Therapeutic Drug Monitoring Research Articles

The Emerging Applications of Raman Spectroscopy in Clinical Oncology: A Narrative Review Focused on Circulating Tumor DNA Detection and Therapeutic Drug Monitoring

The Emerging Applications of Raman Spectroscopy in Clinical Oncology: A Narrative Review Focused on Circulating Tumor DNA Detection and Therapeutic Drug Monitoring

First fluorescence method for monitoring the doping stimulant drug solriamfetol in plasma and urine: A pharmacokinetic study in volunteers’ urine with greenness, whiteness, and blueness assessments

A green, sustainable, simple, and highly sensitive spectrofluorimetric method was developed to determine solriamfetol hydrochloride for the first time in biological fluids and dosage form. To the best of our knowledge, no Fluorimetric methods have been reported for solriamfetol determination in plasma and urine. The method is based on measuring the intrinsic fluorescence of solriamfetol hydrochloride at 522 nm after excitation at 260 nm in ammonium acetate buffer solution at pH 4. All factors influencing the response have been carefully investigated. The method was linear over a concentration range of 10 to 1800 ng/mL (r = 0.9998). The limit of detection (LOD) and limit of quantification (LOQ) values were found to be 3.2 and 9.8 ng/mL, respectively, indicating the excellent sensitivity of the proposed method. The pharmaceutical dosage form, spiked human plasma, and urine samples were successfully analyzed using the described method with average recoveries of 99.79 ± 0.739, 99.27 ± 1.885, and 99.57 ± 1.701, respectively. Plasma samples were first subjected to protein precipitation using 10 % perchloric acid, while urine samples were analyzed directly without any pretreatment. Furthermore, the suggested method was applied effectively on real human volunteers’ urine to measure renal clearance, the cumulative amount of solriamfetol excreted unchanged in the urine, and the percent of the dose recovered. The eco-friendly nature and sustainability of this work were evaluated using trending greenness, whiteness, and blueness assessment metrics. The greenness assessment tools, namely the Analytical GREEnness metric tool (AGREE), Analytical Eco-scale, and complementary green analytical procedure index (complex GAPI) were selected to prove the eco-friendly nature of the method. Additionally, whiteness and blueness assessments were conducted using the Red-Green-Blue model (RGB model), and high Blue Applicability Grade Index (BAGI), respectively. The proposed method is a promising analytical tool for routine analysis in quality control labs, therapeutic drug monitoring, and pharmacokinetics studies.

Comparison of five tacrolimus measurement methods underscore the need for a standardized method to improve clinical outcomes

Abstract Tacrolimus is a widely used drug to prevent post-transplantation organ rejection by suppressing host immune response. While its efficacy is well established, tacrolimus is also known for narrow therapeutic index and debilitating adverse effects, rendering accurate measurement for therapeutic drug monitoring essential, to minimize drug toxicity and graft loss, and maximize organ rejection prevention. Tacrolimus can be quantitated by immunoassay (IA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). However, previous pairwise studies showed significant inter-assay variabilities between different IA methods, and between IA vs LC-MS/MS, which may be associated with the fact that IA measures parent drug and its metabolites, while LC-MS/MS measures only parent drug. No clear conclusion has been drawn about the optimal method. Transplant patients may also have their tacrolimus levels measured at different laboratories by different methods, causing inter-laboratory and intra-individual variabilities which may affect tacrolimus dose adjustment and monitoring and lead to adverse clinical outcomes. Here we performed a multi-platform comparison of tacrolimus quantification by two IA and 3 LC-MS/MS assays. A total of 216 specimens were analyzed for tacrolimus levels using chemiluminescence immunoassay (ChLIA, ARCHITECT, Abbott Diagnostic) and electrochemiluminescence immunoassay (ECLIA, Elecsys, Roche Diagnostic), and three LC-MS/MS assays (assigned names LC-MS/MS A (Agilent), Q (Waters), and W (Agilent)) in five different laboratories at four institutions. In one laboratory, the same analyses were performed on two different individual instruments (LC-MS/MS W1 and W2). Comparative results using LC-MS/MS A as reference were analyzed using Deming regression analysis, Pearson correlation, Bland Altman plots and bias calculation using GraphPad Prism version 10.1.1. While the correlations between each method with the LC-MS/MS A were good (r value: lowest 0.948 (LC-MS/MS Q), highest 0.988 (LC-MS/MS W2)), the ChLIA and ECLIA showed positive absolute bias of 2.1 and 1.2 ng/mL, respectively, and proportional bias of +26% and +17%, respectively. In comparison, the absolute bias of LC-MS/MS Q, W1 and W2 were -0.7, -0.02, and -0.1 ng/mL, respectively, with proportional bias of -11%, -0.2%, and -0.7%, respectively. The LC-MS/MS platforms showed tight agreement with one another, while IA methods were noticeably different, both from each other and from the LC-MS/MS, with a consistent positive bias, more pronounced with the ChLIA than the ECLIA. Here, our data-driven approach demonstrated that LC-MS/MS is superior to IA, and among IAs, ECLIA showed higher accuracy compared to ChLIA. However, inter-assay differences remain, emphasizing a need for tacrolimus assay standardization as well as prospective clinical trials to identify the most optimal method of tacrolimus measurement and improve patient outcomes.

