Assessment of the practical impact of adjusting beta-lactam dosages based on therapeutic drug monitoring in critically ill adult patients: a systematic review and meta-analysis of randomized clinical trials and observational studies.

An estimated 70% of critically ill patients receive antibiotics, most frequently beta-lactams. The pharmacokinetic properties of these substances in this patient population are poorly predictable. Therapeutic drug monitoring (TDM) is helpful in making personalized decisions in this field, but its overall impact as a clinical decision-supporting tool is debated. We aimed to evaluate the clinical implications of adjusting beta-lactam dosages based on TDM in the critically ill population by performing a systematic review and meta-analysis of available investigations. Randomized controlled trials and observational studies were retrieved by searching three major databases. The intervention group received TDM-guided beta-lactam treatment, that is, at least one dose reconsideration based on the result of the measurement of drug concentrations, while TDM-unadjusted dosing was employed in the comparison group. The outcomes were evaluated using forest plots with random-effects modeling and subgroup analysis. Eight eligible studies were identified, including 1044 patients in total. TDM-guided beta-lactam treatment was associated with improved clinical cure from infection [odds ratio (OR): 2.22 (95% confidence interval (CI): 1.78-2.76)] and microbiological eradication [OR: 1.72 (CI: 1.05-2.80)], as well as a lower probability of treatment failure [OR: 0.47 (CI: 0.36-0.62)], but the heterogeneity of studies was remarkably high, especially in terms of mortality (70%). The risk of bias was moderate. While the TDM-guided administration of beta-lactams to critically ill patients has a favorable impact, standardized study designs and larger sample sizes are required for developing evidence-based protocols in this field.

Reference data on estrogen metabolome in healthy pregnancy.

INTRODUCTION: Estrogen hormones and their metabolites are implicated in the maintenance of healthy pregnancy and adequate fetal development. Abnormal levels were related to increased risk of pregnancy complications, particularly preeclampsia. Our aims were (1) to develop a methodological platform for the comprehensive assessment of estrogen metabolome in pregnancy; (2) to collect healthy reference data for relevant elements of estrogen metabolome in each trimester; (3) to assess unconjugated fractions of the estrogen metabolome, (4) to assess the dominant metabolic pathways of estrogen compounds. METHODS: We enrolled healthy pregnant mothers between gestational week 5-15 (on the confirmation of pregnancy; 79 samples), gestational weeks 19-27 (70 samples), and gestational week 34-39 (54 samples). A method employing liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed to assess estrone, 17-beta-estradiol, estriol levels, and their metabolites as conjugated and unconjugated forms. Descriptive statistics were used to characterize the level of compounds in each trimester. RESULTS: Estrone, 17-beta-estradiol and estriol levels are dramatically increasing with the advancement of pregnancy. Measured levels were in a very wide range. 17-beta-estradiol is neither glucuronated nor sulphated. To the contrary, estriol and estrone are significantly conjugated; unconjugated fraction is <15% of total hormone levels in any trimester. Regarding metabolism, 4-methoxy-estradiol and 17-epiestriol were not detected. CONCLUSION: We concluded that (1) the levels of estrogen compounds and metabolites increase with advancing gestational age; (2) the wide ranges of levels challenge the establishment of a healthy reference range for clinical purposes; (3) 17-beta-estradiol is not conjugated significantly; (4) 4-methylation and 17-epimerization pathways of estrogens are negligible with our LC-MS/MS method.

Modeling Pharmacokinetics in Individual Patients Using Therapeutic Drug Monitoring and Artificial Population Quasi-Models: A Study with Piperacillin.

Population pharmacokinetic (pop-PK) models constructed for model-informed precision dosing often have limited utility due to the low number of patients recruited. To augment such models, an approach is presented for generating fully artificial quasi-models which can be employed to make individual estimates of pharmacokinetic parameters. Based on 72 concentrations obtained in 12 patients, one- and two-compartment pop-PK models with or without creatinine clearance as a covariate were generated for piperacillin using the nonparametric adaptive grid algorithm. Thirty quasi-models were subsequently generated for each model type, and nonparametric maximum a posteriori probability Bayesian estimates were established for each patient. A significant difference in performance was found between one- and two-compartment models. Acceptable agreement was found between predicted and observed piperacillin concentrations, and between the estimates of the random-effect pharmacokinetic variables obtained using the so-called support points of the pop-PK models or the quasi-models as priors. The mean squared errors of the predictions made using the quasi-models were similar to, or even considerably lower than those obtained when employing the pop-PK models. Conclusion: fully artificial nonparametric quasi-models can efficiently augment pop-PK models containing few support points, to make individual pharmacokinetic estimates in the clinical setting.

