average extraction efficiencies were 69.0%-92.4% for DBS and 65.9%-96.5% for DPS, and no significant matrix effects were observed. The AEDs were stable in all samples for seven days at room temprature and 40°C. There was good correlation between the dry and wet plasma concentrations with greater accuracy for DPS compared to DBS indicating that alternative sampling strategy using DBS and DPS are suitable for monitoring the concentrations of AEDs with satisfied performance and logistical advantages.

Effect of Carbamazepine on Darunavir Trough Concentrations: When the Dose Can Make the Difference-A Case Study

BACKGROUND

Carbamazepine (CBZ) is an antiseizure medication known to induce the expression of cytochrome P4503A metabolic enzymes. Here, we describe a man living with HIV who underwent several changes in the daily dose of CBZ, which resulted in different induction effects on darunavir trough concentrations.

METHODS

A 59-year-old man with HIV, successfully undergoing maintenance antiretroviral treatment with darunavir/cobicistat once daily (combined with raltegravir), was prescribed CBZ for recurrent trigeminal neuralgia. Over subsequent months, the patient underwent various changes in the doses (from 200 to 800 mg/d) and trough concentrations (from 3.6 to 18.0 mg/L) of CBZ, guided by clinical response to trigeminal neuralgia.

RESULTS

A highly significant inverse association was observed between darunavir trough concentration and both CBZ dose or trough concentration (coefficient of determination >0.75, P < 0.0001). Ultimately, the darunavir dose was increased to 600 mg twice daily with ritonavir and dolutegravir to ensure optimal antiretroviral coverage, anticipating potential further uptitration of CBZ doses.

CONCLUSIONS

The impact of CBZ on boosted darunavir exposure seemed to be dose- and concentration-dependent. The management of such drug-drug interactions in daily practice was facilitated through therapeutic drug monitoring. This case underscores the importance of a multidisciplinary approach that incorporates both antiretroviral and nonantiretroviral comedications contributing to the optimal management of polypharmacy in individuals living with HIV.

A Validated Assay to Quantify Osimertinib and Its Metabolites, AZ5104 and AZ7550, from Microsampled Dried Blood Spots and Plasma

BACKGROUND

Osimertinib is an oral small-molecule tyrosine kinase receptor inhibitor used to treat non-small cell lung cancer (NSCLC) with a sensitizing epidermal growth factor receptor mutation. Patients may experience drug toxicity and require dose deescalation. The study aimed to quantitate osimertinib and its 2 active metabolites, AZ5104 and AZ7550, in microsampled dried blood spots (DBS) collected from patients with NSCLC using a hemaPEN device and compare them with plasma drug levels.

METHODS

A 6-min ultrahigh-performance liquid chromatography-tandem mass spectrometry method was developed and validated using plasma and DBS. The accuracy, selectivity, matrix effect, recovery, and stability were assessed using bioanalytical validation criteria. The hematocrit effect was investigated in DBS. Drug levels were measured in 15 patients with NSCLC, and the Bland-Altman method was used to compare measurements between plasma and DBS.

RESULTS

The validated assay determined accurate and precise quantities, respectively, for osimertinib in both plasma (93.2%-99.3%; 0.2%-2.3%) and DBS (96.7%-99.6%; 0.5%-10.3%) over a concentration of 1-729 ng/mL. The osimertinib metabolites, AZ5104 and AZ7550, were similarly validated in accordance with bioanalytical guidelines. For 30%-60% patient hematocrit, no hematocrit bias was observed with DBS for all analytes. The Bland-Altman method showed high concordance between plasma and DBS analyte levels. Stability experiments revealed that osimertinib and its metabolites were poorly stable in plasma at room temperature, whereas all analytes were stable in DBS for 10 days at room temperature.

CONCLUSIONS

The measurement of osimertinib, AZ5104, and AZ7550 from hemaPEN microsampled DBS is a convenient and reliable approach for therapeutic drug monitoring that produces measurements consistent with plasma drug levels.

Implementation Strategies Addressing Stakeholder-Perceived Barriers and Enablers to the Establishment of a Beta-Lactam Antibiotic Therapeutic Drug Monitoring Program: A Qualitative Analysis

BACKGROUND

Therapeutic drug monitoring (TDM) of beta-lactam antibiotics (beta-lactams) is increasingly recommended for optimizing antibiotic exposure in intensive care patients with sepsis. However, limited data are available on the implementation of beta-lactam TDM in complex health care settings. Theory-based approaches were used to systematically explore barriers and enablers perceived by key stakeholders in the implementation of beta-lactam TDM in the intensive care unit.

METHODS

In this qualitative descriptive study, the authors interviewed key stakeholders (n = 40): infectious disease physicians, intensive care unit physicians, pharmacists, clinical leaders, scientists, and nurses. The data were thematically analyzed and coded using the theoretical domains framework, and the codes and themes were mapped to the relevant domains of the capability, opportunity, and motivation behavior-change wheel model.

RESULTS

Barriers included a lack of knowledge, experience, evidence, and confidence, which led to concerns about capability, lack of resources, and harm in straying from standard practice. Access to education and guidelines, on-site assays with short turnaround times, communication among teams, and workflow integration were identified as enablers. A focus on patient care, trust in colleagues, and endorsement by hospital leaders were strong motivators. Pharmacist and nursing stakeholder groups emerged as key targets in the implementation of strategies.

CONCLUSIONS

Using theory-based approaches, the authors identified the key barriers and enablers to establishing beta-lactam TDM. These data were used to identify strategies, policies, and key target groups for the implementation of interventions.

Rapid Metabolism Underlying Subtherapeutic Serum Levels of Atypical Antipsychotics Preceding Clozapine Treatment: A Retrospective Analysis of Real-World Data

INTRODUCTION

Adequate antipsychotic treatment intensity is required before diagnosing resistant schizophrenia and initiating clozapine treatment. We aimed to investigate potential rapid drug metabolism underlying low dose-adjusted serum concentration (CD) of non-clozapine atypical antipsychotics preceding clozapine treatment.

METHODS

Patients using non-clozapine, atypical antipsychotics (aripiprazole, risperidone, olanzapine, or quetiapine) within 1 year before starting clozapine were included in this study from a therapeutic drug monitoring service in Oslo, Norway, between 2005 and 2023. Patients were assigned into low CD (LCD) and normal CD (NCD) subgroups. Using a reference sample with 147,964 antipsychotic measurements, LCD was defined as CDs below the 25th percentile, while patients with NCD exhibited CDs between the 25th and 75th percentile of the respective reference measurements. Metabolic ratios, doses, and frequency of subtherapeutic levels of non-clozapine antipsychotics were compared between LCD and NCD groups.

RESULTS

Preceding clozapine treatment, 110 out of 272 included patients (40.4%) were identified with LCD. Compared with the NCD group, LCD patients exhibited higher metabolic ratios of olanzapine (1.5-fold; p < 0.001), quetiapine (3.0-fold; p < 0.001), and risperidone (6.0-fold; p < 0.001). Metabolic ratio differences were independent of smoking and CYP2D6 genotype for olanzapine (p = 0.008) and risperidone (p = 0.016), respectively. Despite higher doses of olanzapine (1.25-fold; p = 0.054) and quetiapine (1.6-fold; p = 0.001) in LCD versus NCD patients, faster metabolism among the former was accompanied by higher frequencies of subtherapeutic levels of olanzapine (3.3-fold; p = 0.044) and quetiapine (1.8-fold; p = 0.005).

CONCLUSION

LCD and associated rapid metabolism of non-clozapine antipsychotics is frequent before starting clozapine treatment. For olanzapine and quetiapine, this is associated with significantly increased risk of having subtherapeutic concentrations.

Dose-dependent effect of lamotrigine on quetiapine serum concentration in patients using instant release tablets

PURPOSE

Lamotrigine was previously reported to reduce serum concentration of quetiapine. The aim of this study was to investigate whether lamotrigine dose or quetiapine formulation was of importance for the drug interaction.

METHODS

Patients combining lamotrigine with quetiapine (cases) were included retrospectively from a routine therapeutic drug monitoring (TDM) service, as were a control group of patients using quetiapine without any interacting drugs. The case and control groups were divided into groups using immediate release (IR) and extended release (XR) quetiapine. The case group was further split into high-dose (> 200 mg/day) and low-dose (≤ 200 mg/day) lamotrigine users. Quetiapine concentration-to-dose (C/D) ratio and metabolite-to-parent ratio (MPR) were compared between the control group and dose-separated case groups using ANOVA test and t-tests.

RESULTS

In total, 406 patients were included. The mean C/D ratio of IR quetiapine was 46% lower in the high-dose lamotrigine group compared with the control group (P < 0.001), while no interaction effect was present in the low dose lamotrigine group (P = 0.7). Regardless of lamotrigine dose, there was no difference in quetiapine C/D ratio for patients using the XR formulation (P = 0.4). The quetiapine MPR was unaffected regardless of formulation and lamotrigine dose (P ≥ 0.06).

