Study on warfarin plasma concentration and its correlation with international normalized ratio

Determination of warfarin in volumetric absorptive microsampling by liquid chromatography-tandem mass spectrometry

Objective

This study aims to develop and validate bioanalytical method for quantifying warfarin in VAMS samples using liquid chromatography tandem mass spectrometry (LC-MS/MS), directly implementing the method to patients receiving warfarin therapy.

Methods

The UPLC-MS/MS method was developed and optimized, with quercetin as the internal standard. Sample preparation was carried out using protein precipitation with methanol-acetonitrile (1:3 v/v).

Results

Chromatographic separation was achieved using Acquity® UPLC BEH C18 column with 0.1 % formic acid-acetonitrile-methanol (30:69:1 v/v) as mobile phase, in isocratic elution. Multiple Reaction Monitoring (MRM) detection was done using m/z values of 307.10 → 161.06 for warfarin and 301.03 → 150.98 for quercetin as internal standard, using Electrospray Ionization (ESI) negative ion source. The clinical application of the bioanalytical method was carried out on 25 patients receiving warfarin therapy at Universitas Indonesia Hospital and warfarin levels were well within the calibration range from 6.05 to 431.39 ng/mL.

Conclusion

A novel method has been developed to analyze warfarin in VAMS samples. This method has been fully validated according to guideline from FDA 2022 and is linear in the range of 5-500 ng/mL and the value of r ≥ 0.9977, and successfully applied for the analysis of warfarin in VAMS samples of clinical patients.

Potential Clinically Relevant Effects of Sialylation on Human Serum AAG-Drug Interactions Assessed by Isothermal Titration Calorimetry: Insight into Pharmacoglycomics?

Human serum alpha-1 acid glycoprotein is an acute-phase plasma protein involved in the binding and transport of many drugs, especially basic and lipophilic substances. It has been reported that the sialic acid groups that terminate the N-glycan chains of alpha-1 acid glycoprotein change in response to certain health conditions and may have a major impact on drug binding to alpha-1 acid glycoprotein. The interaction between native or desialylated alpha-1 acid glycoprotein and four representative drugs-clindamycin, diltiazem, lidocaine, and warfarin-was quantitatively evaluated using isothermal titration calorimetry. The calorimetry assay used here is a convenient and widely used approach to directly measure the amount of heat released or absorbed during the association processes of biomolecules in solution and to quantitatively estimate the thermodynamics of the interaction. The results showed that the binding of drugs with alpha-1 acid glycoprotein were enthalpy-driven exothermic interactions, and the binding affinity was in the range of 10-5-10-6 M. Desialylated alpha-1 acid glycoprotein showed significantly different binding with diltiazem, lidocaine, and warfarin compared with native alpha-1 acid glycoprotein, whereas clindamycin showed no significant difference. Therefore, a different degree of sialylation may result in different binding affinities, and the clinical significance of changes in sialylation or glycosylation of alpha-1 acid glycoprotein in general should not be neglected.

Common anti-haemostatic medications increase the severity of systemic infection by uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) causes urinary tract infections that can result in sepsis. The haemostatic system is protective in the pyelonephritis stage of ascending UPEC infection, but the role of the haemostatic system has not been investigated during sepsis. Here we utilize a zebrafish-UPEC systemic infection model to visualize infection-induced coagulation and examine the effects of commonly prescribed anti-haemostatic medications on the infection severity. Treatment of systemically infected zebrafish with warfarin, aspirin, or ticagrelor reduced host survival, while stabilization of clots with aminocaproic acid increased host survival. Anti-haemostatic drug treatment increased UPEC burden. Our findings provide evidence that commonly prescribed anti-haemostatic medications may worsen the outcome of severe UPEC infection.

Warfarin Induced Quenching of the Carbon Quantum Dots: Mechanism Study and Warfarin Sensor Construction

The mechanism of the fluorescence quenching of the CQDs by warfarin was determined and based on this study a simple, low cost and highly sensitive nanosensor was developed for determination of Warfarin in plasma samples. The carbon quantum dots with 3.5 µs lifetime (halflife of 2.4 µs) were synthesized by hydrothermal method and characterized. The fluorescence rate constant of 4.5 × 10⁴ s^-1 and quenching rate constant of 6.18 × 10⁴ s^-1 (from 10 μM warfarin that result in 17% lifetime reduction) was calculated. High quenching efficiency results in 21.63 L mmol^-1 Stern-Volmer constant and the study of pH and temperature also confirm the dynamic quenching mechanism. The second order rate constant of 6.18 × 10⁴ L mmol^-1 s^-1 was obtained for collisions between CQDs and warfarin. Based on this mechanism, a simple, low cost and very sensitive warfarin nanosensor was developed with calibration sensitivity of 21.63 L mmol^-1, working range of 0.10 - 12.00 μM and detection limit of 0.01 μM.