Role of CB1 Cannabinoid Receptors in Vascular Responses and Vascular Remodeling of the Aorta in Female Mice.

Both the endocannabinoid system (ECS) and estrogens have significant roles in cardiovascular control processes. Cannabinoid type 1 receptors (CB1Rs) mediate acute vasodilator and hypotensive effects, although their role in cardiovascular pathological conditions is still controversial. Estrogens exert cardiovascular protection in females. We aimed to study the impact of ECS on vascular functions. Experiments were performed on CB1R knockout (CB1R KO) and wild-type (WT) female mice. Plasma estrogen metabolite levels were determined. Abdominal aortas were isolated for myography and histology. Vascular effects of phenylephrine (Phe), angiotensin II, acetylcholine (Ach) and estradiol (E2) were obtained and repeated with inhibitors of nitric oxide synthase (NOS, Nω-nitro-L-arginine) and of cyclooxygenase (COX, indomethacin). Histological stainings (hematoxylin-eosin, resorcin-fuchsin) and immunostainings for endothelial NOS (eNOS), COX-2, estrogen receptors (ER-α, ER-ß) were performed. Conjugated E2 levels were higher in CB1R KO compared to WT mice. Vasorelaxation responses to Ach and E2 were increased in CB1R KO mice, attenuated by NOS-inhibition. COX-inhibition decreased Phe-contractions, while it increased Ach-relaxation in the WT group but not in the CB1R KO. Effects of indomethacin on E2-relaxation in CB1R KO became opposite to that observed in WT. Histology revealed lower intima/media thickness and COX-2 density, higher eNOS and lower ER-ß density in CB1R KO than in WT mice. CB1R KO female mice are characterized by increased vasorelaxation associated with increased utilization of endothelial NO and a decreased impact of constrictor prostanoids. Our results indicate that the absence or inhibition of CB1Rs may have beneficial vascular effects.

[Challenge in modern intensive care: chronic critical illness - pathophysiology and therapeutic options]. / A modern intenzív terápia kihívása: az elhúzódó kritikus állapot kórélettani háttere és terápiás lehetoségei.

The recent developments in intensive care have resulted in improved survival rates of patients treated with acute organ deficiency. As a consequence, the rate of those who survive the acute phase and subsequently require protracted organ support due to persisting organ dysfunction has been growing. Several survivors display chronic health status deterioration leading to prolonged rehabilitation or nursing, and repeated hospitalizations. The condition developed following the survival of the acute phase and requiring long-lasting intensive care is frequently termed as chronic critical illness (CCI). Several definitions exist, most of these are based on the number of ventilator days, or days of stay at the intensive care unit. Nevertheless, in spite of the initially heterogenous etiology of the acute illness, the complications associated with CCI, as well as the pathophysiological processes underlying these, are relatively uniform. This causes CCI to be a unique clinical syndrome characterized by the development of secondary infections, myopathy, central and peripheral neuropathy, and typical alterations of the hormonal and immune system functions. The outcome is heavily influenced by the frailty and comorbidities of the patient, in addition to the severity of the acute illness. The treatment of CCI patients presents a complicated task requiring multidisciplinary view and individualized therapeutic measures. Since the aging of the population and the continuously improving success rates in overcoming acute conditions also facilitate the development of CCI, the systematic overview of the underlying pathophysiological processes is pivotal for the optimization of the medical, nursing, social and economical burden presented by this syndrome. Orv Hetil. 2023; 164(18): 702-712.

Risk Estimation of Gestational Diabetes Mellitus in the First Trimester.

