Plasma protein binding of ceftriaxone in critically ill patients: can we predict unbound fractions?

BACKGROUND: Standard antibiotic dosing is not suitable for critically ill patients, due to altered pharmacokinetics (PK) in these patients. Knowledge of protein binding is important for optimizing antibiotic exposure because only the unbound fraction is pharmacologically active. If unbound fractions can be predicted, minimal sampling techniques and less costly methods can be routinely used. METHODS: Data from the DOLPHIN trial, a prospective randomized clinical trial that included critically ill patients, were used. Total and unbound ceftriaxone concentrations were determined using a validated UPLC-MS/MS method. A non-linear saturable binding model was made using 75% of the trough concentrations and validated on the remaining data. Our model and previously published models were tested for their performance for subtherapeutic (<1 mg/L) and high (>10 mg/L) unbound concentrations. RESULTS: In total, 113 patients were sampled [Acute Physiology And Chronic Health Evaluation version 4 (APACHE IV) score 71 (IQR 55-87), albumin 28 g/L (IQR 24-32)]. This resulted in 439 samples (trough = 224, peak = 215). Unbound fractions were significantly different between samples taken at trough and peak times [10.9% (IQR 7.9-16.4) versus 19.7% (IQR 12.9-26.6), P < 0.0001], which was not explained by concentration differences. Our model and most literature models showed good sensitivity and low specificity to determine high and subtherapeutic ceftriaxone trough concentrations using only the total ceftriaxone and albumin concentrations. CONCLUSIONS: Ceftriaxone protein binding is not concentration related in critically ill patients. Existing models show good ability to predict high concentrations, but low specificity in predicting subtherapeutic concentrations.

Stability of 10 Beta-Lactam Antibiotics in Human Plasma at Different Storage Conditions.

BACKGROUND: Recently, several studies have assessed the effects of therapeutic drug monitoring of frequently prescribed beta-lactam antibiotics, for which they were quantified in human plasma samples. Beta-lactams are considered unstable, leading to extra challenges in quantification. Therefore, to ensure sample stability and minimize sample degradation before analysis, stability studies are crucial. This study investigated the stability of 10 frequently used beta-lactam antibiotics in human plasma at relevant storage conditions for clinical use. METHODS: Amoxicillin, benzylpenicillin, cefotaxime, ceftazidime, ceftriaxone, cefuroxime, flucloxacillin, imipenem, meropenem, and piperacillin were analyzed using ultraperformance convergence chromatography tandem mass spectrometry and liquid chromatography tandem mass spectrometry. Their short-term and long-term stabilities were investigated by measuring quality control samples at low and high concentrations against freshly prepared calibration standards. Measured concentrations at each time point were compared with the concentrations at T = 0. Antibiotics were considered stable if recovery results were between 85% and 115%. RESULTS: Short-term stability results indicated ceftriaxone, cefuroxime, and meropenem to be stable up to 24 hours at room temperature. All evaluated antibiotics, except imipenem, were stable on ice in a cool box for 24 hours. Amoxicillin, benzylpenicillin, and piperacillin were stable for 24 hours at 4-6°C. Cefotaxime, ceftazidime, cefuroxime, and meropenem were stable at 4-6°C up to 72 hours. Ceftriaxone and flucloxacillin were stable for 1 week at 4-6°C. Long-term stability results showed that all antibiotics were stable up to 1 year at -80°C, except imipenem and piperacillin, which were stable for 6 months at -80°C. CONCLUSIONS: Plasma samples for amoxicillin, benzylpenicillin, cefotaxime, ceftazidime, flucloxacillin, and piperacillin may be stored for a maximum of 24 hours in a cool box. Refrigeration is suitable for plasma samples of amoxicillin, benzylpenicillin, meropenem, and piperacillin for up to 24 hours and cefotaxime, ceftriaxone, ceftazidime and cefuroxime for 72 hours. Plasma samples for imipenem should be frozen directly at -80°C. For long-term storage, plasma samples can be stored at -80°C for a maximum of 6 months for imipenem and piperacillin and 12 months for all other evaluated antibiotics.

Development and Validation of a Dried Blood Spot Assay Using UHPLC-MS/MS to Identify and Quantify 12 Antihypertensive Drugs and 4 Active Metabolites: Clinical Needs and Analytical Limitations.