CONCLUSION

The effect of lamotrigine in reducing quetiapine concentration is only significant for patients using quetiapine IR tablets who are treated with lamotrigine doses > 200 mg/day. Because of high variability in the interaction effect, TDM of quetiapine should be recommended during co-prescription of high-dose lamotrigine.

Clinical Guidance for Dosing and Monitoring Oral Antihormonal Drugs in Patients with Breast Cancer After Roux-en-Y Gastric Bypass

ABSTRACT

Obesity is associated with an increased risk of cancers, such as breast cancer. Roux-en-Y gastric bypass (RYGB) is a common surgical intervention used to induce weight loss, reduce comorbidities, and improve overall survival. Due to alterations in the gastrointestinal tract, RYGB is associated with changes in oral drug disposition, which can affect treatment outcomes. Oral antihormonal agents were monitored in 9 patients who previously underwent RYGB. The results of therapeutic drug monitoring and estradiol concentrations were analyzed, and a review of the relevant literature was performed. As only 1 of the 6 patients prescribed tamoxifen achieved a therapeutic endoxifen concentration with the standard dose of 20 mg/d, a higher starting dose of 40 mg/d was recommended to increase the probability of attaining a therapeutic plasma concentration. All patients with decreased CYP2D6 metabolic activity could not achieve therapeutic plasma concentrations; therefore, CYP2D6 genotyping was recommended before the initiation of tamoxifen therapy to identify patients who should be switched to aromatase inhibitors. Anastrozole and letrozole exposure in patients who underwent RYGB patients appeared sufficient, with no dose adjustment required. However, until more data become available, monitoring aromatase inhibitor efficacy is recommended. Monitoring the drug concentrations is a viable option; however, only indicative data on therapeutic drug monitoring are available. Therefore, estradiol concentrations should be measured.

Best Practice for Therapeutic Drug Monitoring of Infliximab: Position Statement from the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

BACKGROUND

Infliximab, an anti-tumor necrosis factor monoclonal antibody, has revolutionized the pharmacological management of immune-mediated inflammatory diseases (IMIDs). This position statement critically reviews and examines existing data on therapeutic drug monitoring (TDM) of infliximab in patients with IMIDs. It provides a practical guide on implementing TDM in current clinical practices and outlines priority areas for future research.

METHODS

The endorsing TDM of Biologics and Pharmacometrics Committees of the International Association of TDM and Clinical Toxicology collaborated to create this position statement.

RESULTS

Accumulating data support the evidence for TDM of infliximab in the treatment of inflammatory bowel diseases, with limited investigation in other IMIDs. A universal approach to TDM may not fully realize the benefits of improving therapeutic outcomes. Patients at risk for increased infliximab clearance, particularly with a proactive strategy, stand to gain the most from TDM. Personalized exposure targets based on therapeutic goals, patient phenotype, and infliximab administration route are recommended. Rapid assays and home sampling strategies offer flexibility for point-of-care TDM. Ongoing studies on model-informed precision dosing in inflammatory bowel disease will help assess the additional value of precision dosing software tools. Patient education and empowerment, and electronic health record-integrated TDM solutions will facilitate routine TDM implementation. Although optimization of therapeutic effectiveness is a primary focus, the cost-reducing potential of TDM also merits consideration.

CONCLUSIONS

Successful implementation of TDM for infliximab necessitates interdisciplinary collaboration among clinicians, hospital pharmacists, and (quantitative) clinical pharmacologists to ensure an efficient research trajectory.

Estimated glomerular filtration rate as a tool for early identification of patients with insufficient exposure to beta-lactam antibiotics in intensive care units

BACKGROUND

Only about 50% of intensive care unit (ICU) patients reach a free trough concentration above MIC (100% fT > MIC) of beta-lactam antibiotics. Although dose adjustments based on therapeutic drug monitoring (TDM) could be beneficial, TDM is not widely available. We investigated serum creatinine-based estimated GFR (eGFR) as a rapid screening tool to identify ICU patients at risk of insufficient exposure.

METHOD

Ninety-three adult patients admitted to four ICUs in southeast Sweden treated with piperacillin/tazobactam, meropenem, or cefotaxime were included. Beta-lactam trough concentrations were measured. The concentration target was set to 100% fT > MICECOFF (2, 4, and 16 mg/L based on calculated free levels for meropenem, cefotaxime, and piperacillin, respectively). eGFR was primarily determined via Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) and compared to three other eGFR equations. Data was analysed using logistic regression and receiver operative characteristic (ROC) curves.

RESULTS

With intermittent standard dosing, insufficient exposure was common in patients with a relative eGFR ≥48mL/min/1.73m2 [85%, (45/53)], particularly when treated with cefotaxime [96%, (24/25)]. This eGFR cut-off had a sensitivity of 92% and specificity of 82% (AUC 0.871, p < 0.001) in identifying insufficient exposure. In contrast, patients with eGFR <48mL/min/1.73m2 had high target attainment [90%, (36/40)] with a wide variability in drug exposure. There was no difference between the four eGFR equations (AUC 0.866-0.872, cut-offs 44-51 ml/min/1.73m2).

CONCLUSION

Serum creatinine-based eGFR is a simple and widely available surrogate marker with potential for early identification of ICU patients at risk of insufficient exposure to piperacillin, meropenem, and cefotaxime.

Correlation Between N-Demethyl Imatinib Trough Concentration and Serious Adverse Reactions in Patients with Gastrointestinal Stromal Tumors: A Retrospective Cohort Study

BACKGROUND

Imatinib is the first-line treatment for gastrointestinal stromal tumors; however, the clinical prognosis and adverse reactions of patients vary owing to individualized discrepancies in plasma exposure.

METHODS

To determine the safe interval for steady-state plasma trough concentrations (C min ) of imatinib and its active metabolite, N-demethyl imatinib (NDI), 328 plasma samples from 273 patients treated with imatinib were retrospectively analyzed. Imatinib C min and NDI C min were tested, and adverse reactions were recorded. The association between imatinib C min , NDI C min , and serious adverse reactions was evaluated.

RESULTS

The C min range of imatinib was 209.5-4950.0 ng/mL, with the mean value and SD of 1491.8 ± 731.4 ng/mL. The C min range of NDI was 80.0-2390.0 ng/mL with the mean value and SD of 610.8 ± 281.5 ng/mL. NDI C min was positively correlated with imatinib C min , whereas the ratio of NDI C min to imatinib C min (NDI C min /imatinib C min ) was negatively correlated with imatinib C min . Univariate logistic regression analysis demonstrated that the treatment objective, daily dose, imatinib C min , NDI C min , and imatinib C min + NDI C min were significantly associated with serious adverse reactions. Multivariate logistic regression analysis showed that NDI C min was an independent risk factor for serious adverse reactions, with a threshold of 665 ng/mL.

CONCLUSIONS

NDI C min was an independent risk factor for serious adverse reactions, with a threshold of 665 ng/mL. Monitoring NDI C min was beneficial for the rational application of imatinib and individualized treatment of patients with gastrointestinal stromal tumors.

Fast and Sensitive Analysis of Fosfomycin in Human Plasma Microsamples Using Liquid Chromatography-Tandem Mass Spectrometry for Therapeutic Drug Monitoring

BACKGROUND

Fosfomycin is an antibiotic recently repurposed as a potential combination treatment for difficult-to-treat Gram-negative bacterial infections. The pharmacokinetic features of fosfomycin have demonstrated that different pathophysiologic alterations may affect its exposure. Therapeutic drug monitoring may improve real-time management of fosfomycin therapy in different clinical scenarios.

OBJECTIVES

To develop and validate a fast and sensitive liquid chromatography - tandem mass spectrometry method for measuring fosfomycin in human plasma microsamples (3 µL).

METHODS

Analysis was preceded by a user-friendly pre-analytical single-step process performed via a rapid chromatographic run of 2.5 minutes, followed by negative electrospray ionization and detection on a high-sensitivity triple quadrupole tandem mass spectrometer operated in the multiple reaction monitoring mode. European Medicines Agency guidelines were used to validate the specificity, sensitivity, linearity, precision, accuracy, matrix effects, extraction recovery, limits of quantification, and stability of the analytical method.

RESULTS

The new assay produced accurate (BIAS%: 0.9-9.1) and precise (coefficient of variation [CV]%: 8.1-9.5) measurements of fosfomycin over a concentration range of 1-1000 mg/L. Overall, analyte recovery was consistent (mean values: 91.2%-97.2%) at all tested concentration levels. The analyte was also stable in human plasma and the final extract under various storage conditions. The clinical applicability of the assay was confirmed through quantitation of plasma samples obtained from patients.