Retention and molecular-recognition mechanisms of molecularly imprinted polymers for warfarin derivatives and their application for the determination of warfarin in human serum

Monodisperse molecularly imprinted polymers (MIPs) for warfarin (WF), 4'-chlorowarfarin (CWF), 4'-bromowarfarin (BWF), 4'-nitrowarfarin (NWF) and 4'-methylwarfarin (MWF) (MIP_WF, MIP_CWF, MIP_BWF, MIP_NWF and MIP_MWF, respectively) were prepared using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate as a functional monomer and crosslinker, respectively, by multi-step swelling and polymerization. The retention and molecular-recognition properties of those MIPs were evaluated in HILIC, and reversed- and normal-phase modes. According to ¹H NMR studies, one-to-three complex formation of one WF or CWF molecule with three 4-VPY molecules occurred. Via computational approaches, the intermolecular interaction modes and energies between WF derivatives and 4-VPYs were evaluated by semi-empirical quantum chemistry methods and density functional theory calculations. Three major possible hydrogen bonding interaction modes were identified: the interactions between the 4-hydroxy group, α-proton (methylene C-H) and α-proton (methyl C-H) of the WF derivative and the nitrogen atoms of 4-VPYs. In HILIC and normal-phase modes, the interaction energies showed satisfactory correlations with the retention factors of the WF derivatives. In reversed-phase mode, the retention factors of the WF derivatives were described by the hydrophobicity and the acidity of the 4-hydroxy groups of the WF derivatives. These results demonstrate that three hydrogen bonding interactions in HILIC and normal-phase modes, and hydrogen bonding or ionic interactions and hydrophobic interactions in reversed-phase mode play important roles in the retention and molecular-recognition of the WF derivatives on MIPs. Furthermore, MIP_BWF was successfully applied to the determination of WF in human serum by column-switching LC with high accuracy, precision and selectivity and without template-leakage problems.

Nanofluid of magnetic-activated charcoal and hydrophobic deep eutectic solvent: Application in dispersive magnetic solid-phase extraction for the determination and preconcentration of warfarin in biological samples by high-performance liquid chromatography

In this study, for the first time, nanofluid of magnetic-activated charcoal and hydrophobic deep eutectic solvent (AC@Fe₃ O₄ -DES) based dispersive magnetic solid-phase extraction was successfully applied for the determination and preconcentration of warfarin in plasma and urine samples. The hydrophobic DES was prepared by mixing tetramethylammonium chloride (as hydrogen bond acceptor) and thymol (as hydrogen bond donor) and acted simultaneously as both carrier and stabilizer for magnetic nanoparticles. In this method, the nanofluid as a new extraction solvent was rapidly injected into the aqueous sample, which led to improvement of the mass transfer of the analytes into the sorbent and reduction of the extraction time. In the screening step, the fractional factorial design was applied for selecting some important parameters which significantly affected the extraction procedure. The effective parameters were then optimized by Box-Behnken design. Under the optimal conditions, the limits of detection were in the range of 0.3-1.6 ng/ml. A good linear range was observed in the range of 1.0-500.0 ng/ml for water and 5.0-500.0 ng/ml for urine and plasma. The intra- and inter-day relative standard deviations were 2.7-3.2 and 1.9-4.5% for five replications, respectively. Based on the results, the proposed method was successfully applied for the determination of warfarin in biological samples, using high-performance liquid chromatography.

Dried Blood Spot Self-Sampling with Automated Capillary Electrophoresis Processing for Clinical Analysis

A simple and convenient concept of blood sampling followed by a fully automated analysis is presented. A disposable sampling kit is used for accurate self-sampling of capillary blood from a finger prick. A high-throughput blood sampling is thus enabled, which is essential in many clinical assays and considerably improves life quality and comfort of involved subjects. The collected blood samples are mailed to a laboratory for a fully automated dried blood spot (DBS) processing and analysis, which are performed with a commercial capillary electrophoresis instrument. Quantitative results are obtained within 20 min from the DBS delivery to the laboratory. The presented concept is exemplified by the determination of warfarin blood concentrations and demonstrates excellent analytical performance. Moreover, this concept is generally applicable to a wide range of endogenous and exogenous blood compounds and represents a novel and attractive analytical tool for personalized health monitoring.