Development of an LC–TOF/MS Method to Quantify Camrelizumab in Human Serum

With the advantages of a high specificity, a long half-life, and a high safety, the use of antibody biologic drugs, including camrelizumab, has been rapidly increasing in clinical practice. Camrelizumab, an immune checkpoint inhibitor and humanized monoclonal antibody, is used to treat several advanced solid cancers. Measuring its concentration supports personalized dosage adjustments, influences treatment decisions for patients, strengthens the control of disease activity through therapeutic drug monitoring, and helps evaluate and prevent drug interactions in combination therapy. Because antibodies are present in complex biological matrices, quantifying monoclonal antibody drugs is challenging, and must rely on precise, selective, and reliable analytical methods. In this study, a quadrupole time-of-flight mass spectrometry TripleTOF 6600+ (AB SCIEX, Framingham, MA, USA) system equipped with a Turbo V ion source was used for the qualitative analysis of monoclonal antibodies using the data-dependent acquisition (IDA) MS/MS mode, followed by quantitative analysis using a targeted MRMHR workflow. This method showed a good linear relationship within the range of 4–160 μg/mL, with a correlation coefficient of R2 ≥ 0.996. It demonstrated an acceptable accuracy (88.95–101.18%) and precision (≤15%). Furthermore, the lower limit of quantification was found to be 4 μg/mL, with the lowest detection limit of 0.3217 μg/mL, indicating that this method is rapid, accurate, and reliable for the quantitative analysis of camrelizumab in human serum.

Enhancing Stability and Investigating Target Attainment of Benzylpenicillin in Outpatient Parenteral Antimicrobial Therapy: Insights from In Vitro and In Vivo Evaluations.

Background/Objective: Narrow-spectrum beta-lactam antibiotics such as benzylpenicillin and flucloxacillin are increasingly used in outpatient parenteral antimicrobial therapy (OPAT) programs to mitigate the adverse effects associated with broad-spectrum antibiotics. These beta-lactams require continuous administration via portable infusion devices during OPAT. However, the use of benzylpenicillin in OPAT requires special consideration because of its limited stability at elevated temperatures. Methods: We tested the benzylpenicillin stability, pH, and degradation of products in elastomeric pumps at different concentrations in saline and in buffered solution containing sodium citrate during a prolonged storage and at high temperatures (seven days at 2-8 °C followed by 24 h at 37 °C). Additionally, drug concentrations during intermittent bolus infusion and during OPAT were determined in five patients. The concentrations and degradation products of benzylpenicillin were measured using liquid chromatography mass spectrometry (LC-MS/MS). Results: Unbuffered benzylpenicillin solutions that were already degraded during refrigerator storage and analyte concentration were not measurable after 8 days. The stability of the buffered solutions was acceptable at all three of the tested concentrations (97.6 ± 1.3%, 96.3 ± 0.8%, and 94.9 ± 1.1% for 10 Mio IU, 20 Mio IU, and 40 Mio IU of benzylpenicillin). The stability was influenced by benzylpenicillin concentration, and several breakdown products were identified. Benzylpenicillin concentrations were measured in five patients during OPAT and ranged from 7.2 to 60 mg/L. Conclusions: Benzylpenicillin buffered with sodium citrate is a safe and convenient option for use in continuous infusions during OPAT and should be favored over broad-spectrum antibiotics. Therapeutic drug monitoring data indicate sufficient to high plasma levels when patients received benzylpenicillin as continuous infusions.

Quantification of deoxythioguanosine in human DNA with LC-MS/MS, a marker for thiopurine therapy optimisation.