CONCLUSIONS

A sensitive liquid chromatography - tandem mass spectrometry method for measuring fosfomycin in plasma was developed and validated according to the European Medicines Agency criteria. Quantitation of fosfomycin in clinical plasma samples confirmed that the assay is suitable for therapeutic drug monitoring in clinical scenarios.

Follow the Area Under the Curve Not the Trough Concentration: A Case Study of Tacrolimus Monitoring in a Kidney Transplant Recipient Cotreated With Phenobarbital

ABSTRACT

The authors described tacrolimus dosing in a kidney transplant patient concurrently treated with phenobarbital, where measuring the tacrolimus area under the curve was necessary to achieve adequate drug exposure and improve kidney function.

Evaluating the Effect of Timing on Point-of-Care Testing of INR

Objectives: To evaluate if there is a difference in International Normalized Ratio (INR) readings taken within the 15 second time frame after lancing the finger vs 30-60 seconds of obtaining a blood drop utilizing a CoaguChek® XS Plus point-of-care (POC) INR machine in patients on warfarin therapy. Methods: All adult patients on anticoagulation therapy with warfarin who were managed in a pharmacist-run anticoagulation clinic were considered for inclusion in the study. The mean difference of INR readings taken less than 15 seconds vs between 30-60 seconds after the blood drop was obtained from the finger was assessed. Results: A total of 62 pairs of INR results were included in the study. There was a mean difference in INR of .076 (95% CI 0.011-.140; P = .0217) when comparing INR readings taken less than 15 seconds and between 30-60 seconds after the blood drop was obtained from the finger. Conclusions: There was a significant difference in INR readings taken less than 15 seconds vs 30-60 seconds after obtaining the blood drop when utilizing a POC INR machine. INR readings taken 30-60 seconds after obtaining a blood drop with the CoaguChek® XS Plus POC INR machine is not acceptable for use to monitor patients on warfarin.

A Randomized Trial Comparing Standard of Care to Bayesian Warfarin Dose Individualization

The quality of warfarin treatment may be improved if management is guided by the use of models based upon pharmacokinetic-pharmacodynamic theory. A prospective, two-armed, single-blind, randomized controlled trial compared management aided by a web-based dose calculator (NextDose) with standard clinical care. Participants were 240 adults receiving warfarin therapy following cardiac surgery, followed up until the first outpatient appointment at least 3 months after warfarin initiation. We compared the percentage of time spent in the international normalized ratio acceptable range (%TIR) during the first 28 days following warfarin initiation, and %TIR and count of bleeding events over the entire follow-up period. Two hundred thirty-four participants were followed up to day 28 (NextDose: 116 and standard of care: 118), and 228 participants (114 per arm) were followed up to the final study visit. Median %TIR tended to be higher for participants receiving NextDose guided warfarin management during the first 28 days (63 vs. 56%, P = 0.13) and over the entire follow-up period (74 vs. 71%, P = 0.04). The hazard of clinically relevant minor bleeding events was lower for participants in the NextDose arm (hazard ratio: 0.21, P = 0.041). In NextDose, there were 89.3% of proposed doses accepted by prescribers. NextDose guided dose management in cardiac surgery patients requiring warfarin was associated with an increase in %TIR across the full follow-up period and fewer hemorrhagic events. A theory-based, pharmacologically guided approach facilitates higher quality warfarin anticoagulation. An important practical benefit is a reduced requirement for clinical experience of warfarin management.

Tocilizumab Dose Tapering Based on a Model-Based Algorithm is Feasible in Clinical Practice: A Short Communication

BACKGROUND

Tocilizumab in the treatment of rheumatoid arthritis (RA) is a potential candidate for concentration-guided tapering because the standard dose of tocilizumab results in a wide range of serum concentrations, usually above the presumed therapeutic window, and an exposure-response relationship has been described. However, no clinical trials have been published to date on this subject. Therefore, the objective of this study was to assess the feasibility of the tapering of intravenous (iv) tocilizumab with the use of a pharmacokinetic model-based algorithm in RA patients.

METHODS

A randomized controlled trial with a double-blind design and follow-up of 24 weeks was conducted. RA patients who received the standard of tocilizumab for at least the past 24 weeks, which is 8 mg/kg every 4 weeks, were included. Patients with a tocilizumab serum concentration above 5 mg/L at trough were randomized between concentration-guided dose tapering, referred to as therapeutic drug monitoring (TDM), or the standard 8 mg/kg dose. In the TDM group, the tocilizumab dose was tapered with a recently published model-based algorithm to achieve a target concentration of 4-6 mg/L after 20 weeks of dose tapering.

RESULTS

Twelve RA patients were included and 10 were randomized between the TDM and standard dose group. The study was feasible regarding the predefined feasibility criteria and patients had a positive attitude toward therapeutic drug monitoring. In the TDM group, the tocilizumab trough concentration within patients decreased on average by 24.5 ± 18.3 mg/L compared with a decrease of 2.8 ± 12 mg/L in the standard dose group. None of the patients in the TDM group reached the drug range of 4-6 mg/L. Instead, tocilizumab concentrations of 1.6 and 1.5 mg/L were found for the 2 patients who completed follow-up on the tapered dose. No differences in RA disease activity were observed between the 2 study groups.

CONCLUSIONS

This study was the first to show that it is feasible to apply a dose-reduction algorithm based on a pharmacokinetic model in clinical practice. However, the current algorithm needs to be optimized before it can be applied on a larger scale.

Fingerprick volumetric absorptive microsampling for therapeutic drug monitoring of antiseizure medications: Reliability and real-life feasibility in epilepsy patients

Volumetric absorptive microsampling (VAMS) is increasingly proposed as a clinically reliable therapeutic drug monitoring (TDM) sampling methodology. The study aimed to establish the reliability and real-life feasibility of patient self-collected capillary VAMS for TDM of antiseizure medication (ASMs), using plasma ASMs concentrations from venous blood as a reference standard. Nurses collected venous and capillary blood samples using VAMS. Afterward, persons with epilepsy (PWE) performed VAMS sampling by themselves. All samples were analyzed by UHPLC-MS/MS. We performed a cross-validation study, comparing ASMs concentrations obtained by VAMS nurses and patients' self-collected versus plasma through Bland-Altman analysis and Passing-Bablok regression. We enrolled 301 PWE (M: F 42.5%:57.5%; mean age 44±16 years), treated with 13 ASMs, providing a total of 464 measurements. Statistical analysis comparing VAMS self-collected versus plasma ASMs concentrations showed a bias close to zero and slope and intercept values indicating a good agreement for CBZ, LCS, LEV, LTG, OXC, PB, and PHT, while a systematic difference between the two methods was found for VPA, PMP, TPM and ZNS. This is the first study showing the reliability and feasibility of the real-world application of PWE self-collected VAMS for most of the ASMs considered, giving a promising basis for at-home VAMS applications.

Influence of ultrafiltration conditions on the measurement of unbound drug concentrations: flucloxacillin as an example

BACKGROUND

When performing therapeutic drug monitoring (TDM) for flucloxacillin, it is advised to measure the unbound, not the total, flucloxacillin concentration. To be able to accurately quantify unbound flucloxacillin concentrations, a reliable analytical method is indispensable.

OBJECTIVE

To determine the influence of temperature and pH of the sample during ultrafiltration on the measured unbound fraction of flucloxacillin.

MATERIALS AND METHODS

We performed three different experiments. In a single laboratory experiment, we investigated the influence of ultrafiltration temperature (10°C, room temperature and 37°C) on the measured unbound fraction of flucloxacillin for three concentration levels. In a multiple laboratory experiment, the results of eight laboratories participating in an international quality control programme measuring unbound flucloxacillin concentrations were analysed. In the third experiment, patient samples were ultrafiltrated using four different conditions: (i) physiological pH and room temperature; (ii) unadjusted pH (pH 9 after freezing) and room temperature; (iii) physiological pH and 37°C and (iv) unadjusted pH and 37°C.

RESULTS

For all experiments, measurement of samples that were ultrafiltrated at room temperature resulted in a substantially lower unbound fraction compared to samples that were ultrafiltrated at 37°C. Adjusting the pH to physiological pH only had a minimal impact on the measured unbound fraction.

CONCLUSIONS

On the basis of these findings and considering the need for fast, simple and reproducible sample pretreatment for TDM purposes, we conclude that ultrafiltration of flucloxacillin should be performed at physiological temperature (37°C), but adjustment of pH does not seem to be necessary.

Effect of Extraction Procedure Substitution on Automated Tacrolimus, Sirolimus, and Cyclosporine Assays

BACKGROUND

An erroneously high tacrolimus level was reported to a clinician. A root cause analysis investigation failed to determine the cause of the error. It was suspected that the incorrect preanalytical extraction reagent and procedure was used during testing; however, how this would affect the assayed drug concentration was unclear. Here we investigated the effect of the substitution of sirolimus, tacrolimus, and cyclosporine extraction reagents on assayed drug concentration.