A Study of Proton Pump Inhibitors and Other Risk Factors in Warfarin-Associated Gastrointestinal Bleeding

Background

Warfarin users are at increased risk for gastrointestinal bleeding (GIB). History of GIB, stroke, cardiovascular or chronic kidney disease, age greater than 65 years, and drug interaction with proton pump inhibitors (PPI) have previously been identified as risk factors for GIB in warfarin users. We hypothesized that concomitant use of warfarin and PPI would increase the incidence of GIB relative to warfarin use alone.

Methods

We did a retrospective review of medical records of 626 patients taking warfarin for at least two weeks. Parameters including age, concomitant medication use (non-steroidal anti-inflammatory drugs (NSAID), aspirin, selective serotonin reuptake inhibitors (SSRIs), PPI, and anti-platelet drug), history of GIB, chronic renal failure (CRF), and peptic ulcer disease (PUD) prior to warfarin use were analyzed.

Results

Variables that increase the likelihood of bleeding in warfarin users included aspirin, PPI, history of PUD, history of previous GIB, CRF, and elevated prothrombin time (PT)/international normalized ratio (INR) values. Concomitant antiplatelet use showed a slight increase in GIB but this was not statistically significant (p=0.082). NSAID use and SSRI use were not associated with a higher risk of GIB among warfarin users. Patients who are on PPI and warfarin simultaneously are more likely to be on acetylsalicylic acid (ASA) or have a history of PUD, GIB, or CRF, all of which are associated with increased incidences of GIB.

Conclusions

Although concomitant use of warfarin and PPI appears to be associated with an increased incidence of GIB, these patients are more likely to have other risk factors that also increase the risk of a GIB outcome. Therefore, the interaction between PPI and warfarin is clinically insignificant.

Carbon based nanomaterials for the detection of narrow therapeutic index pharmaceuticals

Precise detection of important pharmaceuticals with narrow therapeutic index (NTI) is very critical as there is a small window between their effective dose and the doses at which the adverse reactions are very likely to appear. Regarding the fact that various pharmacokinetics will be plausible while considering pharmacogenetic factors and also differences between generic and brand name drugs, accurate detection of NTI will be more important. Current routine analytical techniques suffer from many drawbacks while using novel biosensors can bring up many advantages including fast detection, accuracy, low cost with simple and repeatable measurements. Recently the well-known carbon Nano-allotropes including carbon nanotubes and graphenes have been widely used for development of different Nano-biosensors for a diverse list of analytes because of their great physiochemical features such as high tensile strength, ultra-light weight, unique electronic construction, high thermo-chemical stability, and an appropriate capacity for electron transfer. Because of these exceptional properties, scientists have developed an immense interest in these nanomaterials. In this case, there are important reports to show the effective Nano-carbon based biosensors in the detection of NTI drugs and the present review will critically summarize the available data in this field.

Hydrophobic borneol-based natural deep eutectic solvents as a green extraction media for air-assisted liquid-liquid micro-extraction of warfarin in biological samples

In the present study, a new generation of water-immiscible natural deep eutectic solvents (DESs) was synthesized using borneol as a hydrogen-bonding acceptor and decanoic acid, oleic acid, and thymol as a hydrogen-bonding donor in different molar ratios. These green hydrophobic solvents which are chemically stable in aqueous solutions were used as extraction solvents for isolation and pre-concentration of warfarin in biological samples. In this method, fine droplets of DESs were dispersed into the sample solution by using the air-assisted liquid-liquid micro-extraction method to accelerate the cloudy emulsion system formation and increase the mass transfer of the analyte to the DES-rich phase. The borneol based deep eutectic solvent is a worthy generation of the extraction solvents in the ALLME method due to low-cost and less toxicity. A Plackett-Burman design was utilized for screening the experimental parameters. The effective parameters were then optimized by Box-Behnken design (BBD). Optimized extraction conditions were pH of sample solution of 3.9, number of aspiration/dispersion cycles of 15, the volume of DES of 60 μL, and rate and time of centrifuge of 6000 rpm and 10 min, respectively. Under the optimized conditions, the developed NADES-ALLME method exhibited a wide linear range of 5-500 µg L ^- 1 for plasma and urine samples with satisfactory recoveries above 88.80%. Limit of detections (LODs) and Limit of quantifications (LOQs) of warfarin were in the ranges of 0.5-2.7 and 1.65-8.91, respectively. The enrichment factors were obtained in the range of 148-164 and precisions were lower than 5.87%. Finally, the proposed method was successfully employed for the analysis of warfarin in human urine and plasma samples.

