The effect of renal impairment and obesity on anti-Xa peak and trough levels in patients receiving therapeutic doses of nadroparin: a comparison with control patients.

PURPOSE: Anti-Xa peak level monitoring is recommended during LMWH treatment in renal impairment or obesity. The trough level has been proposed as marker for bleeding. We studied the influence of renal impairment and obesity on anti-Xa levels. METHODS: Peak and trough levels were collected during therapeutic nadroparin treatment in patients with renal impairment, obese patients, and controls. 27 patients (n = 68 samples) were evaluated and combined with published data (n = 319 samples from 35 patients) using population pharmacokinetic (popPK) modelling. RESULTS: Median peak level was 0.44 and 0.95 IU/mL in renal impairment with and without dose reduction and 0.60 and 0.43 IU/mL in obesity and controls, respectively. Trough levels were < 0.5 IU/mL in all patients with renal impairment with dose reduction and in 5/6 control patients. In the popPK model, total body weight and eGFR were covariates for clearance and lean body weight for distribution volume. Model-based evaluations demonstrated peak levels below the therapeutic window in controls and increased levels in renal impairment. Dose reductions resulted in a different effect on peak and trough levels. Obese patients (BMI up to 32 kg/m2) had similar levels upon weight-based dosing. CONCLUSION: In renal impairment, anti-Xa peak levels after dose reduction are comparable to those in controls. Weight-based dosing is suitable for obese patients. Aiming for peak levels between 0.6 and 1.0 IU/mL in these patients would result in overexposure compared to controls. Considering the association of trough levels and bleeding risk and our findings, trough monitoring seems to be a suitable parameter to identify nadroparin accumulation.

Critical appraisal of evidence for anti-Xa monitoring and dosing of low-molecular-weight heparin in renal insufficiency.

INTRODUCTION: Several guidelines advise to monitor therapeutic LMWH therapy with peak anti-Xa concentrations in renal insufficiency with subsequent dose adjustments. A better understanding of the clinical association between peak anti-Xa concentrations and clinical outcomes is mandatory, because misunderstanding this association could lead to erroneous, and potentially even harmful, LMWH dose adjustments. AREAS COVERED: We reviewed the evidence of the widely applied therapeutic window for anti-Xa peak concentrations and report on the evidence for pharmacokinetic dose reduction in renal insufficiency, limitations of peak and trough anti-Xa concentration monitoring. EXPERT OPINION: The added value of peak anti-Xa monitoring in patients with renal insufficiency, receiving a dose reduced for pharmacokinetic changes, is not supported by data. Enoxaparin and nadroparin should be adjusted to 50-65% and 75-85% of the original dose for patients with a creatinine clearance (CrCL) of <30 ml/min and 30-60 ml/min, respectively. Tinzaparin should be adjusted to around 50% of the original dose for patients with a CrCL of <30 ml/min. In case anti-Xa monitoring is applied, trough concentration anti-Xa monitoring is preferred over peak monitoring, aiming at a maximum concentration of 0.4 IU/mL for once-daily dosed tinzaparin and 0.5 IU/mL for twice-daily dosed enoxaparin and nadroparin.

Chloroquine-induced QTc prolongation in COVID-19 patients.

BACKGROUND: In the battle against the SARS-CoV­2 pandemic, chloroquine has emerged as a new potential therapeutic option for the treatment of infected patients. A safety consideration for the application of chloroquine is its QTc-prolonging potential. Thus far, no data are available on the QTc-prolonging potential of chloroquine in COVID-19 patients. OBJECTIVE: To assess the degree of chloroquine-induced QTc prolongation in hospitalised COVID-19 patients. METHODS: A baseline electrocardiogram (ECG) and ECGs recorded during chloroquine treatment were retrospectively collected in patients suspected of having COVID-19. The QTc interval was calculated by computerised and manual interpretation. Baseline and follow-up QTc intervals were compared using the paired samples t-test. RESULTS: A total of 95 patients had a baseline ECG recording and at least one ECG recording during chloroquine therapy. Chloroquine treatment resulted in a mean QTc prolongation of 35 ms (95% CI 28-43 ms) using computerised interpretation and 34 ms (95% CI 25-43 ms) using manual interpretation. No torsade de pointes was observed during chloroquine treatment. After manual review, 22 patients (23%) had a QTc interval exceeding 500 ms during chloroquine treatment. None of these patients had a prolonged QTc interval prior to the initiation of chloroquine treatment. CONCLUSIONS: Chloroquine significantly prolongs the QTc interval in a clinically relevant matter. This highlights the need for ECG monitoring when prescribing chloroquine to COVID-19 patients.