METHODS

Tacrolimus, sirolimus, and cyclosporine concentration were measured on the Abbott Architect i2000 analyzer. Each assay requires a preanalytical extraction step, with a distinct reagent. We investigated the effect of the substitution of the extraction reagents and procedure between the 3 assays on the measured drug concentration. Two experiments were performed, one on samples of known drug concentration and one on samples with no drug present.

RESULTS

Substituting cyclosporine and sirolimus extraction procedures increased assayed tacrolimus concentrations from 5.6 to 8.47 (+51.25%) and 8.13 (+45.18%) ng/mL, respectively. Extraction procedure substitutions decreased assayed sirolimus from 13.63 to 4.60 (-66.25%) and 8.07 (-40.79%) ng/mL for cyclosporine and tacrolimus. Cyclosporine concentration increased from 274.60 to 391.30 (+42.50%) ng/mL using sirolimus extraction reagents and to 757.30 (+175.78%) ng/mL using tacrolimus extraction reagents. Cross-reactivity was observed between the tacrolimus assay and sirolimus and cyclosporine extraction reagents.

CONCLUSIONS

Significant changes, both positive and negative, are observed in assayed drug concentration when incorrect extraction procedures are used in the Abbott i2000 tacrolimus, sirolimus, and cyclosporine assays. Preanalytic extraction procedures should be investigated when performing root cause analysis for erroneous therapeutic drug values.

Evaluation of Busulfan as a Third-Party Immunoassay on a Clinical Chemistry Analyzer

BACKGROUND

Busulfan is widely used in conditioning regimens to prepare patients for hematopoietic stem cell transplantation. Therapeutic drug monitoring (TDM) is critical due to large inter- and intra-individual variability in busulfan pharmacokinetics, and the risk of adverse consequences of toxicity including hepatic veno-occlusive disease. Busulfan is most commonly measured by liquid chromatography-mass spectrometry (LC-MS/MS), which is not as widely available in clinical laboratories as automated routine clinical chemistry analyzers. The objective was to perform analytical verification of a busulfan immunoassay on the Abbott Alinity c platform.

METHODS

The MyCare Oncology busulfan immunoassay was configured as a third-party reagent on the Abbott Alinity c. Imprecision, linearity, sample carryover, and onboard stability of reagent studies were evaluated. The performance of the busulfan immunoassay using the Abbott Alinity c was compared to the Beckman Coulter AU480 using sodium heparinized plasma, as well as to LC-MS/MS using lithium heparinized plasma.

RESULTS

The imprecision goal of 8% was met, and linearity within the analytical measurement range of 240 to 1700 ng/mL was verified. Sample carryover was negligible, and the reagents were stable onboard for at least 84 days. The busulfan immunoassay correlated well with LC-MS/MS (slope = 0.949, y-intercept = -7.8 ng/mL, r2 = 0.9935) and the Beckman Coulter AU480 (slope = 1.090, y-intercept = -34.5 ng/mL, r2 = 0.9988).

CONCLUSIONS

This study demonstrated successful analytical verification of a busulfan third-party immunoassay on the Abbott Alinity c platform. The ability to perform TDM of busulfan on a routine clinical chemistry analyzer will positively impact turnaround times to improve patient outcomes.

Stability and Analytical Characterization of Voriconazole as Measured by Immunoassay

BACKGROUND

Voriconazole is a broad-spectrum triazole antifungal agent recommended for invasive fungal diseases, including invasive aspergillosis. Therapeutic drug monitoring via voriconazole target trough concentration is important to ensure efficacy while preventing toxicity. Our aim was to determine the stability of voriconazole as adapted and measured by an immunoassay.

METHODS

Plasma from patient samples (n = 45) evaluated by a liquid chromatography with tandem mass spectrometry (LC-MS/MS) method was compared against an ARK immunoassay method, adapted and optimized on the Abbott Alinity c analyzer. Stability of voriconazole and analytical performance of ARK immunoassay was assessed, including functional sensitivity, limit of blank (LoB), limit of detection (LoD), and limit of quantification (LoQ), linearity, and precision.

RESULTS

ARK voriconazole immunoassay was highly correlated (Pearson R = 0.988) to the LC-MS/MS method, with an average bias of 0.09 mg/L (2%). CV at LoQ of 0.5 mg/L was 3.7% while the functional sensitivity was established at 0.05 mg/L. Overall imprecision with liquid quality control material obtained from ARK was 5.0%, 6.3%, and 5.9% at 1 mg/L, 5 mg/L, and 10 mg/L, respectively. Limit of blank and LoD were 0.02 mg/L and 0.05 mg/L, respectively. Voriconazole in lithium heparin plasma separator tube declines over time, with a decrease that is more evident near or above toxic concentrations.

CONCLUSION

Voriconazole collected in gel separation tubes declines over time, possibly due to absorptive properties. Voriconazole measurements by immunoassay and LC-MS/MS demonstrated acceptable comparability with sufficient level of sensitivity and precision.

Is there a role for the laboratory monitoring in the management of specific antidotes of direct oral anticoagulants?

Given the growing number of patients receiving direct oral anticoagulant (DOAC), patients requiring rapid neutralization is also increasing in case of major bleedings or urgent surgery/procedures. Idarucizumab is commercialized as a specific antidote to dabigatran while andexanet alfa has gained the Food and Drug Administration and the European Medicines Agency approval as an oral anti-factor Xa inhibitors antidote. Other antidotes or hemostatic agents are still under preclinical or clinical development, the most advanced being ciraparantag. DOAC plasma levels measurement allows to appropriately select patient for antidote administration and may prevent unnecessary prescription of expensive molecules in some acute clinical settings. However, these tests might be inconclusive after some antidote administration, namely andexanet alfa and ciraparantag. The benefit of laboratory monitoring following DOAC reversal remains unclear. Here, we sought to provide an overview of the key studies evaluating the safety and efficacy of DOAC reversal using the most developed/commercialized specific antidotes, to discuss the potential role of the laboratory monitoring in the management of patients receiving DOAC specific antidotes and to highlight the areas that deserve further investigations in order to establish the exact role of laboratory monitoring in the appropriate management of DOAC specific antidotes.

Development of an on-site therapeutic drug monitoring method using a portable spectrometer

We report on the development of an on-site therapeutic drug monitoring (TDM) method for vancomycin (VCM) utilizing a portable spectrometer and commercially available immunoturbidimetric assay reagents designed for automated clinical chemistry analyzers. The method enables the quantification of VCM in plasma samples within 10 min, with a good correlation between the measured values and the theoretical values (r2 = 0.995). The intra and inter-day precisions were found to be below 12.5% and 17.7%, respectively. Moreover, we established a correlation between the quantitative values using this method and those measured through HPLC-UV and automated clinical chemistry analyzers, showing good reliability (R2 = 0.970 and 0.951, respectively). This method allows anyone to rapidly perform TDM at the bedside and is expected to be used to evaluate appropriate drug therapy.

Eculizumab dose tapering should take into account the nonlinearity of its pharmacokinetics

AIMS

Eculizumab is a monoclonal antibody targeting complement protein C5 used in renal diseases. As recommended dosing regimen leads to unnecessarily high concentrations in some patients, tailored dosing therapeutic drug monitoring was proposed to reduce treatment cost. The objectives of the present work were (i) to investigate the target-mediated elimination of eculizumab and (ii) whether a pharmacokinetic model integrating a nonlinear elimination allows a better prediction of eculizumab concentrations than a linear model.

METHODS

We analysed 377 eculizumab serum concentrations from 44 patients treated for atypical haemolytic uraemic syndrome and C3 glomerulopathy with a population pharmacokinetic approach. Critical concentrations (below which a non-log-linear decline of concentration over time is evidenced) were computed to estimate the relevance of the target-mediated elimination. Simulations of dosing regimens were then performed to predict probabilities of target attainment (i.e. trough >100 mg/L).

RESULTS

Pharmacokinetics of eculizumab was nonlinear and followed a mixture of first-order (CL = 1.318 mL/day/kg) and Michaelis-Menten elimination (Vmax = 26.07 mg/day, Km = 24.06 mg/L). Volume of distribution (72.39 mL/kg) and clearance were weight-dependent. Critical concentrations (Vmax/CL) ranged from 144.7 to 759.7 mg/L and were inversely related to body weight (P = .013). Nonlinearity was thus noticeable at therapeutic concentrations. Simulations predicted that 1200 mg of eculizumab every 21 days would allow 85% and 76% of patients to maintain a therapeutic exposure, for 50 or 90 kg body weight, respectively.