PURPOSE: As nonadherence to antihypertensive drugs (AHDs) can increase the risk of cardiovascular events, hospitalization, and higher costs, there is a need for a reliable, objective, and easy method to assess nonadherence in patients. The dried blood spot (DBS) sampling method used to measure drug concentrations meets these requirements. For detecting nonadherence, identification is more important than quantification. Owing to their use in clinical practice, it is important to measure multiple AHDs with a single method. Therefore, we developed and validated a single DBS method for 17 commonly used AHDs and 4 active metabolites using ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). METHODS: Analytical validation of the DBS assay was performed in accordance with the guidelines on bioanalytical method validation of the European Medicines Agency and US Food and Drug Administration as well as the International Association of Therapeutic Drug Monitoring and Clinical Toxicology guidelines. RESULTS: We validated 12 of the 17 AHDs according to the European Medicines Agency and Food and Drug Administration requirements for bioanalytical method validation. Eleven AHDs were validated for both identification and quantification of drug concentrations, whereas nifedipine was only validated for identification. However, 5 of the 17 AHDs were excluded due to suboptimal validation results. Lercanidipine was excluded due to nonlinearity, and all 4 AHDs measured in the negative mode of UHPLC-MS/MS were not in accordance with one or more of the acceptance criteria and were therefore excluded. CONCLUSIONS: The described method accurately measured AHDs in DBS and can be used to determine nonadherence in patients. However, method validation revealed a challenging balance between analytical limitations and clinical needs when analyzing multiple drugs using the same method.

Barriers and facilitators for therapeutic drug monitoring of beta-lactams and ciprofloxacin in the ICU: a nationwide cross-sectional study.

BACKGROUND: Recent studies demonstrated that failure of achieving pharmacodynamic targets of commonly used antibiotics is common in critically ill patients. Therapeutic drug monitoring (TDM) can contribute to optimize the exposure of beta-lactams and ciprofloxacin. While evidence for TDM of these antibiotics is growing, translation into clinical implementation remains limited. Therefore, perceived barriers and facilitators are important for implementing TDM in this population. The primary aim of this study was to identify healthcare professionals' barriers and facilitators for the implementation of TDM of beta-lactams and ciprofloxacin in Dutch intensive care units (ICU). METHODS: We conducted a nationwide cross-sectional online survey among healthcare professionals (HCPs) involved in antibiotic treatment of ICU patients. An adapted version of the Measurement Instrument for Determinants of Innovations was sent out. Items were considered barriers when ≥ 20% of participants responded with a negative answer. If ≥ 80% of the participants responded with a positive answer, the item was considered a facilitator. RESULTS: Sixty-four HCPs completed the survey, of which 14 were from academic hospitals, 25 from general hospitals, and 25 from teaching hospitals. Most participants were hospital pharmacists (59%) or medical specialists (23%). Eleven barriers and four facilitators for implementation of TDM of beta-lactams were identified; 17 barriers for TDM of ciprofloxacin and no facilitators. The most important barriers were a lack of conclusive evidence, organizational support, and low availability of assays. Additional barriers were a lack of consensus on which specific patients to apply TDM and which pharmacodynamic targets to use. Identified facilitators for beta-lactam TDM implementation are low complexity and high task perception, combined with the perception that TDM is important to prevent side effects and to adequately treat infections. Twenty-eight percent of participants reported that flucloxacillin could be analyzed in their hospital. Assay availability of other beta-lactams and ciprofloxacin was lower (3-17%). CONCLUSION: Several barriers were identified that could obstruct the implementation of TDM of beta-lactams and ciprofloxacin in the ICU. In particular, education, clear guidelines, and organizational support should be considered when creating tailored implementation strategies. Finally, evidence of beneficial clinical outcomes on TDM of beta-lactams and ciprofloxacin can enhance further implementation.

Clinical Pharmacokinetics of Fosfomycin after Continuous Infusion Compared with Intermittent Infusion: a Randomized Crossover Study in Healthy Volunteers.