Use of oral immunosuppressive drugs in the treatment of atopic dermatitis in the Netherlands.

BACKGROUND: Although atopic dermatitis (AD) is a very common skin disease, data on the percentage of patients with really difficult-to-treat AD are scarce. From socio-economic perspective, it is important to have more insight into these numbers, as new very effective, but expensive, treatment options will be available in the near future for difficult-to-treat AD. Estimating the number of patients with AD using oral immunosuppressive drugs can give an impression of the percentage of difficult-to-treat patients in the total AD population. OBJECTIVE: To give an overview of the use of oral immunosuppressive drugs in patients with AD in the Netherlands. METHODS: Prescription data of oral immunosuppressive drugs in the Netherlands were extracted from a pharmaceutical database (NControl) containing data of 557 million prescriptions and 7.2 million patients. An algorithm, based on the WHO Anatomical Therapeutic Chemical (ATC) codes, was used to identify patients with AD. The prescription of oral immunosuppressive drugs in patients with AD between 1 January 2012 and 1 January 2017 was evaluated. RESULTS: Based on the algorithm, 65 943 patients with AD were selected. 943 patients with AD (1.4%) used cyclosporine A, methotrexate, azathioprine or mycophenolic acid. Methotrexate was most commonly used, followed by azathioprine and cyclosporine A. A switch in medication was rarely seen. In the evaluation period, a decrease in the prescription of cyclosporine A was seen, together with an increase in the prescription of methotrexate. In 31% of the patients who stopped treatment, the discontinuation took place within the first months of treatment. CONCLUSION: In this study population, 1.4% of the patients with AD used oral immunosuppressive drugs for their eczema in a 5-year period. Methotrexate was the most commonly used systemic drug in the Netherlands for the treatment of AD.

Thiopurine metabolite levels in patients with atopic dermatitis and/or chronic hand/foot eczema treated with azathioprine.

BACKGROUND: Azathioprine is frequently used in severe eczema. It is converted in the liver into active metabolites, including 6-thioguanine nucleotide (6-TGN) and methylated 6-methylmercaptopurine (6-MMP). In the past, the therapeutic potential of azathioprine may have not been fully utilized. Recent investigations on inflammatory bowel disease have led to a better understanding of azathioprine metabolism and optimizing treatment. OBJECTIVE: To investigate whether measuring thiopurine metabolites in circulation can improve the effectiveness and safety of azathioprine treatment in patients with atopic dermatitis and/or chronic hand/foot eczema. METHODS: Azathioprine metabolite levels were measured in eczema patients during maintenance treatment (Part I) and dose escalation (Part II). Clinical effectiveness, hepatotoxicity, and bone marrow suppression were analyzed and TPMT genotype was assessed. RESULTS: A wide variation in metabolite levels in all dose groups was observed. In Part I (32 patients), there were no significant differences in 6-TGN levels between clinical responders and non-responders (p = .806). No hepatoxicity or myelotoxicity was observed. In Part II, all 6-TGN and 6-MMP levels increased during dose escalation. Hypermethylation was observed in 2/8 patients. CONCLUSION: For individual eczema patients treated with azathioprine, routinely measuring 6-TGN and 6-MMP can be helpful in optimizing azathioprine dose, improving clinical effectiveness, and preventing side effects.

Epidemiology, pathophysiology and putative genetic basis of carbamazepine- and oxcarbazepine-induced hyponatremia.