CONTEXT: There is no early, first-trimester risk estimation available to predict later (gestational week 24-28) gestational diabetes mellitus (GDM); however, it would be beneficial to start an early treatment to prevent the development of complications. OBJECTIVE: We aimed to identify early, first-trimester prediction markers for GDM. METHODS: The present case-control study is based on the study cohort of a Hungarian biobank containing biological samples and follow-up data from 2545 pregnant women. Oxidative-nitrative stress-related parameters, steroid hormone, and metabolite levels were measured in the serum/plasma samples collected at the end of the first trimester from 55 randomly selected control and 55 women who developed GDM later. RESULTS: Pregnant women who developed GDM later during the pregnancy were older and had higher body mass index. The following parameters showed higher concentration in their serum/plasma samples: fructosamine, total antioxidant capacity, testosterone, cortisone, 21-deoxycortisol; soluble urokinase plasminogen activator receptor, dehydroepiandrosterone sulfate, dihydrotestosterone, cortisol, and 11-deoxycorticosterone levels were lower. Analyzing these variables using a forward stepwise multivariate logistic regression model, we established a GDM prediction model with a specificity of 96.6% and sensitivity of 97.5% (included variables: fructosamine, cortisol, cortisone, 11-deoxycorticosterone, SuPAR). CONCLUSION: Based on these measurements, we accurately predict the development of later-onset GDM (24th-28th weeks of pregnancy). Early risk estimation provides the opportunity for targeted prevention and the timely treatment of GDM. Prevention and slowing the progression of GDM result in a lower lifelong metabolic risk for both mother and offspring.

Therapeutic Monitoring of Orally Administered, Small-Molecule Anticancer Medications with Tumor-Specific Cellular Protein Targets in Peripheral Fluid Spaces-A Review.

Orally administered, small-molecule anticancer drugs with tumor-specific cellular protein targets (OACD) have revolutionized oncological pharmacotherapy. Nevertheless, the differences in exposure to these drugs in the systemic circulation and extravascular fluid compartments have led to several cases of therapeutic failure, in addition to posing unknown risks of toxicity. The therapeutic drug monitoring (TDM) of OACDs in therapeutically relevant peripheral fluid compartments is therefore essential. In this work, the available knowledge regarding exposure to OACD concentrations in these fluid spaces is summarized. A review of the literature was conducted by searching Embase, PubMed, and Web of Science for clinical research articles and case reports published between 10 May 2001 and 31 August 2022. Results show that, to date, penetration into cerebrospinal fluid has been studied especially intensively, in addition to breast milk, leukocytes, peripheral blood mononuclear cells, peritoneal fluid, pleural fluid, saliva and semen. The typical clinical indications of peripheral fluid TDM of OACDs were (1) primary malignancy, (2) secondary malignancy, (3) mental disorder, and (4) the assessment of toxicity. Liquid chromatography-tandem mass spectrometry was most commonly applied for analysis. The TDM of OACDs in therapeutically relevant peripheral fluid spaces is often indispensable for efficient and safe treatments.

Assessment of Antibiotic Pharmacokinetics, Molecular Biomarkers and Clinical Status in Critically Ill Adults Diagnosed with Community-Acquired Pneumonia and Receiving Intravenous Piperacillin/Tazobactam and Hydrocortisone over the First Five Days of Intensive Care: An Observational Study (STROBE Compliant).

Severe community-acquired pneumonia (CAP) is a condition that frequently requires intensive care and, eventually, can cause to death. Piperacillin/tazobactam antibiotic therapy is employed as an empiric intravenous regimen, in many cases supplemented with intravenous bolus hydrocortisone treatment. The individual and condition-dependent pharmacokinetic properties of these drugs may lead to therapeutic failure. The impact of systemic inflammation, as well as of hydrocortisone on the altered pharmacokinetics of piperacillin is largely unknown. The protocol of a clinical study aimed at the characterization of the pharmacokinetics of piperacillin and tazobactam and its association with the concentrations of inflammatory markers and adrenal steroids during CAP therapy will be investigated in up to 40 critically ill patients. The serum concentrations of piperacillin and tazobactam, cortisol, cortisone, corticosterone and 11-deoxycortisol and interleukin-6 levels, as well as routine clinical chemistry and hematology parameters will be monitored from the beginning of treatment for up to five days. Nonparametric population pharmacokinetic modeling and Monte-Carlo simulations will be performed to make estimates of the pharmacokinetics of piperacillin and tazobactam and the probability of pharmacokinetic-pharmacodynamic target attainment. The observed individual characteristics and changes will be correlated with clinical and laboratory findings. The protocol of the observational study will be designed following the STROBE guideline.