Continuous infusion (CON) of fosfomycin has been proposed as potentially advantageous in certain clinical scenarios. However, no clinical data on the pharmacokinetics (PK) of fosfomycin after CON are available to date. This study aimed to investigate the PK of fosfomycin after CON and compare it with intermittent infusion (INT) of fosfomycin. A randomized two-way crossover study including 8 healthy male volunteers was performed. Each subject received fosfomycin as INT of 8 g over 30 min every 8 h and, separated by a washout period, as CON of 1 g/h preceded by a loading dose of 8 g over 30 min. PK sampling was performed for 18 and 24 h in the CON and INT groups, respectively. Fosfomycin was generally well tolerated. However, 2 out of 8 subjects (25%) developed thrombophlebitis at the infusion site following CON, which was prevented in the following subjects with a simultaneous coinfusion of Ringer's lactate. The steady-state maximum concentration of drug in serum (Cmax) and area under the concentration-time curve from 0 to 24 h at steady state (AUCSS,0-24) of fosfomycin after INT were 551.5 ± 67.8 mg/liter and 3,678.5 ± 601.9 h · mg/liter, respectively. CON led to an average steady-state concentration of 183.8 ± 35.9 mg/liter, resulting in a calculated AUCSS,0-24 of 4,411.2 ± 862.4 h · mg/liter, which was 1.2-fold higher than that with INT. CON resulted in a 100% T>MIC (time during which the drug concentration exceeds the MIC) for MICs of ≤128 mg/liter, whereas the %T>MIC for INT was only 44% for an MIC of 128 mg/liter. CON of fosfomycin led to improved PK and PK/pharmacodynamic (PD) determinants in plasma of healthy volunteers. The clinical relevance of these findings remains to be investigated in patients.

Clinical Validation of a Dried Blood Spot Assay for 8 Antihypertensive Drugs and 4 Active Metabolites.

BACKGROUND: Drug nonadherence is one of the major challenges faced by resistant hypertension patients, and identification of this problem is needed for optimizing pharmacotherapy. Dried blood spot (DBS) sampling is a minimally invasive method designed to detect and determine the degree of nonadherence. In this study, a DBS method for qualifying 8 antihypertensive drugs (AHDs) and 4 active metabolites was developed and validated using ultra high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). METHOD: The DBS assay was validated analytically and clinically, in accordance with FDA requirements. Analytical validation was accomplished using UHPLC-MS/MS. For clinical validation, paired peak and trough levels of DBS and plasma samples were simultaneously collected and comparatively analyzed using Deming regression and Bland-Altman analyses. All concentrations below the set lower limit were excluded. Deming regression analysis was used to predict comparison bias between the collected plasma and DBS samples, with DBS concentrations corrected accordingly. RESULTS: The UHPLC-MS/MS method for simultaneously measuring 8 AHDs and their metabolites in DBS, was successfully validated. With Deming regression no bias was observed in N = 1; constant bias was seen in N = 6 and proportional bias in N = 11 of the AHDs and metabolites. After correction for bias, only one metabolite (canrenone) met the 20% acceptance limit for quantification, after Bland-Altman analyses. In addition, amlodipine, valsartan, and [enalaprilate] met the 25% acceptance limit. CONCLUSIONS: A novel DBS assay for simultaneously qualifying and quantifying 8 AHDs and their metabolites, has been successfully developed and validated. The DBS assay is therefore a suitable method to detect drug nonadherence. However, with the exception of canrenone, the interchangeable use of plasma and DBS sampling to interpret drug quantities should be avoided.

Failure of target attainment of beta-lactam antibiotics in critically ill patients and associated risk factors: a two-center prospective study (EXPAT).