CONCLUSIONS

Our study investigates the nonlinear elimination of eculizumab and discusses the importance of accounting for eculizumab target-mediated elimination in therapeutic drug monitoring.

Development of a therapeutic drug-monitoring algorithm for outpatients receiving voriconazole: A multicentre retrospective study

AIMS

Although therapeutic drug monitoring (TDM) of voriconazole is performed in outpatients to prevent treatment failure and toxicity, whether TDM should be performed in all or only selected patients remains controversial. This study evaluated the association between voriconazole trough concentrations and clinical events.

METHODS

We investigated the aggravation of clinical symptoms, incidence of hepatotoxicity and visual disturbances, change in co-medications and interaction between voriconazole and co-medications in outpatients receiving voriconazole between 2017 and 2021 in three facilities. Abnormal trough concentrations were defined as <1.0 mg/L (low group) and >4.0 mg/L (high group).

RESULTS

A total of 141 outpatients (578 concentration measurements) met the inclusion criteria (treatment, 37 patients, 131 values; prophylaxis, 104 patients, 447 values). The percentages of patients with abnormal concentrations were 29.0% and 31.5% in the treatment and prophylaxis groups, respectively. Abnormal concentrations showed 50% of the concentrations at the first measurement in both therapies. Aggravation of clinical symptoms was most frequently observed in the low treatment group (18.2%). Adverse events were most common in the high group for both therapies (treatment, hepatotoxicity 6.3%, visual disturbance 18.8%; prophylaxis, hepatotoxicity 27.9%). No differences were found in changes to co-medications and drug interactions. In the prophylaxis group, prescription duration in the presence of clinical events tended to be longer than in their absence (47.4 ± 23.4 days vs 39.7 ± 21.9 days, P = .1132).

CONCLUSIONS

We developed an algorithm based on clinical events for appropriate implementation of TDM in outpatients. However, future interventions based on this algorithm should be validated.

Plasma chitotriosidase enzyme activity as a novel therapeutic monitor for cysteamine treatment in nephropathic cystinosis: A retrospective validation study

BACKGROUND

Cystine-depleting therapy in nephropathic cystinosis is currently monitored via the white blood cell cystine assay, although its application and usefulness are limited by practical and technical issues. Therefore, alternative biomarkers that are widely available, more economical and less technically demanding, while reliably reflecting long-term adherence to cysteamine treatment, are desirable. Recently, we proposed chitotriosidase enzyme activity as a potential novel biomarker for the therapeutic monitoring of cysteamine treatment in cystinosis. In this study, we aimed to validate our previous findings and to confirm the value of chitotriosidase in the management of cystinosis therapy.

MATERIALS & METHODS

A retrospective study was conducted on 12 patients treated at the National Institutes of Health Clinical Center and followed up for at least 2 years. Plasma chitotriosidase enzyme activity was correlated with corresponding clinical and biochemical data.

RESULTS

Plasma chitotriosidase enzyme activity significantly correlated with WBC cystine levels, cysteamine total daily dosage and a Composite compliance score. Moreover, plasma chitotriosidase was a significant independent predictor for WBC cystine levels, and cut-off values were established in both non-kidney transplanted and kidney transplanted cystinosis patients to distinguish patients with a good versus poor compliance with cysteamine treatment. Our observations are consistent with those of our previous study and validate our findings.

CONCLUSIONS

Chitotriosidase enzyme activity is a valid potential alternative biomarker for monitoring cysteamine treatment in nephropathic cystinosis patients.

SYNOPSIS

Chitotriosidase enzyme activity is a valid potential alternative biomarker for monitoring cysteamine treatment in nephropathic cystinosis patients.

Therapeutic drug monitoring in pregnancy: Levetiracetam

OBJECTIVE

Levetiracetam (LEV) is an antiseizure medication that is mainly excreted by the kidneys. Due to its low teratogenic risk, LEV is frequently prescribed for women with epilepsy (WWE). Physiological changes during gestation affect the pharmacokinetic characteristics of LEV. The goal of our study was to characterize the changes in LEV clearance during pregnancy and the postpartum period, to better plan an LEV dosing paradigm for pregnant women.

METHODS

This retrospective observational study incorporated a cohort of women who were followed up at the epilepsy in pregnancy clinic at Tel Aviv Sourasky Medical Center during the years 2020-2023. Individualized target concentrations of LEV and an empirical postpartum taper were used for seizure control and to reduce toxicity likelihood. Patient visits took place every 1-2 months and included a review of medication dosage, trough LEV blood levels, week of gestation and LEV dose at the time of level measurement, and seizure diaries. Total LEV concentration/dose was calculated based on LEV levels and dose as an estimation of LEV clearance.

RESULTS

A total of 263 samples were collected from 38 pregnant patients. We observed a decrease in LEV concentration/dose (C/D) as the pregnancy progressed, followed by an abrupt postpartum increase. Compared to the 3rd trimester, the most significant C/D decrease was observed at the 1st trimester (slope = .85), with no significant change in the 2nd trimester (slope = .11). A significant increase in C/D occurred postpartum (slope = 5.23). LEV dose was gradually increased by 75% during pregnancy compared to preconception. Average serum levels (μg/mL) decreased during pregnancy. During the postpartum period, serum levels increased, whereas the LEV dose was decreased by 24%, compared to the 3rd trimester.

SIGNIFICANCE

LEV serum level monitoring is essential for WWE prior to and during pregnancy as well as postpartum. Our data contribute to determining a rational treatment and dosing paradigm for LEV use during both pregnancy and the postpartum period.

Bioanalytical technologies using temperature-responsive polymers

In recent decades, various bioanalytical technologies have been investigated for appropriate medical treatment and effective therapy. Temperature-responsive chromatography is a promising bioanalytical technology owing to its functional properties. Temperature-responsive chromatography uses a poly(N-isopropylacrylamide)(PNIPAAm) modified stationary phase as the column packing material. The hydrophobic interactions between PNIPAAm and the analyte could be modulated by changing the column temperature because of the temperature-responsive hydrophobicity of PNIPAAm. Thus, the chromatography system does not require organic solvents in the mobile phase, making it suitable for therapeutic drug monitoring in medical settings such as hospitals. This review summarizes recent developments in temperature-responsive chromatography systems for therapeutic drug monitoring applications. In addition, separation methods for antibody drugs using PNIPAAm are also summarized because these methods apply to the therapeutic drug monitoring of biopharmaceutics. The temperature-responsive chromatography systems can also be utilized for clinical diagnosis, as they can assess multiple medicines simultaneously. This highlights the significant potential of temperature-responsive chromatography in medicine and healthcare.

Microsampling Techniques Suitable for Therapeutic Drug Monitoring of Antipsychotics

BACKGROUND

Therapeutic drug monitoring (TDM) of antipsychotics for dose titration or detection of noncompliance is not uncommon in daily practice. Normally, TDM implies measuring a drug concentration in venous blood samples. This technique is invasive and requires trained assistants and patients normally need to go to an outpatient clinic. Over the past decades, sensitivity of analytical equipment has improved leading to a growing interest in microsampling techniques. These techniques are minimally invasive, require a small volume (<100 μL), usually result in stable samples, and can be collected by the patient or a caregiver at home. Before a microsampling technique can be used in daily routine, proper method development and a clinical validation study should be performed.

METHOD

For this review, the databases of PubMed and Embase were systematically searched. Currently available microsampling techniques for antipsychotics in blood, serum, or plasma are summarized. Subsequently, it has also been assessed whether these techniques are sufficiently validated for TDM monitoring in daily practice.

RESULTS

Several microsampling techniques are available today, for example, dried blood spot sampling, dried plasma extraction cards, and volumetric absorptive microsampling. Eighteen studies were identified in which a microsampling technique for 1 or a few antipsychotics was chemically analytically and clinically validated. However, the majority of these studies have relevant shortcomings that mean its usefulness for different antipsychotics is not yet well established.

CONCLUSIONS

Microsampling for TDM can be recommended for patients using clozapine. For TDM of other antipsychotics, it is a very promising development.