In the treatment of diseases such as acute childhood leukaemia (ALL) and inflammatory bowel disease (IBD), the thiopurines azathioprine, 6-mercaptopurine, and 6-thioguanine are used. Thiopurines are antimetabolites and immunomodulators used to maintain remission in patients. They are all prodrugs and must be converted into thecompeting antimetabolites thioguanosine triphosphate and deoxythioguanosine triphosphate for final incorporation into RNA or DNA. The current therapeutic drug monitoring (TDM) method measures the sum of the formed metabolites in the sample, after acidic hydrolysis at high temperature. In this work, the goal is to measure these drugs closer to their pharmacological endpoints, once incorporated into DNA. After extracting DNA from whole blood, followed by DNA hydrolysis, 2'-deoxythioguanosine (dTG) and the complementary natural nucleobase 2'-deoxycytidine (dC) were measured. Chromatographic separation on a HSS T3 column followed by mass spectrometric detection was performed in multi-reaction monitoring (MRM) mode on a Xevo TQ-XS with ESI in positive mode, within 5 min. The concentration range for dTG was 0.04-5 nmol/L, and for dC, 0.1-12.5 µmol/L. The lower limit of detection was determined to a concentration of 0.003 nmol/L for dTG and 0.019 µmol/L for dC. The intra- and inter-assay imprecision for the quality controls ranged between 3.0 and 5.1% and between 8.4 and 10.9%, respectively. Sample stability for up to 4 years is shown. In summary, a sensitive method to quantify the thiopurines incorporated into DNA as dTG has been developed and will be used in further clinical studies for a better understanding of the mode of action of the thiopurines and the use of this method in TDM.

Cost-effectiveness and cost-utility of optimized mercaptopurine treatment versus placebo in ulcerative colitis patients: The randomized controlled OPTIC trial.

We assessed the cost-effectiveness and cost-utility of therapeutic drug monitoring (TDM)-guided mercaptopurine treatment compared with placebo in ulcerative colitis (UC) patients failing 5-aminosalicylates. Data were gathered alongside the randomized controlled OPTIC trial (EudraCT: 2015-005260-41). The evaluation was performed from a health care and societal perspective as cost-effectiveness and cost-utility analyses with a time horizon of one year. Volumes and costs of in-hospital care, out-of-hospital care, out-of-pocket expenses and productivity loss were assessed. The main outcomes were the extra costs per additional patient who achieved clinical remission and endoscopic improvement at 52weeks (responders) and extra costs per quality-adjusted life-year (QALY) gained. In total, 59 patients were randomized to the intervention (n=29) and control (n=30) group. Non-significant differences in costs were €63 (-€1267 to €1434; P=0.93) in favour of placebo from a health care perspective and -€742 (-€3683 to €2016; P=0.64) in favour of mercaptopurine from a societal perspective. The higher proportion of responders and a non-significant QALY difference of 0.0475 (-0.024-0.117) (P=0.184) favouring patients on mercaptopurine treatment resulted in €165 extra costs per additional responder and €1326 extra costs per QALY gained from a health care perspective. From a societal perspective, dominance over placebo was observed with cost savings of €1937 per additional responder and €15,621 per QALY gained. The probability of optimised mercaptopurine treatment being cost-effective was 0.80 at a willingness to pay per additional QALY of €20,000. TDM-based mercaptopurine treatment in UC patients failing 5-aminosalicylates is a cost-effective strategy from a societal perspective.

Linezolid Pharmacokinetics in Critically Ill Patients: Continuous Versus Intermittent Infusion.

Linezolid has been found to have considerable interindividual variability, especially in critically ill patients, which can lead to suboptimal plasma concentration. To overcome this shortcoming, several solutions have been proposed. These include using loading dose, higher maintenance doses, and dose stratification according to the patient's particularities, therapeutic drug monitoring, and drug administration via continuous infusion (CI) instead of intermittent infusion (II). In the present study, we aim to compare the pharmacokinetic (PK) parameters of linezolid after administration as II versus CI to critically ill patients. In a prospective study conducted in an intensive care unit, we compared the same two daily doses of linezolid administered via II versus CI. The serum concentration was measured, and pharmacokinetic parameters were calculated. The pharmacokinetic/pharmacodynamic (PK/PD) indices for efficacy chosen were area under the concentration-time curve at steady state divided by the minimum inhibitory concentration over 80 (AUC24-48/MIC > 80). Greater serum concentration variability was observed in the II group than in the CI group. The %T > MIC > 80% was achieved for MICs of 1 and 2 µg/mL 100% of the time, whereas for the II group, this was 93% and 73%, respectively. AUC24-48/MIC > 80 was reached in 100% of cases in the CI group compared with 87% in the II group for a MIC of 1 µg/mL. The two infusion methods may be used comparably, but utilizing CI as an alternative to II may have potential benefits, including avoiding periods of suboptimal concentrations, which may enhance safety profiles and clinical outcomes. Considering the relatively few studies performed on linezolid to date, which are increasing in number, the results of the present study may be of interest.