Progress in Pretreatment and Analytical Methods of Coumarins: An Update since 2012 - A Review

Coumarins are widely used due to their wide range of biological activities, but the long-term or excessive use of coumarin flavors can pose serious health hazards. Therefore, sensitive and specific methods for the quantification of these compounds in different matrices have been developed. In this review, an updated overview of the latest trends in sample preparation techniques and methods used to detect coumarins from March 2012 to April 2019 is provided. This study reviews different analytical methods (such as liquid chromatography coupled with different detectors, electrochemical sensors, capillary electrophoresis, etc.) and different pretreatment methods (such as liquid-liquid extraction, solid-phase extraction, dispersive liquid-liquid microextraction, etc.). Different methods for the pretreatment and determination of coumarins in plant, food, environmental, pharmaceutical and biological samples are summarized, discussed and compared.HighlightsProgress in pretreatment and analytical methods of coumarins are summarized.Fundamentals, instrumentation and applications of purification and quantification are summarized and compared.Optimization of experimental conditions are discussed.Newly emerged eco-friendly methods are introduced.

Detection and quantification of warfarin in pharmaceutical dosage form and in spiked human plasma using surface enhanced Raman scattering

Analytical approaches for the quantitation of warfarin in plasma are high in demand. In this study, a novel surface enhanced Raman scattering (SERS) technique for the quantification of the widely used anticoagulant warfarin sodium in pharmaceutical dosage form and in spiked human plasma was developed. The colloidal-based SERS measurements were carefully optimized considering the laser wavelength, the type of metal nanoparticles, their surface functionalization and concentration as well as the time required for warfarin to associate with the metal surface. Poly(diallyldimethylammonium chloride) coated silver nanoparticles (PDDA-AgNPs) were established as a substrate which greatly enhanced the weak warfarin Raman signal with high reproducibility. The limit of detection was calculated in both water and human plasma to be 0.56 nM (0.17 ngmL^-1) and 0.25 nM (0.08 ngmL^-1) respectively, with a high degree of accuracy and reproducibility. The proposed method is simple, economical, and easily applied for routine application requiring only small plasma samples and also could be potentially useful for pharmacokinetic research on warfarin.

Prioritizing rs7294 as a mirSNP contributing to warfarin dosing variability

Aim: The role of mirSNPs in the 3'UTR of VKORC1, CYP2C9 and CYP4F2 genes that could influence warfarin dose variability via a discrete miRNA-mediated mechanism remains unexplained. Methods: Genotypic data in the 1000 Genomes dataset were analyzed for pair-wise linkage disequilibrium and allelic enrichment. Results: MirSNP rs7294 in the 3'UTR of VKORC1 gene displayed varying strengths of linkage disequilibrium with rs9923231 and rs9934438 across populations, albeit consistently associated with higher warfarin dose requirements based on genome-wide association studies, meta-analysis and population-based association studies. In silico analysis predicted altered hybrid stability for the hsa-miR-133a-3p conserved binding site, providing evidence for miRNA-mediated gene regulation. Conclusion: The results support the inclusion of rs7294 as a functional variable for population-specific dosing algorithms to improve dosing accuracy.

Nanoplasmonic biosensor device for the monitoring of acenocoumarol therapeutic drug in plasma