A High-Throughput Clinical Laboratory Methodology for the Therapeutic Monitoring of Ibrutinib and Dihydrodiol Ibrutinib.

Ibrutinib (IBR) is an oral anticancer medication that inhibits Bruton tyrosine kinase irreversibly. Due to the high risk of adverse effects and its pharmacokinetic variability, the safe and effective use of IBR is expected to be facilitated by precision dosing. Delivering suitable clinical laboratory information on IBR is a prerequisite of constructing fit-for-purpose population and individual pharmacokinetic models. The validation of a dedicated high-throughput method using liquid chromatography-mass spectrometry is presented for the simultaneous analysis of IBR and its pharmacologically active metabolite dihydrodiol ibrutinib (DIB) in human plasma. The 6 h benchtop stability of IBR, DIB, and the active moiety (IBR+DIB) was assessed in whole blood and in plasma to identify any risk of degradation before samples reach the laboratory. In addition, four regression algorithms were tested to determine the optimal assay error equations of IBR, DIB, and the active moiety, which are essential for the correct estimation of the error of their future nonparametric pharmacokinetic models. The noncompartmental pharmacokinetic properties of IBR and the active moiety were evaluated in three patients diagnosed with chronic lymphocytic leukemia to provide a proof of concept. The presented methodology allows clinical laboratories to efficiently support pharmacokinetics-based precision pharmacotherapy with IBR.

Clinical and diagnostic relevance of asymmetric and symmetric dimethyl arginine (ADMA/SDMA). / Az aszimmetrikus és a szimmetrikus dimetilált arginin (ADMA/SDMA) klinikai és diagnosztikai jelentosége.

Összefoglaló. Régóta folynak kutatások olyan újabb biomarkerek azonosítására, amelyek segítik a krónikusan progrediáló, úgynevezett civilizációs betegségek - például cardiovascularis kórképek, vesefunkció-beszukülés - korai felismerését. Az aszimmetrikus és a szimmetrikus dimetil-arginin (ADMA és SDMA) ketto azon paraméterek közül, amelyek biológiai hatásai évtizedek óta ismertek ugyan, ám biomarkerként egyelore nem terjedtek el a humán orvosi-diagnosztikai gyakorlatban. A fehérjearginin-metiltranszferázok katalizálta folyamatban L-argininbol keletkezo vegyületek a nitrogén-monoxid-szintáz aktivitásának gátlói. Mivel a nitrogén-monoxid számos biológiai folyamat kulcsszereploje - gátolja az érpálya simaizomsejtjeinek relaxációját, csökkenti a thrombocytaaggregációt, és gyulladáscsökkento hatást fejt ki -, termelodésének zavarai megnövelik a magas vérnyomás és cardiovascularis betegségek kialakulásának kockázatát. Áttekinto közleményünkben az ADMA és az SDMA mint lehetséges új diagnosztikai markerek, valamint a társadalmi és orvosszakmai szempontból is kihívást jelento betegségek kapcsolatának bemutatását tuztük ki célul. Orv Hetil. 2022; 163(13): 500-505. Summary. Research has long been underway to identify additional biomarkers that will help in the early detection of chronic diseases of civilization, such as cardiovascular disease and renal impairment. Asymmetric and symmetric dimethyl arginine (ADMA and SDMA), two of the parameters whose biological effects have been known for decades, have not yet been widely used as biomarkers in human medical-diagnostic practice. In a process catalyzed by protein arginine methyltransferases, compounds derived from L-arginine are inhibitors of nitric oxide synthase activity. Because nitric oxide is a key player in many biological processes - for instance, inhibiting the relaxation of vascular smooth muscle cells, reducing platelet aggregation, and having anti-inflammatory effect -, disturbances in its production increase the risk of developing high blood pressure and cardiovascular disease. Therefore, in our review paper, we aimed to present the relationship between ADMA and SDMA as possible new diagnostic markers and socially and physically challenging diseases. Orv Hetil. 2022; 163(13): 500-505.

Adrenal, Gonadal and Peripherally Steroid Changes in Response to Extreme Physical Stress for Characterizing Load Capacity in Athletes.