Are We Dosing Correctly? Population Pharmacokinetics of Cefepime in Critically Ill Pediatric Patients

Abstract Background Dosing guidelines of cefepime are well defined in healthy pediatric and adult populations but have not been extensively studied in critically ill pediatric patients. Patients who are critically ill may have significant alterations in antibiotic pharmacokinetics (PK) and pharmacodynamics (PD) due to many factors. Receipt of ECMO or CRRT may further alter PK/PD due to changes in clearance and volume of distribution and the depletion of plasma proteins. Since critically ill pediatric patients are likely to receive multiple courses of antimicrobials, optimization of drug dosing and delivery is critically important for individual patient outcomes. This study will test the hypothesis that the PK of cefepime is substantially altered in critically ill pediatric patients. Methods We prospectively enrolled patients in VUMC pediatric ICUs receiving cefepime, including those receiving ECMO or CRRT. Plasma samples were collected at opportune timepoints enriched for specific PK/PD metrics. Cefepime plasma concentrations were measured by LC-MS/MS. Weight, dose, interval, and administration time were extracted from the medical record. Monolix was used to fit population PK models using one and two-compartment models with a proportional error model. Covariate modeling was performed with a priori selected covariates: ECMO, CRRT, sex, race, ethnicity, gestational age, and creatinine clearance (CrCl). The final covariate model was used to perform probability of target attainment (PTA) analysis using Monte Carlo simulation. 6,000 subjects were simulated for each dosing regimen, with 3 weight categories (≤9 kg, 9-25 kg, and >25 kg) and 2 CrCl categories (≤90 mL/min and >90 mL/min). PTA was calculated over a grid of possible MIC values based on three targets, 65% fT>MIC, 100% fT>MIC, and 100% fT>4×MIC. Results Preliminary data from 84 pediatric participants receiving cefepime were analyzed. Of these, 9 received CRRT and 10 received ECMO. An average of 3 samples were collected per participant. A two compartment with proportional error model was selected as the base model. Population PK parameter estimates for the base model, base model with weight, and final covariate model were calculated. Inclusion of weight and CrCl significantly improved model fit. CRRT, ethnicity, and gestational age did significantly improve model fit, but their inclusion in the model did not provide evidence of being significantly better than the model with only weight and CrCl. The results from the PTA analysis are seen in Figure 1. We observed an overall ordering of PTA by dosing regimen across all three targets, with q8h 3-hour infusion having the highest PTA and q12h 30-minute infusion having the lowest PTA. Increased CrCl led to reduced PTA and as weight increased, PTA also increased. Conclusion This study will be among the first and largest to characterize cefepime PK in the critically ill pediatric population. Clinicians should incorporate local antibiograms with these population PK models to determine optimal dosing in critically ill pediatric patients. The use of extended infusions may be beneficial for PK/PD target achievement, particularly for resistant pathogens. Since clinical covariates affect PK parameters, this population may also benefit from therapeutic drug monitoring. Figure 1. Comparison of PTA among four dosing regimens of cefepime at targets of 65% fT>MIC, 100% fT>MIC, and 100% fT>4×MIC.

Cross-validation of methods for the quantitative determination of phenazepam and its active metabolite in human blood plasma at various extractions

Introduction. In conducting of therapeutic drug monitoring (TDM), often such situation arises where the drug concentration has measured by different methods or in different laboratories. To combine and analyze the data obtained with different methods, it is necessary to perform cross-validation procedure. Insufficient attention is paid to the statistical approaches used for this purpose.Aim. Performing cross-validation of different analytical methods for the quantitative determination of phenazepam (PHEN) and 3-hydroxyphenazepam (3-OH-PHEN) using the Bland – Altman analysis.Materials and methods. PHEN and 3-OH-PHEN concentrations in the blood plasma of patients (n = 100) with alcohol withdrawal syndrome were measured using high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). The quantification of both analytes in each sample was measure twice by two different methods: solid phase extraction (SPE) and supported liquid extraction (SLE). Both methods have been fully validated before the experiment began. Cross-validation was performed at the end of the experiment using data from study samples. The Bland – Altman analysis was used to evaluate accuracy and precision. Deming regression was also used to identify a systematic error between measurement results.Results and discussion. The regression equations have been obtained between concentrations both analytes measured by different sample preparation methods. 95 % confidence intervals (CI) of the regression coefficients of both equations included one, and 95 % CI of the intercepts included zero. 95 % CI of the geometric mean of the individual SLE/SPE ratios was within the acceptable range (0.87; 1.15). These results confirm the absence of the influence of quantitative methods on the measurement of both analytes concentration. 66.7 % CI of the percent difference between two measurements was within acceptable limits (–0.2; 0.2), not exceeding 20 % of the range of their mean value. This confirms the acceptable precision between the methods. The estimated CIs were displayed in the Bland – Altman plots.Conclusion. The statistical approaches used in the work have confirmed the reproducibility of the results of different sample preparation methods. In addition to cross-validation, the statistical algorithm from this paper using Bland – Altman analysis can be successfully employed to assess accuracy and precision during bioanalytical method validation and evaluation of the acceptance of analytical runs, as well as to determine the level of reproducibility of incurred samples.