Acenocoumarol (Sintrom®) is an oral anticoagulant prescribed for the treatment of a variety of thromboembolic disorders such as atrial fibrillation and thrombosis or embolism. It inhibits fibrin production preventing clot formation. Acenocoumarol has a narrow therapeutic range, and its effects depend on several factors, such as body weight, age, metabolism, diet, certain medical conditions or the intake of additional drugs, among others. A higher dose may result in the risk of bleeding, while if it is too low, the risk of blood clot can increase. Complementary tools that allow the therapeutic drug monitoring (TDM) of acenocoumarol plasmatic levels from the starting of the treatment would be of paramount importance to personalize the treatment. Point-of-care (POC) devices can offer an added value in facilitating on-site monitoring (i.e. hospitals, primary care doctor or even by the patient itself) and can aid in dosage management. With this aim, we have developed a compact and simple nanoplasmonic sensing device based on gold nanodisks for the rapid monitoring of acenocoumarol, using highly specific polyclonal antibodies produced against this drug. A specific and reproducible label free indirect competitive assay has been developed and the viability of performing the evaluation directly in plasma diluted 1:1 has been demonstrated. A limit of detection (LOD) of only 0.77 ± 0.69 nM, an IC₅₀ of 48.2 ± 5.12 nM and a dynamic range between 3.38 ± 1.33 nM and 1154 ± 437 nM were achieved, which easily fit within the drug plasma levels of acenocoumarol, making this approach a highly attractive option for its decentralized monitoring in human plasma.

A highly selective and sensitive Tb3+-acetylacetone photo probe for the assessment of acetazolamide in pharmaceutical and serum samples

A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of Acetazolamide in pharmaceutical tablets and serum samples using photo probe Tb³⁺-ACAC. The Acetazolamide can remarkably quench the luminescence intensity of Tb³⁺-ACAC complex in DMSO at pH 6.8 and λ_ex = 350 nm. The quenching of luminescence intensity of Tb³⁺-ACAC complex especially the electrical band at λ_em = 545 nm is used for the assessment of Acetazolamide in the pharmaceutical tablet and serum samples. The dynamic range found for the determination of Acetazolamide concentration is 4.49 × 10^-9-1.28 × 10^-7 mol L^-1, and the limit of detection (LOD) and limit of quantification (LOQ) are (4.0 × 10^-9 and 1.21 × 10^-8) mol L^-1, respectively.

A novel approach to assess the spontaneous gastrointestinal bleeding risk of antithrombotic agents using Apc min/+ mice

Assessment of the bleeding risk of antithrombotic agents is usually performed in healthy animals with some form of vascular injury to peripheral organs to induce bleeding. However, bleeding observed in patients with currently marketed antithrombotic drugs is typically spontaneous in nature such as intracranial haemorrhage (ICH) and gastrointestinal (GI) bleeding, which happens most frequently on top of preexisting pathologies such as GI ulcerations and polyps. Apc min/+ mice are reported to develop multiple adenomas through the entire intestinal tract and display progressive anaemia. In this study, we evaluated the potential utility of Apc min/+ mice as a model for assessing spontaneous GI bleeding with antithrombotic agents. Apc min/+ mice exhibited progressive blood loss starting at the age of nine weeks. Despite the increase in bleeding, Apc min/+ mice were in a hypercoagulable state and displayed an age-dependent increase in thrombin generation and circulating fibrinogen as well as a significant decrease in clotting times. We evaluated the effect of warfarin, dabigatran etexilate, apixaban and clopidogrel in this model by administering them in diet or in the drinking water to mice for 1–4 weeks. All of these marketed drugs significantly increased GI bleeding in Apc min/+ mice, but not in wild-type mice. Although different exposure profiles of these antithrombotic agents make it challenging to compare the bleeding risk of compounds, our results indicate that the Apc min/+ mouse may be a sensitive preclinical model for assessing the spontaneous GI bleeding risk of novel antithrombotic agents.

Enzyme-catalyzed Michael addition for the synthesis of warfarin and its determination via fluorescence quenching of l-tryptophan

A sensitive fluorescence sensor for warfarin was proposed via quenching the fluorescence of l-tryptophan due to the interaction between warfarin and l-tryptophan. Warfarin, as one of the most effective anticoagulants, was designed and synthesized via lipase from porcine pancreas (PPL) as a biocatalyst to catalyze the Michael addition of 4-hydroxycoumarin to α, β-unsaturated enones in organic medium in the presence of water. Furthermore, the spectrofluorometry was used to detect the concentration of warfarin with a linear range and detection limit (3σ/k) of 0.04-12.0μmolL^-1 (R²=0.994) and 0.01μmolL^-1, respectively. Herein, this was the first application of bio-catalytic synthesis and fluorescence for the determination of warfarin. The proposed method was applied to determine warfarin of the drug in tablets with satisfactory results.