Athletes are often exposed to extreme physical stress during training or competitions. The consequent activation of the hypothalamus-hypophysis-adrenal (HPA) axis results in intensified steroid hormone production in the adrenal cortex. We determined the impact of an acute extreme physical stress on adrenal and gonadal steroidogenesis in healthy male professional athletes (n = 40). The subjects underwent an extreme physical load test until total voluntary fatigue between 14:00 and 18:00 when the hormone levels are relatively stable. Blood was taken before the start (baseline), at the peak load (peak), and 30 min following completion of the exercise (recovery). The vital parameters, lactate levels, and blood levels of the 14 steroid hormones were recorded. The multivariate statistical analysis of the results revealed that all monitored hormone levels increased upon stress. Significant changes in steroid concentrations were detected at peak versus baseline, peak versus recovery, and at baseline versus recovery. The mineralocorticoid (including aldosterone and corticosterone), glucocorticoid (11-deoxycortisol and cortisol), and androgen (androstenedione, dehydroepiandrosterone, and dehydroepiandrosterone sulfate) pathways, as well as gonadal testosterone synthesis are activated simultaneously under extreme physical load. The profiling of adrenal and gonadal steroid biosynthesis in athletes may help the characterization of their loading capacity.

Sex-related differences of early cardiac functional and proteomic alterations in a rat model of myocardial ischemia.

BACKGROUND: Reduced cardiovascular risk in premenopausal women has been the focus of research in recent decades. Previous hypothesis-driven experiments have highlighted the role of sex hormones on distinct inflammatory responses, mitochondrial proteins, extracellular remodeling and estrogen-mediated cardioprotective signaling pathways related to post-ischemic recovery, which were associated with better cardiac functional outcomes in females. We aimed to investigate the early, sex-specific functional and proteomic changes following myocardial ischemia in an unbiased approach. METHODS: Ischemia was induced in male (M-Isch) and female (F-Isch) rats with sc. injection of isoproterenol (85 mg/kg) daily for 2 days, while controls (M-Co, F-Co) received sc. saline solution. At 48 h after the first injection pressure-volume analysis was carried out to assess left ventricular function. FFPE tissue slides were scanned and analyzed digitally, while myocardial proteins were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using isobaric labeling. Concentrations of circulating steroid hormones were measured with LC-MS/MS. Feature selection (PLS and PLS-DA) was used to examine associations among functional, proteomic and hormonal datasets. RESULTS: Induction of ischemia resulted in 38% vs 17% mortality in M-Isch and F-Isch respectively. The extent of ischemic damage to surviving rats was comparable between the sexes. Systolic dysfunction was more pronounced in males, while females developed a more severe impairment of diastolic function. 2224 proteins were quantified, with 520 showing sex-specific differential regulation. Our analysis identified transcriptional, cytoskeletal, contractile, and mitochondrial proteins, molecular chaperones and the extracellular matrix as sources of disparity between the sexes. Bioinformatics highlighted possible associations of estrogens and their metabolites with early functional and proteomic alterations. CONCLUSIONS: Our study has highlighted sex-specific alterations in systolic and diastolic function shortly after ischemia, and provided a comprehensive look at the underlying proteomic changes and the influence of estrogens and their metabolites. According to our bioinformatic analysis, inflammatory, mitochondrial, chaperone, cytoskeletal, extracellular and matricellular proteins are major sources of intersex disparity, and may be promising targets for early sex-specific pharmacologic interventions.

Identification of disease- and headache-specific mediators and pathways in migraine using blood transcriptomic and metabolomic analysis.