Antibiotic Use in Medical-Surgical Intensive Care Units and General Wards in Latin American Hospitals

Abstract Objectives To identify antibiotic stewardship (AS) opportunities in Latin-American medical-surgical intensive care units (MS-ICUs) and general wards (Gral-wards). Methods We conducted serial cross-sectional point-prevalence surveys in MS-ICUs and Gral-wards in 41 Latin-American hospitals, between March 2022-February 2023. Patients >18 years of age on the units of interest were evaluated for antimicrobial use (AU) monthly (MS-ICUs) or quarterly (Gral-wards). Antimicrobial data were collected using a standardized form by the local AS teams and submitted to the coordinating team for analysis. Results We evaluated AU in 5,780 MS-ICU and 7,726 Gral-ward patients. Hospitals’ median bed-size was 179 (IQR 125, 330), 52% were non-profit. The aggregate AU prevalence was 53.5% in MS-ICUs and 25.5% in Gral-wards. Most (88%) antimicrobials were prescribed to treat infections, 7% for surgical prophylaxis, and 5% for medical prophylaxis. Healthcare-associated infections led to 63% of MS-ICU and 38% of Gral-ward AU. Carbapenems, piperacillin-tazobactam, intravenous (IV) vancomycin, and ampicillin-sulbactam represented 50% of all AU to treat infections. A minority of IV vancomycin targeted therapy was associated with documented methicillin-resistant Staphylococcus aureus infection or underwent therapeutic drug monitoring. In both units, 17% of antibiotics prescribed as targeted therapy represented de-escalation, while 24% and 15% in MS-ICU and Gral-ward, respectively, represented an escalation of therapy. In Gral-wards, 32% of antibiotics were used without a microbiologic culture ordered. Half of surgical prophylaxis antibiotics were prescribed for > first 24 hours. Conclusions Based on this cohort, areas to improve AU in Latin-American hospitals include antibiotic selection, de-escalation, duration of therapy, and dosing strategies.

Therapeutic drug monitoring of imatinib: is there a rationale for also quantifying its active metabolite ?

Therapeutic drug monitoring of imatinib is widely performed to individualize imatinib dosage. While N-desmethyl imatinib is an active metabolite of imatinib, its concentrations are not routinely determined. Imatinib and N-desmethyl imatinib trough plasma concentrations at steady-state were obtained from 295 patients with either chronic myeloid leukemia or gastrointestinal stromal tumor to see whether N-desmethyl imatinib provided additional information. Pharmacokinetic data were analyzed using a nonlinear mixed effect approach. Correlations between several pharmacokinetic metrics of drug exposure were evaluated. The mean value of the N-desmethyl imatinib/imatinib ratio of trough concentrations was 0.31 with half of the values between 0.23-0.37. N-desmethyl imatinib and total (i.e., N-desmethyl imatinib plus imatinib) trough plasma concentrations or area-under-the curve values were closely correlated with imatinib values. The distribution of imatinib or total concentrations between patients requiring imatinib dosage adjustment, or not, were similar. These results do not clearly support routine N-desmethyl monitoring since it does not provide additional information to imatinib data.

Clinical research for saliva-based therapeutic drug monitoring of linezolid.