Determination of Aminophylline in Human Serum Using Hydrogel Microspheres for Coupled Surface-Enhanced Raman Spectroscopy (SERS) and Solid-Phase Extraction

Aminophylline (AMP) is a bronchodilator. The therapeutic and toxic doses are very close. Therefore, therapeutic drug monitoring (TDM) of AMP is essential in clinical practice. Microgels were synthesized by free radical precipitation polymerization. Silver@poly(N-isopropyl acrylamide) (Ag@PNIPAM) hybrid microgels were obtained by loading silver (Ag) nanoparticles into the three-dimensional network of the microgels by in situ reduction. The microgel is a three-dimensional reticular structure with tunable pore size, large specific surface area, and good biocompatibility, which can be used as a sorbent for solid-phase extraction (SPE) of target molecules in complex matrices and as a surface-enhanced Raman spectroscopy (SERS) substrate. We optimized the conditions affecting SERS enhancement, such as silver nitrate (AgNO3) concentration and SPE time, according to the SERS strategy of Ag@PNIPAM hybrid microgels to achieve label-free TDM for trace AMP in human serum. The results showed good linearity between the logarithmic concentration of AMP and its SERS intensity in the range of 1-1.1 × 102 µg/mL, with a correlation coefficient (R2) of 0.9947 and a low detection limit of 0.61 µg/mL. The assay accuracy was demonstrated by spiking experiments, with recoveries ranging from 93.0 to 101.8%. The method is rapid, sensitive, reproducible, requires simple sample pretreatment, and has good potential for use in clinical treatment drug monitoring.

Towards clinical adherence monitoring of oral endocrine breast cancer therapies by LC-HRMS-method development, validation, comparison of four sample matrices, and proof of concept

Oral endocrine therapies (OET) for breast cancer treatment need to be taken over a long period of time and are associated with considerable side effects. Therefore, adherence to OET is an important issue and of high clinical significance for breast cancer patients' caregivers. We hypothesized that a new bioanalytical strategy based on liquid chromatography and high-resolution mass spectrometry might be suitable for unbiased adherence monitoring (AM) of OET. Four different biomatrices (plasma, urine, finger prick blood by volumetric absorptive microsampling (VAMS), oral fluid (OF)) were evaluated regarding their suitability for AM of the OET abemaciclib, anastrozole, exemestane, letrozole, palbociclib, ribociclib, tamoxifen, and endoxifen. An analytical method was developed and validated according to international recommendations. The analytical procedures were successfully validated in all sample matrices for most analytes, even meeting requirements for therapeutic drug monitoring. Chromatographic separation of analytes was achieved in less than 10 min and limits of quantification ranged from 1 to 1000 ng/mL. The analysis of 25 matching patient samples showed that AM of OET is possible using all four matrices with the exception of, e.g., letrozole and exemestane in OF. We were able to show that unbiased bioanalytical AM of OET was possible using different biomatrices with distinct restrictions. Sample collection of VAMS was difficult in most cases due to circulatory restraints and peripheral neuropathy in fingers and OF sampling was hampered by dry mouth syndrome in some cases. Although parent compounds could be detected in most of the urine samples, metabolites should be included when analyzing urine or OF. Plasma is currently the most suitable matrix due to available reference concentrations.

The Effect of Polymorphisms and Other Biomarkers on Infliximab Exposure in Paediatric Inflammatory Bowel Disease: Development of a Population Pharmacokinetic Model

BACKGROUND

Therapeutic drug monitoring (TDM) of infliximab has been shown to be a effective strategy for inflammatory bowel disease (IBD). Population pharmacokinetic (PopPK) modeling can predict trough concentrations for individualized dosing.

OBJECTIVE

The aim of this study was to develop a PopPK model of infliximab in a paediatric population with IBD, assessing the effect of single nucleotide polymorphisms (SNPs) and other biomarkers on infliximab clearance.

METHODS

This observational and ambispective single-centre study was conducted in paediatric patients with IBD treated with infliximab between July 2016 and July 2022 in the Paediatric Gastroenterology Service of the Hospital Universitari Vall d'Hebron (HUVH) (Spain). Demographic, clinical, and analytical variables were collected. Twenty SNPs potentially associated with variations in the response to infliximab plasma concentrations were analysed. infliximab serum concentrations and antibodies to infliximab (ATI) were determined by ELISA. PopPK modelling was performed using nonlinear mixed-effects analysis (NONMEM).

RESULTS

Thirty patients (21 males) were included. The median age (range) at the start of infliximab treatment was 13 years (16 months to 16 years). A total of 190 samples were obtained for model development (49 [25.8%] during the induction phase). The pharmacokinetics (PK) of infliximab were described using a two-compartment model. Weight, erythrocyte sedimentation rate (ESR), faecal calprotectin (FC), and the SNP rs1048610 (ADAM17) showed statistical significance for clearance (CL), and albumin for inter-compartmental clearance (Q). Estimates of CL1 (genotype 1-AA), CL2 (genotype 2-AG), CL3 (genotype 3-GG), Q, Vc, and Vp (central and peripheral distribution volumes) were 0.0066 L/h/46.4 kg, 0.0055 L/h/46.4 kg, 0.0081 L/h/46.4 kg, 0.0029 L/h/46.4 kg, 0.6750 L/46.4 kg, and 1.19 L/46.4 kg, respectively. The interindividual variability (IIV) estimates for clearance, Vc, and Vp were 19.33, 16.42, and 36.02%, respectively.

CONCLUSIONS

A popPK model utilising weight, albumin, FC, ESR, and the SNP rs1048610 accurately predicted infliximab trough concentrations in children with IBD.

A validated method for simultaneous quantification of four antiretrovirals in dried blood spot and plasma using LC-MS/MS: Application to efavirenz therapeutic drug monitoring in pregnant patients

INTRODUCTION

The specific physiological background induced by pregnancy leads to significant changes in maternal pharmacokinetics, suggesting potential variability in plasma concentrations of antiretrovirals. Pregnant HIV patients exposed to subtherapeutic doses, particularly in the last trimester of the pregnancy, have higher chances to transmit the infection to their children. Therefore, the therapeutic drug monitoring of antiretrovirals in HIV pregnant patients would be of great value.

OBJECTIVES

This study aimed to develop and validate a sensitive liquid chromatograph tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of efavirenz, raltegravir, atazanavir, and ritonavir in dried blood spots (DBS) and plasma.

DESIGN AND METHODS

The analytes were extracted from the DBS punch and plasma with a mixture of methanol:zinc sulfate 200 mM (50:50, v/v) and 100 % methanol, respectively. For the chromatographic separation a Shim-pack® C18, 4.6 mm × 150 mm, 5 μm column was used. Detection was performed in a 3200-QTRAP® mass spectrometer, with a run time of 6 min.

RESULTS

The assay was linear in the range of 15-1,000 ng/mL for raltegravir, 50-10,000 ng/mL for both atazanavir and ritonavir, 50-5,000 ng/mL for efavirenz. Precision and accuracy at these concentrations were less than 15 % for all analytes. Raltegravir, atazanavir, and ritonavir were stable for seven days at 23 °C and 40 °C, whereas efavirenz was stable for twenty-four hours at the same conditions.

CONCLUSIONS

The method was successfully applied to quantify efavirenz in DBS samples obtained from HIV-1 infected pregnant volunteers under antiretroviral therapy. The concentrations of efavirenz in DBS and plasma were comparable according to Passing-Bablok regression and Bland-Altman analysis.

Existing and Emerging Technologies for Therapeutic Monitoring of Lithium: A Scoping Review

BACKGROUND/PURPOSE

Lithium is an effective psychoactive drug. It has a narrow therapeutic margin, with subtherapeutic levels or intoxication commonly occurring. Therapeutic drug monitoring (TDM) of lithium has several barriers. This scoping review aims to describe and analyze existing and emerging technologies for lithium TDM and to describe the lithium quantification parameters (precision, accuracy, detection limit) attributed to each technology.

METHOD

PubMed, Scopus, Web of Science, and Google Scholar were searched. Studies that described lithium quantification and complied with PRISMA-ScR guidelines were included. Articles selection was conducted by 2 researchers. Good precision was defined if its relative standard deviation <3%; acceptable, from 3% to 5%; and low, >5%. Accuracy was considered good if the error <5%; acceptable, 5%1 to 0%; and low if it was >10%.

RESULTS

Of the 2008 articles found, 22 met the inclusion criteria. Of these, 14 studies concerned laboratory devices, in which precision was found to be low in one third of cases, and half had good precision. Accuracy of one third was good, another third was low, and the remaining third did not report accuracy. The other 8 studies concerned portable devices, in which precision was low in more than 60% of the cases and good in 25% of the studies. Accuracy was low in 50% of the cases, and good in just over a third. Limits of detection included the therapeutic range of lithium in all studies.

CONCLUSIONS

Among emerging technologies for lithium TDM, precision and accuracy remain a challenge, particularly for portable devices.

Modified application of SAMe-TT2R2 scoring system in Asian patients with atrial fibrillation for the selection of oral anticoagulants

BACKGROUND/AIMS

The SAMe-TT2R2 score is used for assessing anticoagulation control (AC) quality with warfarin. However, it is hard to apply SAMe-TT2R2 score in Asian patients with atrial fibrillation (AF), because it has not been proven in those populations. This study aimed to validate the SAMe-TT2R2 score in Asian patients with AF and suggest a modified SAMe- TT2R2 score for this population.