Interaction of quercetin and its metabolites with warfarin: Displacement of warfarin from serum albumin and inhibition of CYP2C9 enzyme

Flavonoids are ubiquitous molecules in nature with manifold pharmacological effects. Flavonoids interact with several proteins, and thus potentially interfere with the pharmacokinetics of various drugs. Though much is known about the protein binding characteristics of flavonoid aglycones, the behaviour of their metabolites, which are extensively formed in the human body has received little attention. In this study, the interactions of the flavonoid aglycone quercetin and its main metabolites with the albumin binding of the oral anticoagulant warfarin were investigated by fluorescence spectroscopy and ultrafiltration. Furthermore, the inhibitory effects of these flavonoids on CYP2C9 enzyme were tested because the metabolic elimination of warfarin is catalysed principally by this enzyme. Herein, we demonstrate that each tested flavonoid metabolite can bind to human serum albumin (HSA) with high affinity, some with similar or even higher affinity than quercetin itself. Quercetin metabolites are able to strongly displace warfarin from HSA suggesting that high quercetin doses can strongly interfere with warfarin therapy. On the other hand, tested flavonoids showed no or weaker inhibition of CYP2C9 compared to warfarin, making it very unlikely that quercetin or its metabolites can significantly inhibit the CYP2C9-mediated inactivation of warfarin.

Estimation of plasma levels of warfarin and 7-hydroxy warfarin by high performance liquid chromatography in patients receiving warfarin therapy

Warfarin is one of the most commonly prescribed oral anticoagulant for prevention of thromboembolic events. The effect of this drug is measured by monitoring prothrombin time expressed as International Normalized Ratio (INR). In some cases, however, the measurement of plasma concentration of warfarin was emphasized. In the present study, reversed phase high performance liquid chromatography (HPLC) was used to estimate the plasma drug levels. A total of 185 patients were enrolled in this study. Five milliliter of venous blood was collected using sodium EDTA tubes for pharmacokinetic analysis. Solid phase extraction was used to recover the warfarin and it's metabolite from plasma using isopropanol and potassium phosphate buffer (40:60) mobile phase. Warfarin, 7-hydroxy warfarin and carbamazepine (internal standard) were separated on a C18 column and had the retention time 3.6 min, 2.9 min and 5.9 min, respectively. The assay was linear in warfarin concentration ranges of 0.1-5 μg/ml. The extraction recovery was found to be ≃85%. The mean plasma concentrations of warfarin and 7-hydroxy warfarin were found to be 3.47 ± 1.87 (SD) μg/ml, 1.25 ± 0.81 (SD) μg/ml, respectively. Through the present study the plasma concentrations of warfarin, 7-hydroxy warfarin and their metabolic ratio was determined. The assay was sensitive to follow warfarin pharmacokinetics in a patient with warfarin therapy for 3 months and above.

Exogenous albumin inhibits sorafenib-induced cytotoxicity in human cancer cell lines

Sorafenib is an orally administered multikinase inhibitor that exhibits anti-angiogenic and anti-tumor activity. Sorafenib is also known to bind to protein (>99.5%), suggesting protein binding may be involved in sorafenib pharmacokinetic variability. Albumin is a major drug-binding protein. In this study, we examined the effect of albumin on sorafenib-induced cytotoxicity using two in vitro culture cell lines, human hepatoma Huh-7 cells and androgen-independent prostate cancer PC-3 cells. The cells were cultured and incubated, and cytotoxicity was assessed. Results were confirmed by western blotting. The presence of exogenous albumin markedly blocked the sorafenib-induced cytotoxicity in the two cell lines. Albumin concentration, the change of pharmacological signal transduction as Raf-B, vascular endothelial growth factor (VEGF), and phosphorylation of MEK1/2 or ERK1/2 were found to be decreased by sorafenib. Co-incubation of warfarin, a representative coumarin anticoagulant and potent binding activity, with albumin enhanced the cytotoxic effects by sorafenib. These mechanisms depend on the high binding proper ties of sorafenib and exogenous albumin. Furthermore, we investigated the effects of endo genous albumin expression on sorafenib-induced cytotoxicity using the siRNA knockdown system or transfected expression vector assay. However, the cytotoxic effects by sorafenib showed little change either with the knockdown or overexpression of albumin. Our results suggest that particular care should be taken with albuminemia or the combined use of drugs with a high affinity for albumin, such as warfarin, and sorafenib in the treatment of cancer patients. Our findings may be useful to the cancer therapeutic strategy by sorafenib.