The use of carbamazepine (CBZ) and oxcarbazepine (OXC) as first-line antiepileptic drugs in the treatment of focal epilepsy is limited by hyponatremia, a known adverse effect. Hyponatremia occurs in up to half of people taking CBZ or OXC and, although often assumed to be asymptomatic, it can lead to symptoms ranging from unsteadiness and mild confusion to seizures and coma. Hyponatremia is probably due to the antidiuretic properties of CBZ and OXC that are, at least partly, explained by stimulation of the vasopressin 2 receptor/aquaporin 2 pathway. No known genetic risk variants for CBZ- and OXC-induced hyponatremia exist, but likely candidate genes are part of the vasopressin water reabsorption pathway.

Rapid target allopurinol concentrations in the hypoxic fetus after maternal administration during labour.

OBJECTIVE: Perinatal hypoxia-induced free radical formation is an important cause of hypoxic-ischaemic encephalopathy and subsequent neurodevelopmental disabilities. Allopurinol reduces the formation of free radicals, which potentially limits hypoxia-induced brain damage. We investigated placental transfer and safety of allopurinol after maternal allopurinol treatment during labour to evaluate its potential role as a neuroprotective agent in suspected fetal hypoxia. DESIGN: We used data from a randomised, double-blind multicentre trial comparing maternal allopurinol versus placebo in case of imminent fetal hypoxia (NCT00189007). PATIENTS: We studied 58 women in labour at term, with suspected fetal hypoxia prompting immediate delivery, in the intervention arm of the study. SETTING: Delivery rooms of 11 Dutch hospitals. INTERVENTION: 500 mg allopurinol, intravenously to the mother, immediately prior to delivery. MAIN OUTCOME MEASURES: Drug disposition (maternal plasma concentrations, cord blood concentrations) and drug safety (maternal and fetal adverse events). RESULTS: Within 5 min after the end of maternal allopurinol infusion, target plasma concentrations of allopurinol of ≥2 mg/L were present in cord blood. Of all analysed cord blood samples, 95% (52/55) had a target allopurinol plasma concentration at the moment of delivery. No adverse events were observed in the neonates. Two mothers had a red and/or painful arm during infusion. CONCLUSIONS: A dose of 500 mg intravenous allopurinol rapidly crosses the placenta and provides target concentrations in 95% of the fetuses at the moment of delivery, which makes it potentially useful as a neuroprotective agent in perinatology with very little side effects. TRIAL REGISTRATION: The study is registered in the Dutch Trial Register (NTR1383) and the Clinical Trials protocol registration system (NCT00189007).

Pharmacokinetics and clinical efficacy of phenobarbital in asphyxiated newborns treated with hypothermia: a thermopharmacological approach.

BACKGROUND AND OBJECTIVES: Therapeutic hypothermia can influence the pharmacokinetics and pharmacodynamics of drugs, the discipline which is called thermopharmacology. We studied the effect of therapeutic hypothermia on the pharmacokinetics of phenobarbital in asphyxiated neonates, and the clinical efficacy and the effect of phenobarbital on the continuous amplitude-integrated electroencephalography (aEEG) in a prospective study. PATIENTS AND METHODS: Data were obtained from the prospective SHIVER study, performed in two of the ten Dutch level III neonatal intensive care units. Phenobarbital data were collected between 2008 and 2010. Newborns were eligible for inclusion if they had a gestational age of at least 36 weeks and presented with perinatal asphyxia and encephalopathy. According to protocol in both hospitals an intravenous (repeated) loading dose of phenobarbital 20 mg/kg divided in 1-2 doses was administered if seizures occurred or were suspected before or during the hypothermic phase. Phenobarbital plasma concentrations were measured in plasma using a fluorescence polarization immunoassay. aEEG was monitored continuously. RESULTS AND CONCLUSION: A one-compartmental population pharmacokinetic/pharmacodynamic model was developed using a multi-level Markov transition model. No (clinically relevant) effect of moderate therapeutic hypothermia on phenobarbital pharmacokinetics could be identified. The observed responsiveness was 66%. While we still advise an initial loading dose of 20 mg/kg, clinicians should not be reluctant to administer an additional dose of 10-20 mg/kg. An additional dose should be given before switching to a second-line anticonvulsant drug. Based on our pharmacokinetic/pharmacodynamic model, administration of phenobarbital under hypothermia seems to reduce the transition rate from a continuous normal voltage (CNV) to discontinuous normal voltage aEEG background level in hypothermic asphyxiated newborns, which may be attributed to the additional neuroprotection of phenobarbital in infants with a CNV pattern.