METHODS

We analyzed 710 Korean patients with AF who were using warfarin. The AC quality was assessed as the mean time in therapeutic range (TTR). Each component of SAMe-TT2R2 score was evaluated for the relationship with AC. Further clinical factors that predict AC were analyzed. Identified factors were re-assorted and constructed as SA2Me-TTR scoring system.

RESULTS

Of the components of the SAMe-TT2R2 score, female, age, and rhythm control were associated with AC. Heart failure and renal insufficiency were newly identified factors associated with AC. The modified SA2Me-TTR score was reconstructed with the relevant risk factors (S, female gender, 1 point; A, age < 60 yr, 2 points; Me, medical history of heart failure, 1 point; T, treatment for rhythm control, 1 point; T, history of stroke or transient ischemic attack, 1 point; R, renal insufficiency, 1 point). The modified SA2Me-TTR score demonstrated an excellent relationship with the grading of AC. The modified SA2Me-TTR score ≤ 1 identified patients with good AC (hazard ratio 2.46, 95% CI 1.75-3.47).

CONCLUSION

The modified SA2Me-TTR score was useful for guiding oral anticoagulants selection in Asian patients with AF.

Managing Risks with Newer Oral Small Molecules in Patients with Inflammatory Bowel Diseases

PURPOSE OF REVIEW

Treatment of Inflammatory Bowel Diseases (IBD) is challenging; thus, the need for newer therapeutic options with an oral route of administration has led to the development of novel small molecules drugs (SMDs). We aim to highlight the most common Adverse events (AEs) associated with SMDs and recommendations on monitoring for AEs before and during treatment.

RECENT FINDINGS

SMDs, such as Tofacitinib, a JAK inhibitor, have been associated with laboratory abnormalities, infections, and risk of thromboembolic events. Therefore, oral agents with greater selectivity in JAK inhibition, such as tofacitinib and upadacitinib, were later developed. Ozanimod and etrasimod, S1PR agonists, require closer safety profile monitoring by clinicians. Multiple therapies have been recently developed with variable efficacy. However, they have been associated with AEs, and some require close monitoring prior to and during therapy. Clinicians should highlight these adverse events to patients while reassuring the safety profile of these novel SMDs for IBD is favorable.

Influence of rheumatoid factor on serum drug levels of TNF inhibitors with different structures in rheumatoid arthritis

OBJECTIVES

Certolizumab pegol (CZP), an Fc-free antibody fragment, has shown stable serum levels and steady efficacy in the treatment of RA patients, irrespective of RF levels at baseline. Here, we examine, in clinical practice, the effect of baseline RF and ACPA levels on serum drug levels of IFX, ADL and CZP an Fc-free antibody fragment.

METHODS

This is a retrospective study performed in real-world patients. We assessed 170 patients with RA: 90 (53%) received IFX, 48 (28%) ADL and 32 (19%) CZP. Demographic and clinical variables, RF and ACPA levels were obtained at the baseline visit (T0), and patients were stratified based on negative, low, medium, or high levels. After 6 months (T6) serum drug levels and anti-drug antibodies (ADAb), were computed.

RESULTS

While CZP serum levels did not differ across RF groups at T6, high baseline RF was linked to lower serum drug levels compared to RF negative status in treatment with complete monoclonal antibodies IFX and ADL. No differences in disease activity measured by DAS28 at baseline were observed across RF quartiles in patients treated with IFX or ADL. ADAb was observed in 26 patients with IFX, 3 with ADL and 1 with CZP, following 6 months of treatment. Patients with high baseline RF levels dropped out more frequently by secondary non-response in IFX or ADL than CZP (80% vs. 75% vs. 33%, p=0.002).

CONCLUSIONS

In this real word data evaluation, CZP serum levels were independent of RF levels in patients however patients with high baseline RF levels who obtained IFX or ADL had lower serum drug levels at 6 months than baseline RF-negative patients. In addition, secondary non-response was more frequent in patients with high RF levels treated with IFX and ADL.

Can Slow Personalized Titration Using C-Reactive Protein Monitoring Decrease the High Rates and Mortality of Clozapine-Associated Myocarditis Seen in Some Countries? A Call for Research

PURPOSE/BACKGROUND

The hypothesis that slower personalized titration may prevent clozapine-associated myocarditis and decrease the disproportion incidence of 3% found in Australia was not described in a recent Australian article in this journal.

METHODS

Six countries in addition to Australia have published information suggesting a similar incidence of clozapine-associated myocarditis. On September 19, 2023, PubMed searches were updated for articles from the United States, Korea, Japan, Canada, New Zealand, and Turkey.

FINDINGS/RESULTS

An incidence of 3.5% (4/76) was found in a US hospital, but US experts were the first to propose that clozapine-associated myocarditis may be a hypersensitivity reaction associated with rapid titration and possibly preventable. Koreans and Japanese are of Asian ancestry and need lower minimum therapeutic doses for clozapine than patients of European ancestry. A 0.1% (2/1408) incidence of myocarditis during clozapine titration was found in a Korean hospital, but pneumonia incidence was 3.7% (52/1408). In 7 Japanese hospitals, 34% (37/110) of cases of clozapine-associated inflammation were found during faster titrations (based on the official Japanese titration) versus 13% (17/131) during slower titrations (based on the international titration guideline for average Asian patients). Recent limited studies from Canada, New Zealand, and Turkey suggest that slower personalized titration considering ancestry may help prevent clozapine-associated myocarditis.

IMPLICATIONS/CONCLUSIONS

Other countries have very limited published data on clozapine-associated myocarditis. Based on a recent Australian case series and these non-Australian studies, the author proposes that Australia (and other countries) should use slow personalized titration for clozapine based on ancestry and c-reactive protein monitoring.

Capecitabine-induced severe adverse events-therapeutic drug monitoring and DPYD-gene analysis are recommended

In this report, two cases of patients with severe adverse events after an adjuvant treatment with capecitabine are described in detail. The first patient suffered from a severe ileocolitis, where ultimately intensive care treatment, total colectomy and ileum resection was necessary. The second patient experienced a toxic enteritis, which could be managed conservatively. Post-therapeutic DPYD genotyping was negative in the former and positive in the latter case. Patients can be categorised in normal, moderate and poor DPYD metabolisers to predict the risk of adverse events of capecitabine treatment. Guidelines in various European countries recommend pretherapeutic DPYD genotyping, whereas it is not recommended by the National Comprehensive Cancer Network in the USA. Irrespective of DPYD genotyping, strict therapeutic drug monitoring is highly recommended to reduce the incidence and severity of adverse events.

Preoperative Drug Monitoring in Management of Patients with Hip Fracture on Treatment with Direct Oral Anticoagulants

Purpose

Aim of the present study was to evaluate whether monitoring direct oral anticoagulant (DOAC) levels may improve management of anticoagulated patients who need surgery for hip fracture.

Patients and Methods

A total of 147 out of 2231 (7.7%) patients with hip fracture admitted to a tertiary teaching hospital were on DOACs (group A), whereas 206 patients matched for age, sex, and type of fracture not on anticoagulant or P2Y12 platelet inhibitors were considered as control group (group B). Patients on DOACs were divided into two subgroups: A1 in which intervention was scheduled in relation to the last drug intake according to current guidelines, and A2 included patients in whom time of surgery (TTS) was defined according to DOAC levels. Neuraxial anesthesia was considered with DOAC levels <30 ng/mL, general anesthesia for levels in the range 30-50 ng/mL.

Results and conclusions

TTS was significantly lower in controls than in DOAC patients: surgery within 48 hours was performed in 80.6% of group B versus 51% in group A (p<0.0001). In A2, 41 patients underwent surgery within 48 hours (56%) in comparison to 32 A1 patients (45.1%; p=0.03). TTS and length of hospitalization were on average 1 day lower in patients with assay of DOAC levels. Finally, 35/39 (89%) patients with DOAC levels <50 ng/mL had surgery within 48 hours (26 under neuraxial anesthesia, without any neurological complication, and 13 in general anesthesia).

Conclusion

DOAC assay in patients with hip fracture may be useful for correct definition of time to surgery, particularly in patients who are candidates for neuraxial anesthesia. Two-thirds of patients with DOAC levels <50 ng/mL at 48 hours from last drug intake underwent uneventful neuraxial anesthesia, saving at least 24 hours in comparison to guidelines.

Dose adjustment strategy of levetiracetam in pregnant patients with epilepsy: Case report and literature review

RATIONALE

Pregnant patients with epilepsy are prone to preterm delivery, stillbirth, or cesarean section, and their mortality rate is almost 10 times higher than that of normal pregnant women. The potential negative influences of antiepileptic drugs (AEDs) on the fetus are weighed against the necessity for achieving optimal control of seizures. Treatment with AEDs during pregnancy is a major challenge for pregnant women and healthcare teams.