Linezolid is primarily used to treat of methicillin-resistant Staphylococcus aureus and multidrug-resistant tuberculosis infections. Thrombocytopenia due to linezolid usage is a concern, and therapeutic drug monitoring has been reported to be effective in its prevention. Plasma concentrations provide valuable information for treatment decisions; however, collecting plasma samples can be burdensome for both patients and healthcare providers. Therefore, there is interest in saliva as an alternative for monitoring, considering its potential to replace plasma samples. Patients hospitalized at Hokkaido University Hospital and Hokkaido Spinal Cord Injury Center between April 2022 and July 2024, who received oral or intravenous linezolid treatment, were enrolled. The concentrations of linezolid were simultaneously measured in plasma and saliva samples. We determined the concentration profiles of linezolid in the saliva and examined the correlation between saliva and plasma linezolid concentrations. Eighteen patients receiving linezolid were enrolled. The average of saliva/plasma (S/P) concentration ratios of linezolid were 1.018. A strong correlation was found between the salivary and plasma concentrations of linezolid (R= .833, P< .001). Notably, in patients receiving intravenous administration of linezolid, the correlation was even more pronounced (R= .885, P< .001). Additionally, when focusing on the S/P ratio of the trough concentrations in the morning and at night, the S/P ratios at night were much closer to 1.0. The concentrations of linezolid in plasma and saliva were similar, indicating their potential applicability in clinical settings. The monitoring of linezolid concentrations in saliva has been shown to be particularly suitable for patients receiving intravenous administration.

Personalization of pharmacotherapy with sirolimus based on volumetric absorptive microsampling (VAMS) in pediatric renal transplant recipients-from LC-MS/MS method validation to clinical application.

The benefits of pharmacotherapy with sirolimus (SIR) in pediatric transplant recipients are well established. Traditionally, whole blood samples have been used to measure SIR concentrations. Volumetric Absorptive Microsampling (VAMS) is an alternative sampling strategy suitable for Therapeutic Drug Monitoring (TDM). In this study, we developed and validated two liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods for determining SIR concentrations in whole blood (WB) and capillary whole blood samples collected using a VAMS-Mitra™ device. We used protein precipitation during WB sample preparation and dispersive liquid-liquid microextraction (DLLME) with methyl tert-butyl ether for VAMS sample preparation to optimise the analyte extraction process. The described validation protocols were cross-validated, confirming the equivalence of the whole-blood and VAMS-based methods. Furthermore, the developed methods were evaluated in two three-level rounds of an external proficiency-testing scheme. The analytical methods were successfully validated within the calibration range of SIR (0.5-60 ng/ml). The validation parameters met the European Medicines Agency (EMA) and the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDM&CT) acceptance criteria. No hematocrit (tested in the range of 24.3-64.1%), matrix, or carry-over effects were observed. Cross-validation confirmed the interchangeability between VAMS-LC-MS/MS and WB-LC-MS/MS methods. The developed methods were successfully implemented for SIR determination in 140 clinical samples (70 each of WB and VAMS) from pediatric renal transplant recipients, demonstrating their practicality and reliability. The VAMS-based method has been rigorously tested and is clinically equivalent to the reference WB-LC-MS/MS method. Additionally, clinical validation confirmed the utility of the presented methods for TDM of the SIR in the pediatric population after renal transplantation.

Liquid Chromatography-Tandem Mass Spectrometry Method for Therapeutic Drug Monitoring of Dalbavancin in Plasma of Pediatric and Young Adult Patients.

Dalbavancin, an antimicrobial lipoglycopeptide, is authorized in Europe for treating acute bacterial infections of the skin and skin structures in adults and pediatric patients aged 3 months and older. However, off-label dosing regimens have been proposed for various indications beyond acute bacterial infections of the skin and skin structures. This study presents a novel bioanalytical method using liquid chromatography-tandem mass spectrometry to quantify dalbavancin in low-volume plasma samples (50 μL). The method underwent validation in accordance with international guidelines for bioanalytical method validation and was applied to 9 clinical samples obtained from pediatric and young adult patients undergoing dalbavancin therapy. Liquid chromatography-tandem mass spectrometry analyses were conducted at the G. Gaslini Institute in Genoa, Italy, utilizing an Ultimate 3000 ultra high performance liquid chromatography system coupled to a TSQ Quantiva Triple Quadrupole system (Thermo Fisher Scientific, Milan, Italy). The analytical procedure involved the addition of deuterated dalbavancin as internal standard and a rapid extraction from 50 µL of human plasma, followed by chromatographic separation on a Thermo Scientific Accucore Polar Premium column. Accurate quantification of the analyte was achieved through multiple reaction monitoring detection. The assay exhibited linearity within the concentration range of 0.66-400 mcg/mL in plasma, demonstrating accuracy and reproducibility in the absence of matrix effects. Stability testing was conducted on both quality controls and real samples to establish a robust protocol under real-life conditions. This fast and reliable dalbavancin quantitation method could improve current pediatric clinical practice by enabling data collection for future dose recommendations in special patient populations.