Quantitative determination of oseltamivir and oseltamivir carboxylate in human fluoride EDTA plasma including the ex vivo stability using high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

Oseltamivir, the ethyl ester prodrug of the neuramidase inhibitor oseltamivir carboxylate, is licensed for the treatment of patients with influenza virus infection. Here we describe the development and validation of an assay for the simultaneous quantification of oseltamivir and oseltamivir carboxylate in human fluoride EDTA plasma including the ex vivo stability using liquid chromatography coupled to tandem mass spectrometry. Sample pretreatment consisted of protein precipitation with 8% (v/v) trichloroacetic acid in water using only 50 µL plasma. Chromatographic separation was performed on a reversed phase C18 column (150 mm × 2.0 mm ID, particle size 4 µm) with a stepwise gradient using 0.1% formic acid and methanol at a flow rate of 250 µL/min. A triple quadrupole mass spectrometer operating in the positive ionization mode was used for detection and drug quantification. The method was validated over a range of 3-300 ng/mL for oseltamivir and 10-10,000 ng/mL for oseltamivir carboxylate. Deuterated oseltamivir and oseltamivir carboxylate were used as internal standards. The intra-assay accuracies and precisions for oseltamivir were between -8.8 and 16.3% at the LLOQ level, whereas for all other concentration levels this was -8.6 and 14.5%. For oseltamivir carboxylate the intra-assay accuracies and precisions were between -10.9 and 10.7% at all levels. Furthermore, oseltamivir was stable in plasma and whole blood ex vivo in commercially available fluoride EDTA tubes for at least 24h at 2-8 °C. This method is now applied for the determination of both compounds in specific patient populations to evaluate current dosing guidelines.

Easy and fast LC-MS/MS determination of lidocaine and MEGX in plasma for therapeutic drug monitoring in neonates with seizures.

A fast liquid chromatography-tandem mass spectrometry with electrospray ionization method was developed and validated for simultaneous quantification of lidocaine and its active metabolite MEGX in 10 µL of plasma of neonates with seizures. The sample preparation consists of an easy protein precipitation sample pre-treatment with methanol. Chromatographic separation was achieved on a Alltima HP C18-EPS 150 mm×2.1mm column with an isocratic mobile phase of 0.1% (v/v) ammonium acetate in purified water-0.1% (v/v) formic acid in acetonitrile (70:30, v/v). The analytes were detected with a Thermo Scientific triple quadrupole Quantum Access with positive ionization. Ions monitored in the selected reaction monitoring (SRM) mode were m/z 235.2→86.6 for lidocaine (at 3.35 min), m/z 207.1→58.8 for MEGX (at 2.75 min) and 280.1→86.7 for 3-nitrolidocaine (internal standard, at 3.20 min). The method was validated over a linear range of 0.2-18.0mg/L for lidocaine and MEGX, using 3-nitrolidocaine as the internal standard. The lower limit of quantification (LLQ) was 0.2mg/L for lidocaine and MEGX. The within-run and between-run CV (%) were lower than 6.9% for both lidocaine and MEGX. Recoveries were in the range of 99.4% to 103.6%. Observed LC-MS/MS matrix effects were -6.2% for MEGX (ion suppression) and were negligible for lidocaine and the internal standard (i.e. <0.1%). Compared to other bioanalytical articles published in medical literature (PubMed) during the last 15 years that described LC-MS/MS methods for quantification of lidocaine in human plasma, our method uses less plasma, has a shorter and more simple sample pre-treatment and has a short run time.