BACKGROUND: Early and appropriate antibiotic dosing is associated with improved clinical outcomes in critically ill patients, yet target attainment remains a challenge. Traditional antibiotic dosing is not suitable in critically ill patients, since these patients undergo physiological alterations that strongly affect antibiotic exposure. For beta-lactam antibiotics, the unbound plasma concentrations above at least one to four times the minimal inhibitory concentration (MIC) for 100% of the dosing interval (100%ƒT > 1-4×MIC) have been proposed as pharmacodynamic targets (PDTs) to maximize bacteriological and clinical responses. The objectives of this study are to describe the PDT attainment in critically ill patients and to identify risk factors for target non-attainment. METHODS: This prospective observational study was performed in two ICUs in the Netherlands. We enrolled adult patients treated with the following beta-lactam antibiotics: amoxicillin (with or without clavulanic acid), cefotaxime, ceftazidime, ceftriaxone, cefuroxime, and meropenem. Based on five samples within a dosing interval at day 2 of therapy, the time unbound concentrations above the epidemiological cut-off (ƒT > MICECOFF and ƒT > 4×MICECOFF) were determined. Secondary endpoints were estimated multivariate binomial and binary logistic regression models, for examining the association of PDT attainment with patient characteristics and clinical outcomes. RESULTS: A total of 147 patients were included, of whom 63.3% achieved PDT of 100%ƒT > MICECOFF and 36.7% achieved 100%ƒT > 4×MICECOFF. Regression analysis identified male gender, estimated glomerular filtration rate (eGFR) ≥ 90 mL/min/1.73 m2, and high body mass index (BMI) as risk factors for target non-attainment. Use of continuous renal replacement therapy (CRRT) and high serum urea significantly increased the probability of target attainment. In addition, we found a significant association between the 100%ƒT > MICECOFF target attainment and ICU length of stay (LOS), but no significant correlation was found for the 30-day survival. CONCLUSIONS: Traditional beta-lactam dosing results in low target attainment in the majority of critically ill patients. Male gender, high BMI, and high eGFR were significant risk factors for target non-attainment. These predictors, together with therapeutic drug monitoring, may help ICU clinicians in optimizing beta-lactam dosing in critically ill patients. TRIAL REGISTRATION: Netherlands Trial Registry (EXPAT trial), NTR 5632 . Registered on 7 December 2015.

Simultaneous quantification of ambrisentan, macitentan and sitaxentan in human plasma using UPLC-MS/MS.

Endothelin receptor antagonists (ERAs) such as, ambrisentan, macitentan and sitaxentan are primarily used for the treatment of pulmonary arterial hypertension. Considering the rise in endothelin in pre-eclampsia, ERAs may also be useful in its treatment. To evaluate the pharmacokinetics of ERAs, a rapid ultra-performance liquid chromatography tandem mass spectrometry method was developed and validated to determine the concentration of ambrisentan, macitentan and sitaxentan in human plasma. Plasma samples were treated with methanol to induce protein precipitation. A chromatographic separation was performed on a C18 column using a gradient of methanol-water containing 0.1% formic acid and 0.013% ammonium acetate and a flow rate of 0.5 ml/min. Multiple reaction monitoring was used for quantification. This method was validated in a linear range of 20.28-2028 µg/l for ambrisentan, 4.052-405.2 µg/l for macitentan and 205.4-10 270 µg/l for sitaxentan. The method was successfully validated according to US Food and Drug Administration guidelines to determine the concentrations of macitentan, ambrisentan and sitaxentan in human plasma. This method is now being used for study samples and clinical patient samples.

Highly sensitive and rapid determination of tacrolimus in peripheral blood mononuclear cells by liquid chromatography-tandem mass spectrometry.

After solid organ transplantation, tacrolimus is given to prevent rejection. Therapeutic drug monitoring is used to reach target concentrations of tacrolimus in whole blood. Because the site of action of tacrolimus is the lymphocyte, and tacrolimus binds ~80% to erythrocytes, the intracellular tacrolimus concentration in lymphocytes is possibly more relevant. For this purpose, we aimed to develop, improve and validate a UPLC-MS/MS method to measure tacrolimus concentrations in isolated peripheral blood mononuclear cells (PBMCs). PBMCs were isolated using a Ficoll separation technique, followed by a washing step using red blood cell lysis. A cell suspension of 50 µL containing 1 million PBMCs was used in combination with MagSiMUS-TDMPREP . To each sample we added 30 µL lysis buffer, 20 µL reconstitution buffer containing 13 C2 H4 -tacrolimus as internal standard, 40 µL MagSiMUS-TDMPREP Type I Particle Mix and 175 µL Organic Precipitation Reagent VI for methanol-based protein precipitation. A 10 µL aliquot of the supernatant was injected into the UPLC-MS/MS system. The method was validated, resulting in high sensitivity and specificity. The method was linear (r2  = 0.997) over the range 5.0-1250 pg/1 × 106 PBMCs. The inaccuracy was <5% and the imprecision was <15%. The washing steps following Ficoll isolation could be performed at either room temperature or on ice, with no effect of the temperature on the results. A method for the analysis of tacrolimus concentrations in PBMCs was developed and successfully validated. Further research will be performed to investigate the correlation between concentrations in PBMCs and clinical outcome.