Population pharmacokinetics of tacrolimus whole blood and peripheral blood mononuclear cell concentrations in stable kidney-transplanted patients.

Therapeutic drug monitoring of tacrolimus based on whole blood drug concentrations is routinely performed. The concentration of tacrolimus in peripheral blood mononuclear cells (PMBCs) is likely to better reflect drug exposure at the treatment target site. We aimed to describe the relationship between tacrolimus whole blood and PBMC concentrations, and the influence of patient characteristics on this relationship by developing a population pharmacokinetic model. We prospectively enrolled 63 stable adult kidney-transplanted patients and collected dense (12-h, n = 18) or sparse (4-h, n = 45) pharmacokinetic profiles of tacrolimus. PBMCs were isolated from whole blood (Ficoll density gradient centrifugation), and drug concentrations in whole blood and PBMCs were analysed using liquid chromatography-mass spectrometry. Patient genotype (CYP3A4/5, ABCB1, NR1I2) was assessed with PCR. Population pharmacokinetic modelling and statistical evaluation was performed using NONMEM. Tacrolimus whole blood concentrations were well described using a two-compartment pharmacokinetic model with a lag-time and first-order absorption and elimination. Tacrolimus PBMC concentrations were best estimated from whole blood concentrations with the use of a scaling factor, the ratio of whole blood to PBMC concentrations (RC:PBMC), which was the extent of tacrolimus distribution into PBMC. CYP3A5*1 non-expressors and NR1I2-25 385T allele expressors demonstrated higher RC:PBMC ratios of 42.4% and 60.7%, respectively. Tacrolimus PBMC concentration could not be accurately predicted from whole blood concentrations and covariates because of significant residual unexplained variability in the distribution of tacrolimus into PBMCs and may need to be measured directly if required for future studies.

A multicentric, randomized, controlled clinical trial to study the impact of bedside model-informed precision dosing of vancomycin in critically ill children—BENEFICIAL trial

BackgroundVancomycin is a commonly prescribed antibiotic to treat serious Gram-positive infections in children. The efficacy of vancomycin is known to be directly related to the pharmacokinetic/pharmacodynamic (PK/PD) index of the area under the concentration–time curve (AUC) divided by the minimal inhibitory concentration (MIC) of the pathogen. In most countries, steady-state plasma concentrations are used as a surrogate parameter for this target AUC/MIC, but this practice has some drawbacks. Hence, AUC-based dosing using model-informed precision dosing (MIPD) tools has been proposed for increasing the target attainment rate and reducing vancomycin-related nephrotoxicity. Solid scientific evidence for these claimed benefits is lacking in children. This randomized controlled trial aims to investigate the large-scale utility of MIPD dosing of vancomycin in critically ill children.MethodsParticipants from 14 neonatal intensive care, pediatric intensive care, and pediatric hemo-oncology ward units from 7 hospitals are randomly allocated to the intervention or standard-of-care comparator group. In the intervention group, a MIPD dosing calculator is used for AUC-based dosing, in combination with extra sampling for therapeutic drug monitoring in the first hours of treatment, as compared to standard-of-care. An AUC24h between 400 and 600 is targeted, assuming an MIC of 1 mg/L. Patients in the comparator group receive standard-of-care dosing and monitoring according to institutional guidelines. The primary endpoint is the proportion of patients reaching the target AUC24h/MIC of 400–600 between 24 and 48 h after the start of vancomycin treatment. Secondary endpoints are the proportion of patients with (worsening) acute kidney injury during vancomycin treatment, the proportion of patients reaching target AUC24h/MIC of 400–600 between 48 and 72 h after the start of vancomycin treatment, time to clinical cure, ward unit length-of-stay, hospital length-of-stay, and 30-day all-cause mortality.DiscussionThis trial will clarify the propagated benefits and provide new insights into how to optimally monitor vancomycin treatment in critically ill children.Trial registrationEudract number: 2019–004538-40. Registered on 2020–09-08ClinicalTrials.gov NCT046666948. Registered on 2020–11-28

Therapeutic drug monitoring of linezolid in Chinese premature neonates: a population pharmacokinetic analysis and dosage optimization.