PATIENT CONCERNS

This paper reports two cases of young women diagnosed with pregnancy and epilepsy.

INTERVENTION

The dose of levetiracetam was adjusted under the guidance of therapeutic drug monitoring to reduce the effects of seizures on the fetus and the incidence of reproductive toxicity caused by adverse drug reactions.

OUTCOMES

Epilepsy was well controlled in the two pregnant patients, and the newborns had no genetic disorders.

LESSONS

It is recommended to regularly monitor the serum LEV level in pregnant patients with epilepsy. This practice serves as a foundation for adjusting the drug treatment plan and offering more precise guidance for medication management during pregnancy.

Comparison of pharmacokinetics software for therapeutic drug monitoring of piperacillin in patients with severe infections

OBJECTIVE

To evaluate the predictive performance of population pharmacokinetic models for piperacillin (PIP) available in the software MwPharm, TDMx and ID-ODs for initial dosing selection and therapeutic drug monitoring (TDM) purposes.

METHODS

This is a prospective observational study in adult patients with severe infections receiving PIP treatment. Plasma concentrations were quantified by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. The differences between predicted and observed PIP concentrations were evaluated with Bland-Altman plots; additionally, the relative and absolute bias and precision of the models were determined.

RESULTS

A total of 145 PIP plasma concentrations from 42 patients were analysed. For population prediction, MwPharm showed the best predictive performance with a mean relative difference of 34.68% (95% CI -197% to 266%) and a root mean square error (RMSE) of 60.42 µg/mL; meanwhile TDMx and ID-ODs under-predicted PIP concentrations. For individual prediction, the TDMx model was found to be the most precise with a mean relative difference of 7.61% (95% CI -57.63 to 72.86%), and RMSE of 17.86 µg/mL.

CONCLUSION

Current software for TDM is a valuable tool, but it may also include different population pharmacokinetic models in patients with severe infections, and should be evaluated before performing a model-based TDM in clinical practice. Considering the heterogeneous characteristics of patients with severe infections, this study demonstrates the need for therapy personalisation for PIP to improve pharmacokinetic/pharmacodynamic target attainment.

Meropenem population pharmacokinetics and model-based dosing optimisation in patients with serious bacterial infection

OBJECTIVES

The objective of this study was to develop a population pharmacokinetic model of meropenem in a heterogeneous population of patients with a serious bacterial infection in order to propose dosing optimisation leading to improved achievement of the pharmacokinetic/pharmacodynamic (PK/PD) target.

METHODS

A total of 174 meropenem serum levels obtained from 144 patients during therapeutic drug monitoring were analysed using a non-linear mixed-effects modelling approach and Monte Carlo simulation was then used to compare various dosing regimens in order to optimise PK/PD target attainment.

RESULTS

The meropenem volume of distribution of the patient population was 54.95 L, while clearance started at 3.27 L/hour and increased by 0.91 L/hour with each 1 mL/s/1.73 m2 of estimated glomerular filtration rate. Meropenem clearance was also 0.31 L/hour higher in postoperative patients with central nervous system infection. Meropenem administration by continuous infusion showed a significantly higher probability of attaining the PK/PD target than a standard 30 min infusion (95.3% vs 49.5%).

CONCLUSIONS

A daily meropenem dose of 3 g, 6 g and 10.5 g administered by continuous infusion was shown to be accurate for patients with moderate to severe renal impairment, normal renal function to mild renal impairment and augmented renal clearance, respectively.

Validation of the Pharmacokinetic Model for Anti-TNFα Clearance in Infants Exposed to Anti-TNFα During Pregnancy

BACKGROUND AND AIMS

The ECCO guideline recommends postponing live attenuated vaccines in infants exposed to anti-tumour necrosis factor alpha [anti-TNFα] in utero until drug clearance. The aim was to validate the predictive performance of the anti-TNFα clearance model.

METHODS

Newborns and data for anti-TNFα concentrations from the prospective PETIT cohort were included. The anti-TNFα clearance model was used to predict all measured concentrations in the PETIT cohort, based on the measured cord blood concentration and the mean population clearance described in the model. Bayesian maximum a posteriori optimization was used to estimate the use of drug monitoring. Predictive capability and drug monitoring were assessed through mean absolute error [MAE], root mean squared prediction error, and limits of agreement according to Bland and Altman.

RESULTS

Observed drug concentrations after birth were within the 80% prediction interval in 94% of adalimumab samples and 93% of infliximab samples. The anti-TNFα clearance model accurately predicted the concentration at 6 months after birth with an MAE of 0.03 µg/mL [SD 0.03] for adalimumab and 0.11 µg/mL [SD 0.18] for infliximab based on cord blood concentrations. Addition of an additional sample between 1 and 4 months after birth improved the predictive accuracy for infliximab (MAE 0.05 [SD 0.09]) but not for adalimumab. Guidance for use in clinical practice was formulated.

CONCLUSIONS

The validity of the anti-TNFα clearance model is high, and hence can be used to guide clinicians regarding the timing of live vaccines in infants exposed to adalimumab or infliximab in utero.

Clinical benefits of therapeutic drug monitoring of vancomycin therapy in patients with postoperative intracerebral hemorrhage: a retrospective cohort study

OBJECTIVE

The objective of this study was to investigate the clinical efficacy and safety of conducting therapeutic drug monitoring (TDM) of vancomycin in patients with postoperative intracerebral haemorrhage.

METHODS

We conducted a retrospective analysis of 435 patients who experienced postoperative cerebral haemorrhage and were treated with vancomycin in the Department of Neurosurgery of Inner Mongolia Autonomous Region People's Hospital from January 2017 to December 2021. Patients were then matched using the propensity score matching method in a ratio of 1:1. Ninety-two pairs of cases were successfully matched, and the data before and after performing vancomycin TDM were analysed.

RESULTS

After PSM, the baseline data of the two groups were balanced. There were no significant differences in the 14-day mortality and length of hospital stay (p>0.05) between the two groups. Compared with the non-TDM group, the TDM group had a higher proportion of patients with normal white blood cells (83.7% vs 56.5%, p=0.000), neutrophil count (57.6% vs 25.0%, p=0.000) and attaining desirable reductions of 80% in procalcitonin (65.2% vs 10.9%, p=0.000) and C-reactive protein (78.3% vs 41.3%, p=0.000) levels. At US$15.82 per additional TDM, TDM significantly promoted patient outcomes, as seen in improvements in the proportion of patients attaining desirable levels of white blood cells, neutrophil count, procalcitonin and C-reactive protein.

CONCLUSIONS

Vancomycin TDM is a safe and effective approach for the treatment of patients with postoperative intracerebral haemorrhage. The empirical use of TDM of vancomycin significantly improved normal values of white blood cells and neutrophil count, achieved desirable reductions of 80% in procalcitonin and C-reactive protein, and reduced nephrotoxicity in patients with postoperative intracerebral haemorrhage.

Simultaneous determination of 11 oral targeted antineoplastic drugs and 2 active metabolites by LC-MS/MS in human plasma and its application to therapeutic drug monitoring in cancer patients

Interindividual exposure differences have been identified in oral targeted antineoplastic drugs (OADs) owing to the pharmacogenetic background of the patients and their susceptibility to multiple factors, resulting in insufficient efficacy or adverse effects. Therapeutic drug monitoring (TDM) can prevent sub-optimal concentrations of OADs and improve their clinical treatment. This study aimed to develop and validate an LC-MS/MS method for the simultaneous quantification of 11 OADs (gefitinib, imatinib, lenvatinib, regorafenib, everolimus, osimertinib, sunitinib, tamoxifen, lapatinib, fruquintinib and sorafenib) and 2 active metabolites (N-desethyl sunitinib and Z-endoxifen) in human plasma. Protein precipitation was used to extract OADs from the plasma samples. Chromatographic separation was performed using an Eclipse XDB-C18 (4.6 × 150 mm, 5 μm) column with a gradient elution of the mobile phase composed of 2 mM ammonium acetate with 0.1 % formic acid in water (solvent A) and methanol (solvent B) at a flow rate of 0.8 mL/min. Mass analysis was performed using positive ion mode electrospray ionization in multiple-reaction monitoring mode. The developed method was validated following FDA bioanalytical guidelines. The calibration curves were linear over the range of 2-400 ng/mL for gefitinib, imatinib, lenvatinib, regorafenib, and everolimus; 1-200 ng/mL for osimertinib, sunitinib, N-desethyl sunitinib, tamoxifen, and Z-endoxifen; and 5-1000 ng/mL for lapatinib, fruquintinib, and sorafenib, with all coefficients of correlation above 0.99. The intra- and inter-day imprecision was below 12.81 %. This method was successfully applied to the routine TDM of gefitinib, lenvatinib, regorafenib, osimertinib, fruquintinib, and sorafenib to optimize the dosage regimens.