Therapeutic Drug Monitoring to Assess Drug Adherence in Assumed Resistant Hypertension: A Comparison With Directly Observed Therapy in 3 Nonadherent Patients.

Resistant hypertension is a common health problem leading to suboptimal cardiovascular prevention. A large number of patients with resistant hypertension have poor medication adherence explaining their assumed resistance to therapy. We combined directly observed therapy (DOT) with therapeutic drug monitoring (TDM) in 3 patients at several time points to enable an extensive feedback on blood pressure (BP) and drug levels. BP was measured with an automatic oscillatory device at regular intervals of 5 minutes (directly before and after drug intake) and at 30-minute intervals (at night) during admission. Blood samples were obtained at different time points (t = in hours; t = 0, 2, 4, 6, 12, and 24 hours after drug intake). DOT was performed under supervision of the physician. In 2 of the 3 patients, automated BP decreased directly after DOT, -10/0 and -5/-5 mm Hg, respectively. Plasma drug levels for several drugs or active metabolites were 0 at t = 0, whereas plasma levels were positive at t = 24 hours after observed intake. We recommend a more frequent use of TDM combined with repeated BP measurements in clinical practice because this is a convenient, objective method of measurement and to ensure that actual drug levels reflect the BP at the time of measurement.

Quantification of Phosphatidylethanols in Whole Blood as a Proxy for Chronic Alcohol Consumption, Using Ultra Performance Convergence Chromatography Tandem Mass Spectrometry.

BACKGROUND: Detection of alcohol consumption after a longer period can be useful in certain patient groups. To monitor chronic alcohol consumption, a novel analytical method for the quantification of phosphatidylethanols (PEths) was developed and validated using ultra performance convergence chromatography-tandem mass spectrometry. METHODS: The main phosphatidylethanols like palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanol (POPEth), 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphoethanol, and 1,2-dioleoyl-sn-glycero-3-phosphoethanol were analyzed using a simple and fast sample preparation protocol followed by chromatographic separation using ultra performance convergence chromatography, a novel kind of supercritical fluid chromatography. Mass spectrometric detection was conducted by applying negative electrospray ionization and multiple reaction monitoring mode. Only 50 µL of whole blood is needed for the simultaneous quantification of all 3 compounds within 5-minute run-to-run analysis time. POPEth-d5 was applied as internal standard. RESULTS: The method was validated according to the Food and Drug Administration guidelines. Correlation coefficients were higher than 0.995 for all 3 compounds. Intraday and interday inaccuracies were <15% for all analytes in the established linear range. Intraday and interday imprecision were <15% for all analytes. Lower limit of quantification for 1,2-dioleoyl-sn-glycero-3-phosphoethanol, palmitoyl-2-linoleoyl-sn-glycero-3-phosphoethanol, and POPEth are, respectively, 3, 6, and 6 mcg/L. Sample stability at -80°C was 1 year. Extracts were stable for 1 day in the autosampler and 2 days at 2-8°C in a closed Eppendorf tube. Samples were tested after 3 freeze-thaw cycles and considered stable. Patient samples have been analyzed with this new method. In a cohort of 248 pregnant women, 17 patients (6.9%) scored positive for PEth. CONCLUSIONS: The described method is suitable for the simultaneous quantitative analysis of the most abundant PEth homologues. Major advantages are low LLOQs, minimal sample volume and clean-up, and a short run time. The method is now available to monitor alcohol consumption in patients and has been incorporated in clinical practice and research.

Dried Blood Spot Analysis for Therapeutic Drug Monitoring of Antipsychotics: Drawbacks of Its Clinical Application.