BACKGROUND: Recent data suggest that gene expression profiles of peripheral white blood cells can reflect changes in the brain. We aimed to analyze the transcriptome of peripheral blood mononuclear cells (PBMC) and changes of plasma metabolite levels of migraineurs in a self-controlled manner during and between attacks. METHODS: Twenty-four patients with migraine were recruited and blood samples were collected in a headache-free (interictal) period and during headache (ictal) to investigate disease- and headache-specific alterations. Control samples were collected from 13 age- and sex-matched healthy volunteers. RNA was isolated from PBMCs and single-end 75 bp RNA sequencing was performed using Illumina NextSeq 550 instrument followed by gene-level differential expression analysis. Functional analysis was carried out on information related to the role of genes, such as signaling pathways and biological processes. Plasma metabolomic measurement was performed with the Biocrates MxP Quant 500 Kit. RESULTS: We identified 144 differentially-expressed genes in PBMCs between headache and headache-free samples and 163 between symptom-free patients and controls. Network analysis revealed that enriched pathways included inflammation, cytokine activity and mitochondrial dysfunction in both headache and headache-free samples compared to controls. Plasma lactate, succinate and methionine sulfoxide levels were higher in migraineurs while spermine, spermidine and aconitate were decreased during attacks. CONCLUSIONS: It is concluded that enhanced inflammatory and immune cell activity, and oxidative stress can play a role in migraine susceptibility and headache generation.

A pharmacokinetics-based approach to the monitoring of patient adherence to atorvastatin therapy.

The inadequate adherence of patients whose hyperlipidemia is treated with atorvastatin (ATR) to medical instructions presents a serious health risk. Our aim was to develop a flexible approach based on therapeutic drug monitoring (TDM), nonparametric population pharmacokinetic modeling, and Monte Carlo simulation to differentiate adherent patients from partially and nonadherent individuals in a nonrandomized, unicentric, observational study. Sixty-five subjects were enrolled. Nonparametric, mixed-effect population pharmacokinetic models of the sums of atorvastatin and atorvastatin lactone concentrations (ATR+ATRL) and of the concentrations of the acid and lactone forms of ATR and its 2- and 4-hydroxylated pharmacologically active metabolites (ATR+MET) were elaborated by including the TDM results obtained in 128 samples collected from thirty-nine subjects. Monte Carlo simulation was performed based on the elaborated models to establish the probabilities of attaining a specific ATR+ATRL or ATR+MET concentration in the range of 0.002-10 nmol (mg dose)-1 L-1 at 1-24 h postdose by adherent, partially adherent, and nonadherent patients. The results of the simulations were processed to allow the estimation of the adherence of further 26 subjects who were phlebotomized at sampling times of 2-20 h postdose by calculating the probabilities of attaining the ATR+ATRL and ATR+MET concentrations measured in these subjects in adherent, partially adherent, and nonadherent individuals. The best predictive values of the estimates of adherence could be obtained with sampling at early sampling times. 61.54% and 38.46% of subjects in the adherence testing set were estimated to be fully and partially adherent, respectively, while in all cases the probability of nonadherence was extremely low. The evaluation of patient adherence to ATR therapy based on pharmacokinetic modeling and Monte Carlo simulation has important advantages over the collection of trough samples and the use of therapeutic ranges.

Sensitive, High-Throughput Liquid Chromatography-Tandem Mass Spectrometry Analysis of Atorvastatin and Its Pharmacologically Active Metabolites in Serum for Supporting Precision Pharmacotherapy.

The antihyerlipidemic drug atorvastatin (ATR) is used worldwide as part of the strategy to prevent cardiovascular events. The high prevalence of patient nonadherence remains an important challenge which could be addressed efficiently by precision pharmacotherapy based on therapeutic drug monitoring (TDM). ATR is metabolized to pharmacologically active metabolites, and evidence shows that the sums of ATR acid and lactone form concentrations (ATR + ATRL), or of ATR and hydroxylated metabolites (ATR + MET) should be assayed. A method is presented for the analysis of these substances in serum. Method validation included the estimation of the quantitative relationship between the concentrations and the standard deviations (SD), which supports the optimal incorporation of TDM results into nonparametric pharmacokinetic models. The concentrations of the analytes were evaluated in human subjects receiving ATR. The method's performance improved by taking the sums of acid and lactone concentrations into account. The concentration-SD relationship was linear, and we recommend applying Theil's regression for estimating the assay error. All analytes could be detected by 2 h post dose in the samples of human subjects. The changes in metabolite/parent drug concentration ratios in time depended on the dose. The method is suitable for the TDM of ATR with a focus on precision pharmacotherapy.

[Therapeutic drug monitoring of atypical antipsychotics and antidepressants: conclusions of the first year at Semmelweis University].