This study aimed to develop a pharmacokinetic model of linezolid in premature neonates and evaluate and optimize the administration regimen. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to detect the blood concentration data of 54 premature neonates after intravenous administration of linezolid, and the relevant clinical data were collected. The population pharmacokinetic (PPK) model was established by nonlinear mixed effects modeling. Based on the final model parameters, the optimal administration regimen of linezolid in premature neonates with different body surface areas (BSA) was simulated and evaluated. The pharmacokinetic properties of linezolid in premature neonates are best described by a single-compartment model with primary elimination. The population typical values for apparent volume of distribution and clearance were 0.783 L and 0.154 L/h, respectively. BSA was a statistically significant covariate with clearance (CL) and volume of distribution (Vd). Monte Carlo simulations showed that the optimal administration regimen for linezolid in premature neonates was 6 mg/kg q8h for BSA 0.11 m2, 7 mg/kg q8h for BSA 0.13 m2, and 9 mg/kg q8h for BSA 0.15 m2 with minimum inhibitory concentration (MIC) ≤1 mg/L, 7 mg/kg q8h for BSA 0.11 m2, 8 mg/kg q8h for BSA 0.13 m2, and 10 mg/kg q8h for BSA 0.15 m2 with MIC = 2 mg/L. A pharmacokinetic model was developed to predict the blood concentration on linezolid in premature neonates. Based on this model, the optimal administration regimen of linezolid in premature neonates needs to be individualized according to different BSA levels.

Impacts of age and BMI on vancomycin model choice in a Bayesian software: Lessons from a very large multi-site retrospective study.

Model-informed precision dosing (MIPD) optimizes drug doses based on pharmacokinetic (PK) model predictions, necessitating careful selection of models tailored to patient characteristics. This study evaluates the predictive performance of various vancomycin PK models across diverse age and BMI categories, drawing insights from a large multi-site database. Adults receiving vancomycin intravenous therapy at United States health systems between January 1, 2022, and December 31, 2023, were included. Patient demographics, vancomycin administration records, and therapeutic drug monitoring levels (TDMs) were collected from the InsightRX database. Age and body mass index (BMI)-based subgroups were formed to assess model performance, with predictions made iteratively. The optimal model for each age-BMI subgroup was chosen based on predefined criteria: models were filtered for mean percentage error (MPE) ≤ 20% and normalized root mean squared error (RMSE) < 8 mg/L, and then the most accurate among them was selected. A total of 384,876 treatment courses across 155 US health systems were analyzed, contributing 841,604 TDMs. Eleven models were compared, showing varying accuracy across age-BMI categories (41%-73%), with higher accuracy observed once TDMs were available for Bayesian estimates of individual PK parameters. Models performed more poorly in younger adults compared to older adults, and the optimal model differed depending on age-BMI categories and prediction methods. Notably, in the a priori period, the Colin model performed best in adults aged 18-64 years across most BMI categories; the Goti/Tong model performed best in the older, non-obese adults; and the Hughes model performed best in many of the obese categories. Our study identifies specific vancomycin PK models that demonstrate superior predictions across age-BMI categories in MIPD applications. Our findings underscore the importance of tailored model selection for vancomycin management, especially highlighting the need for improved models in younger adult patients. Further research into the clinical implications of model performance is warranted to enhance patient care outcomes.

Automated calculation and reporting of vancomycin area under the concentration-time curve: a simplified single-trough concentration-based equation approach.

Vancomycin, a crucial antibiotic for Gram-positive bacterial infections, requires therapeutic drug monitoring (TDM). Contemporary guidelines advocate for AUC-based monitoring; however, using Bayesian programs for AUC estimation poses challenges. We aimed to develop and evaluate a simplified AUC estimation equation using a steady-state trough concentration (Ctrough) value. Utilizing 1,034 TDM records from 580 general hospitalized patients at a university-affiliated hospital in Ulsan, we created an equation named SSTA that calculates the AUC by applying Ctrough, body weight, and single dose as input variables. External validation included 326 records from 163 patients at a university-affiliated hospital in Seoul (EWUSH) and literature data from 20 patients at a university-affiliated hospital in Bangkok (MUSI). It was compared with other AUC estimation models based on the Ctrough, including a linear regression model (LR), a sophisticated model based on the first-order equation (VancoPK), and a Bayesian model (BSCt). Evaluation metrics, such as median absolute percentage error (MdAPE) and the percentage of observations within ±20% error (P20), were calculated. External validation using the EWUSH data set showed that SSTA, LR, VancoPK, and BSCt had MdAPE values of 6.4, 10.1, 6.6, and 7.5% and P20 values of 87.1, 82.5, 87.7, and 83.4%, respectively. External validation using the MUSI data set showed that SSTA, LR, and VancoPK had MdAPEs of 5.2, 9.4, and 7.2%, and P20 of 95, 90, and 95%, respectively. Owing to its decent AUC prediction performance, simplicity, and convenience for automated calculation and reporting, SSTA could be used as an adjunctive tool for the AUC-based TDM.