BACKGROUND: Dried blood spot (DBS) sampling offers a minimally invasive sampling method for therapeutic drug monitoring of antipsychotics. To facilitate implementation in clinical practice, the aim of this study was to perform a clinical validation study of a DBS method for quantification of risperidone, aripiprazole, pipamperone, and their major metabolites 9-OH risperidone and dehydro-aripiprazole in a real-life, clinical setting. METHODS: Paired DBS and venous plasma samples were analyzed (n = 35 for risperidone, n = 21 for aripiprazole, n = 21 for pipamperone). Estimated plasma concentrations were calculated from DBS concentrations based on hematocrit and/or Deming regression formulas. Deming regression and Bland-Altman analyses were used to determine the agreement between the calculated and measured plasma concentrations. For Bland-Altman analysis, the following acceptance limit was used: for a minimum of 67% of the samples, the difference of the 2 measurements should be within 20% of their mean. RESULTS: The median venous plasma levels were 0.9 mcg/L for risperidone, 14.8 mcg/L for 9-OH risperidone, 135.4 mcg/L for aripiprazole, 54.9 mcg/L for dehydro-aripiprazole, and 56.4 mcg/L for pipamperone. All antipsychotics required different correction formulas of DBS concentrations for best agreement. Subsequently, no constant or proportional bias was observed using Deming regression analysis. With Bland-Altman analyses, for risperidone, 45% of the samples were within the 20% limits; for 9-OH risperidone, 36%; for aripiprazole, 45%; for dehydro-aripiprazole, 35%; and for pipamperone, 43%. CONCLUSIONS: The DBS method to quantify risperidone, aripiprazole, pipamperone, and their major metabolites did not meet the acceptance criteria in the Bland-Altman analyses. Therefore, this DBS method was not clinically valid. This study shows the importance of a clinical validation study with use of Bland-Altman plots before clinical implementation.

Simultaneous quantification of fentanyl, sufentanil, cefazolin, doxapram and keto-doxapram in plasma using liquid chromatography-tandem mass spectrometry.

A simple and specific UPLC-MS/MS method was developed and validated for simultaneous quantification of fentanyl, sufentanil, cefazolin, doxapram and its active metabolite keto-doxapram. The internal standard was fentanyl-d5 for all analytes. Chromatographic separation was achieved with a reversed-phase Acquity UPLC HSS T3 column with a run-time of only 5.0 min per injected sample. Gradient elution was performed with a mobile phase consisting of ammonium acetate or formic acid in Milli-Q ultrapure water or in methanol with a total flow rate of 0.4 mL min-1 . A plasma volume of only 50 µL was required to achieve adequate accuracy and precision. Calibration curves of all five analytes were linear. All analytes were stable for at least 48 h in the autosampler. The method was validated according to US Food and Drug Administration guidelines. This method allows quantification of fentanyl, sufentanil, cefazolin, doxapram and keto-doxapram, which is useful for research as well as therapeutic drug monitoring, if applicable. The strength of this method is the combination of a small sample volume, a short run-time, a deuterated internal standard, an easy sample preparation method and the ability to simultaneously quantify all analytes in one run.

Dried blood spot analysis for the quantification of vancomycin and creatinine using liquid chromatography - tandem mass spectrometry: Method development and validation.

BACKGROUND: Vancomycin is a widely used antibiotic for the treatment of gram-positive bacterial infections, especially for methicillin-resistant Staphylococcus aureus (MRSA) infections. Due to a small therapeutic range and large inter-patient variability, therapeutic drug monitoring (TDM) of vancomycin is required to minimize toxicity and maximize treatment efficacy. Venous blood sampling is mostly applied for TDM of vancomycin, although this widely used sampling method is more invasive compared to less painful alternatives, such as the dried blood spot (DBS) method, which can be performed at home. METHOD: We developed an UPLC-MS/MS method for the quantification of vancomycin and creatinine in DBS. A fast sample preparation and short analysis run time of 5.2 min were applied, which makes this method highly suitable for clinical settings. Validation was performed according to international (FDA and EMA) guidelines. RESULTS: The validated concentration range was found linear for creatinine from 41.8 µmol/L to 722 µmol/L and for vancomycin from 3.8 mg/L to 76.6 mg/L (r2 > 0.990) and the inaccuracies, imprecisions, hematocrit effects, and recoveries were < 15 % for both compounds. No significant carryover effect was observed. CONCLUSION: Hence, we successfully validated a quantification method for the simultaneous determination of creatinine and vancomycin in DBS.