Developmental effects of coumarin and the anticoagulant coumarin derivative warfarin on zebrafish (Danio rerio) embryos

Coumarin and warfarin, two substances which are intensively metabolized in animals and humans, were tested for teratogenicity and embryo lethality in a 3-day in vitro assay using zebrafish embryos. Warfarin is a coumarin derivative, but in contrast to the mother substance warfarin has anticoagulant properties. Both substances produced teratogenic and lethal effects in zebrafish embryos. The LC(50) and EC(50) values for coumarin are 855 μM and 314 μM, respectively; the corresponding values for warfarin are 988 μM and 194 μM. For coumarin, three main or fingerprint endpoints (malformation of head, tail and growth retardation) were identified, whereas malformation of tail was the only fingerprint endpoint of warfarin. The analysis of the ratios between the zebrafish embryo effect concentrations of both substances and human therapeutic plasma concentrations confirmed the teratogenic potential of warfarin, as well as the equivocal status of coumarin.

Determination of plasma warfarin concentrations in Korean patients and its potential for clinical application

BACKGROUND

Warfarin is a widely used oral anticoagulant with broad within- and between-individual dose requirements. Warfarin concentrations can be monitored by assessing its pharmacologic effects on International Normalized Ratio (INR). However, this approach has not been applied in the routine clinical management of patients receiving warfarin therapy. We performed a plasma warfarin assay using high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) to determine if such an assay can be utilized in routine clinical practice.

METHODS

We included a total of 105 patients with atrial fibrillation, and who were receiving warfarin for more than 1 yr. The plasma concentrations of total warfarin and 7-hydroxywarfarin were determined by HPLC-MS/MS (Waters, UK). We assessed the association between warfarin dose, concentration, and INR as well as the effects of these factors on warfarin concentrations.

RESULTS

The mean maintenance dose of warfarin in 105 patients was 4.1 +/-1.3 mg/day (range, 1.7-8.0 mg/day) and their mean plasma warfarin concentration was 1.3+/-0.5 mg/L. We defined a concentration range of 0.6-2.6 mg/L (corresponding to the 2.5th to 97.5th percentile range of the Plasma warfarin levels in the 74 patients showing INR within target range) as the therapeutic range for warfarin. The correlation of warfarin dose with warfarin concentration (r(2)=0.259, P<0.001) was higher than that with INR (r(2)=0.029, P=0.072).

CONCLUSIONS

There was a significant correlation between warfarin dose and plasma warfarin concentrations in Korean patients with atrial fibrillation. Hence, plasma warfarin monitoring can help determine dose adjustments and improve our understanding of individual patient response to warfarin treatment.

Adverse interaction of warfarin and paracetamol: evidence from a post-mortem study

PURPOSE

The aim of the study was to establish the prevalence and nature of potential adverse drug combinations of warfarin in a large post-mortem toxicology database. The concomitant use of warfarin and non-steroidal anti-inflammatory drugs (NSAIDs) was of interest as these drugs have been associated with internal bleeding both in clinical and post-mortem study settings. Another purpose was to obtain facts related to the questioned safety of warfarin-paracetamol and warfarin-tramadol combinations.

METHODS

The post-mortem database was searched for a 1-year period. All warfarin-positive cases and cases containing interacting drugs, as defined by the SFINX interaction database (Swedish, Finnish, Interaction X-referencing), were included. For controls, all cases containing paracetamol or tramadol were also included, and for each warfarin-positive case, an age-, sex- and alcohol-matched control case was sourced. The contribution of anticoagulant use to the deaths was evaluated from the death certificates based on medico-legal autopsies.

RESULTS

In 33% of the 328 warfarin-positive cases, at least one interacting drug was present, and paracetamol was the most abundant, accounting for 49% (n = 53). When paracetamol and warfarin were detected simultaneously, the number of fatal bleeds was 4.6 and 2.7 times higher compared to paracetamol or warfarin use alone respectively. The presence of an NSAID in combination with warfarin was rare, as only six cases were identified. A majority (66%) of the post-mortem blood samples had a warfarin concentration below 0.5 mg/l, and for the rest of the cases, the mean concentration was 0.70 mg/l.

CONCLUSIONS

This study supports the clinical evidence suggesting that warfarin-paracetamol interactions may create significant life-threatening conditions. It also accentuates the significant role post-mortem database research can have in improving drug safety.