INTRODUCTION: Pharmacotherapy supported by therapeutic drug monitoring (TDM) has a tradition in psy - chiatry. Novel diagnostic infrastructure based on mass spectrometry has been developed at Semmelweis University, allowing the renewal of psychiatric treatments supported by TDM. In a cooperation of the Department of Laboratory Medicine, and the Department of Psychiatry and Psychotherapy 13 drugs were assayed in a routine setting. Several drugs were determined with their pharmacologically active metabolites. METHODS: In 2019, 678 TDM tests were performed on samples taken from 465 patients receiving treatment at the Depart - ment of Psychiatry and Psychotherapy. No patient-related data were used for the presented evaluation. Analytical method performance was evaluated by method validation, using internal controls and participating in an inter - national external quality assessment scheme. The assay results were compared to reference ranges recommended in the leading international consensus guideline. RESULTS: Tests of clozapine, olanzapine and miscellaneous drugs comprised 35.8%, 34.9% and 29.3% of all orders, res - pec tively. A high proportion of results was outside the limits of the therapeutic ranges. Similarly, several concentra tion ratios of metabolites and parent drugs were outside the reference ranges. CONCLUSIONS: The reference ranges related to drug and metabolite concentrations are useful indicators but do not pre - sent therapeutic goals or a basis for clinical decisions by themselves. The interpretation of TDM results should be based on the condition of the patient, the clinical goals and the therapeutic context (e.g. the coadministration of other drugs), handled as an element of more complex decision making, and should serve the individualization of therapy.

Analysis of 14 drugs in dried blood microsamples in a single workflow using whole blood and serum calibrators.

Aim: Multiplexed, high-throughput analysis facilitates therapeutic drug monitoring. 14 drugs with various physico-chemical properties were quantitated in dried blood microsamples. Methods: Analytes were extracted employing eight solvent compositions and seven extraction methods. The applicability of liquid serum, dried serum and dried whole blood calibrators was investigated. Results: High recoveries were attained. Calibration using dried serum yielded lowest total error. Reducing sample hematocrit caused outstanding elevations in recovery of analytes with high polarity or affinity to erythrocytes. 9-day analyte stability was demonstrated. Conclusion: Based on the analysis of spiked samples, multiplexed testing of drugs in dried blood microsamples seems feasible, but with analyte-dependent method performance. Dried serum calibration allows the adaptation of serum-based workflows. Further evaluation using real-life specimens is needed.

Development of a methodology to make individual estimates of the precision of liquid chromatography-tandem mass spectrometry drug assay results for use in population pharmacokinetic modeling and the optimization of dosage regimens.

BACKGROUND: The clinical value of therapeutic drug monitoring can be increased most significantly by integrating assay results into clinical pharmacokinetic models for optimal dosing. The correct weighting in the modeling process is 1/variance, therefore, knowledge of the standard deviations (SD) of each measured concentration is important. Because bioanalytical methods are heteroscedastic, the concentration-SD relationship must be modeled using assay error equations (AEE). We describe a methodology of establishing AEE's for liquid chromatography-tandem mass spectrometry (LC-MS/MS) drug assays using carbamazepine, fluconazole, lamotrigine and levetiracetam as model analytes. METHODS: Following method validation, three independent experiments were conducted to develop AEE's using various least squares linear or nonlinear, and median-based linear regression techniques. SD's were determined from zero concentration to the high end of the assayed range. In each experiment, precision profiles of 6 ("small" sample sets) or 20 ("large" sample sets) out of 24 independent, spiked specimens were evaluated. Combinatorial calculations were performed to attain the most suitable regression approach. The final AEE's were developed by combining the SD's of the assay results, established in 24 specimens/spiking level and using all spiking levels, into a single precision profile. The effects of gross hyperbilirubinemia, hemolysis and lipemia as laboratory interferences were investigated. RESULTS: Precision profiles were best characterized by linear regression when 20 spiking levels, each having 24 specimens and obtained by performing 3 independent experiments, were combined. Theil's regression with the Siegel estimator was the most consistent and robust in providing acceptable agreement between measured and predicted SD's, including SD's below the lower limit of quantification. CONCLUSIONS: In the framework of precision pharmacotherapy, establishing the AEE of assayed drugs is the responsibility of the therapeutic drug monitoring service. This permits optimal dosages by providing the correct weighting factor of assay results in the development of population and individual pharmacokinetic models.