Monitoring antihypertensive drug concentrations to determine nonadherence in hypertensive patients with or without a kidney transplant.

BACKGROUND: Nonadherence to antihypertensive drugs (AHDs) is a major contributor to pseudo-resistant hypertension. The primary objective of this study was to determine the prevalence of nonadherence to AHDs among patients visiting the nephrology and vascular outpatient clinics. METHODS: Patients were eligible to participate in this prospective observational study if they used at least two AHDs that could be measured with a validated UHPLC-MS/MS method and had an office blood pressure at least 140 and/or at least 90 mmHg. For resistant hypertension, included patients had to use at least three AHDs including a diuretic or four AHDs. Adherence was assessed by measuring drug concentrations in blood. The complete absence of drug in blood was defined as nonadherence. A posthoc analysis was performed to determine the influence of a having a kidney transplant on the adherence rates. RESULTS: One hundred and forty-two patients were included of whom 66 patients fulfilled the definition of resistant hypertension. The overall adherence rate to AHDs was 78.2% ( n  = 111 patients), with the highest adherence rate for irbesartan (100%, n  = 9) and lowest adherence rate for bumetanide ( n  = 69%, n  = 13). In further analysis, only kidney transplantation could be identified as an important factor for adherence (adjusted odds ratio = 3.35; 95% confidence interval 1.23-9.09). A posthoc analysis showed that patients with a kidney transplant were more likely to be adherent to AHDs (non-KT cohort 64.0% vs. KT-cohort 85.7%, χ 2 (2) = 10.34, P  = 0.006). CONCLUSION: The adherence rate to AHDs in hypertensive patients was high (78.2%) and even higher after a kidney transplant (85.7%). Furthermore, patients after kidney transplant had a lower risk of being nonadherent to AHDs.

High-throughput analysis for the simultaneous quantification of nine beta-lactam antibiotics in human plasma by UPC2-MS/MS: Method development, validation, and clinical application.

Quantification of beta-lactam antibiotics can be performed by using liquid chromatography in combination with tandem mass spectrometry (MS/MS) or ultraviolet (UV) detection. Since beta-lactam antibiotics are known as highly polar analytes, using standard reversed phase chromatography will result in very early elution, which is often not desirable. Some retention is preferred to reduce matrix effects, because a high amount of non-retained molecular matrix species elute early from the column. For highly polar analytes, ultra-performance convergence chromatography (UPC2) may be a suitable alternative. This method is based on supercritical fluid chromatography. To our knowledge, we developed the first UPC2-MS/MS method for the determination of amoxicillin, benzylpenicillin, flucloxacillin, piperacillin, cefotaxime, cefuroxime, ceftazidime, imipenem, meropenem, and the free fraction of cefuroxime and flucloxacillin in human plasma. The method was validated according to the Food and Drug Administration guidelines. The method was found linear (r2 >0.990) for all analytes. The inaccuracies and imprecisions were < 15% for all analytes. The matrix effect and recovery were nearly all consistent with coefficient of variation of less than 15% and no significant carryover effect was observed. Furthermore, this method was found to be suitable for daily routine analysis in hospital settings, requiring only 50 µL of plasma. This novel, sensitive, and specific UPC2-MS/MS method demonstrated its value in the analysis of a more than 800 human plasma samples in a clinical trial using simple and fast sample preparation and short analysis run time of only 5 min.

Evaluation of the importance of mixing during preparation of antibiotic infusions.

BACKGROUND: The mixing step after medication addition to the infusion bag is frequently omitted during the preparation of drug infusions. However, the importance of mixing when preparing antibiotic infusions is still unknown. METHODS: The primary aim of this study was to assess the importance of the mixing step by comparing the concentrations of unmixed antibiotic infusions (cefuroxime, flucloxacillin, meropenem, and vancomycin) with the declared concentration at regular intervals during infusion. The secondary aim was to compare concentrations between preparation sites (hospital pharmacy versus clinical ward). Infusion bags were run through electronic infusion pumps. For cefuroxime, flucloxacillin, and meropenem, samples were collected 1, 15, and 20 min after starting the administration (infusion duration: 30 min). For vancomycin, samples were collected after 1, 60, and 110 min (infusion duration: 120 min). Vancomycin concentrations were measured using the Architect c4000 analyser and other concentrations using a validated UPC2-MS-MS multimethod. RESULTS: The median concentrations of the four antibiotics were comparable to the declared concentration at all three time points. No significant differences were found between preparation sites. CONCLUSIONS: Spontaneous mixing occurred in the examined antibiotic solutions during normal handling.

Pipamperone Population Pharmacokinetics Related to Effectiveness and Side Effects in Children and Adolescents.

BACKGROUND: Pipamperone is a frequently prescribed antipsychotic in children and adolescents in the Netherlands, Belgium, and Germany. However, pediatric pharmacokinetics and the relationship with side effects and efficacy are unknown. Currently, divergent pediatric dosing recommendations exist. OBJECTIVES: The objective of this study was to describe the population pharmacokinetics of pipamperone in children and adolescents; to correlate measured and predicted pipamperone trough concentrations and predicted 24-h area under the curves with effectiveness, extrapyramidal symptoms, and sedation; and to propose dose recommendations based on simulations. METHODS: Pipamperone concentrations were collected from Dutch pediatric patients in a prospective naturalistic trial (n = 8), and German pediatric patients in a therapeutic drug monitoring service (n = 22). A total of 70 pipamperone concentrations were used to develop a population pharmacokinetic model with non-linear mixed-effects modeling (NONMEM®). Additionally, an additional random sample of 21 German patients with 33 pipamperone concentrations from the same therapeutic drug monitoring service was used for external validation. Pharmacokinetic parameters were related to clinical improvement, sedation, and extrapyramidal symptoms. Simulations were performed to determine optimal dosages. RESULTS: In a one-compartment model, the apparent volume of distribution was 416 L/70 kg and the apparent clearance was 22.1 L/h/70 kg. Allometric scaling was used to correct for differences in bodyweight. The model was successfully externally validated. The median [25th-75th percentile] measured pipamperone trough concentrations were numerically higher in responders (98.0 µg/L [56.0-180.5 µg/L]) than in non-responders (58.0 µg/L [14.9-105.5 µg/L]), although non-significant (p = 0.14). A twice-daily 0.6-mg/kg dosage was better than a fixed dosage to attain the concentration range observed in responders. CONCLUSIONS: Our findings suggest that pipamperone therapeutic reference ranges may be lower for children with behavioral problems than recommended for adults with psychotic symptoms (100-400 µg/L). When dosing pipamperone in children and adolescents, bodyweight should be taken into account.

Drug nonadherence is a common but often overlooked cause of hypertensive urgency and emergency at the emergency department.

OBJECTIVES: Over 70% of patients who visit the emergency department with a hypertensive emergency or a hypertensive urgency have previously been diagnosed with hypertension. Drug nonadherence is assumed to play an important role in development of hypertensive urgency and hypertensive emergency, but exact numbers are lacking. We aimed to retrospectively compare characteristics of patients with hypertensive urgency and hypertensive emergency and to prospectively quantify the attribution of drug nonadherence. METHODS: We retrospectively analysed clinical data including information on nonadherence obtained by treating physicians of patients with SBP at least 180 mmHg and DBP at least 110 mmHg visiting the emergency department between 2012 and 2015. We prospectively studied drug adherence among patients admitted to the emergency department with severely elevated BP by measuring plasma drug levels using liquid chromatography tandem mass spectrometry from September 2016 to March 2017. RESULTS: Of the 1163 patients retrospectively analysed, 257 (22.0%) met the criteria for hypertensive urgency and 356 (30.6%) for hypertensive emergency. Mean SBP (SD) was 203 (19) mmHg and mean DBP 121 (12) mmHg. Mean age was 60.1 (14.6) years; 55.1% were men. In 6.3% of patients with hypertensive urgency or hypertensive emergency, nonadherence was recorded as an attributing factor. Of the 59 patients prospectively analysed, 18 (30.5%) were nonadherent for at least one of the prescribed antihypertensive drugs. CONCLUSION: Hypertensive urgency and hypertensive emergency are common health problems resulting in frequent emergency department admissions. Workup of patients with a hypertensive urgency or hypertensive emergency should include an assessment of drug adherence to optimize treatment strategy.