Development of an UHPLC-UV-Method for Quantification of Direct Oral Anticoagulants: Apixaban, Rivaroxaban, Dabigatran, and its Prodrug Dabigatran Etexilate in Human Serum

[Drug-drug interactions-How can we protect ourselves from the flood of information?]

Physicians look at drug-drug interactions (DDI), or more correctly xenobiotic interactions, in an emotional mixture of fear and interest, due to the apparently countless number of adverse drug effects (ADE) that can occur. The interactions as such are seen as errors; however, interactions cannot be avoided and are an inevitable part of the normal work of physicians. The problem is how to recognize interactions and how to handle them. A xenobiotic interaction can often even improve the effectiveness of a pharmacotherapy and minimize the risks. If all examples of what can possibly happen are not necessarily counted, the flood of information becomes relatively manageable. There are only seven different classes of interactions, four pharmacodynamic and three pharmacokinetic interactions. Currently, there are hotlines and both analogue as well as digital databanks to answer questions and address uncertainties, unfortunately of markedly different quality! Aids, such as therapeutic drug monitoring (TDM) supplement these offers. Every pharmacokinetic interaction can be recognized by determination of the concentration of the active agent. The comprehensive clinical pharmacological TDM report explain the information contained in the concentration of the active agent about the individual patient from whom the blood was drawn. All physicians can learn how to compile the clinical pharmacological TDM report by themselves or they can request it in interdisciplinary cooperation via a council. Medical expertise in handling xenobiotic interactions not only opens the door to adaptation of the pharmacotherapy to the needs of the individual patient but also saves huge budget resources for the healthcare system.

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of free and total dabigatran in human plasma and its application to a pharmacokinetic study

A high performance liquid chromatography tandem mass spectrometric method for the determination of free and total dabigatran in human plasma has been developed and validated using stable labeled internal standard (IS) as dabigatran D₄. The extraction of analyte and IS was accomplished by solid phase extraction technique. Chromatographic separations were achieved using Peerless basic C8 (150 x 4.6) mm, 5µ column eluted at flow rate of 1 mL/min with mobile phase Acetonitrile: 5 mM ammonium formate: Methanol and 0.2% formic acid (30:20:50, v/v/v). The run time of method was about 2.5 min with elution times of dabigatran and dabigatran D₄ at around 1.2 min. The multiple reaction monitoring transitions (Q₁/Q₃) were set at 472/289, 172 (m/z) for dabigatran and 476/293 (m/z) for dabigatran D₄. The calibration curves were linear (r² ≥0.99) over the range of 1.04 - 406.49 ng/mL.The presented method was successfully employed in analysis of pharmacokinetic studies with an added advantage of demonstrating the effect of co-administration of dabigatran with the proton pump inhibitor pantoprazole on bioavailability and pharmacokinetic characteristics. Re-analysis of incurred sample resulted with >98% compliance indicating good assay precision of target analytes.Re-analysis of incurred sample resulted with >98% compliance which indicated good assay precision of target analytes.

Stability-indicating RP-HPLC assay of three novel oral anticoagulants binary mixtures with rosuvastatin calcium: Application to pharmaceutical preparations and human plasma

The binary mixtures of the novel oral anticoagulants (NOACs); Apixaban (APX), Edoxaban tosylate (EDX) and Rivaroxaban (RIV) with the lipid lowering statin; Rosuvastatin calcium were analyzed using a validated HPLC-DAD method. This method was suitable for the quantitative assay of the targeted mixtures in tablets and human plasma. The analysis in dosage form was a stability indicating one where the drugs were separated from possible degradation products arising from applying different stress conditions. For analysis in human plasma, EDX was used as internal standard in APX/ROS and RIV/ROS mixtures, while APX was used as internal standard in EDX/ROS mixture and the method was validated according to FDA regulation for analysis in biological fluids. A ZORBAX Eclipse column C18 (4.6 × 150 mm × 5 µm) was used as stationary phase with a gradient eluting mobile phase composed of acidified water and acetonitrile. The method selectivity was demonstrated by its ability to simultaneously analyze the drugs in presence of possible forced degradation products and dosage form excipients and in presence of plasma interferences (analysis in biological fluid) at a single wavelength (291 nm) with the use of the internal standard. The simplicity of the method emphasizes its capability to analyze the drugs in pharmaceutical preparations and human plasma. This is very important in regular clinical monitoring of the drugs plasma concentrations for cardiovascular patients medicated with either of these combinations, as prophylaxis from stroke, in order to prevent severe bleeding and to achieve optimum dose adjustment.

A liquid chromatography-tandem mass spectrometry method for the determination of apixaban in human plasma and its application to pharmacokinetics studies in the Indian population

Apixaban is a novel oral anticoagulant intended to treat and prevent blood clots and to prevent strokes in patients with nonvalvular atrial fibrillation. The development and validation of a fast, selective, accurate, and precise method using high-performance liquid chromatography tandem mass spectrometry is described for the estimation of apixaban in human plasma, with apixaban ¹³CD₃ as an internal standard (IS). Using a reverse phase Gemini C18 column (50 mm × 4.6 mm, 3 μm) and a mixture of acetonitrile (2 mM) and ammonium formate buffer (50 : 50 v/v) as the mobile phase, chromatographic separation was achieved following extraction via a solid-phase extraction process. To track multiple reaction monitoring transitions set at 460/443 (m/z) and 464/447 (m/z) for apixaban and apixaban ¹³CD₃, respectively, liquid chromatography coupled with triple quadrupole mass spectrometry was employed. A concentration linearity range between 1.01 and 280.00 ng mL^-1 was validated with regression ≥0.99, and the method was successfully applied to apixaban pharmacokinetics analysis. At a flow rate of 1.0 mL min^-1, the run time was around 1.8 min, which is short. With an extraction recovery of >73% for both apixaban and apixaban ¹³CD₃, the method was sensitive, with a limit of quantitation of 1.01 ng mL^-1. The inter-day/between-run precision ranged from 1.21% to 3.21%, while the accuracy ranged from 96.5% to 102%. For pharmacokinetics analysis, the validated method was applied. The percentage difference between findings from samples that were reanalyzed and samples that were initially analyzed was within ±20%. With high-quality assay specificity and accuracy in relation to apixaban analysis in human plasma under the experimental conditions used, the method provided is accurate.

Development and validation of LC-MS/MS method for simultaneous determination of dabigatran etexilate and its active metabolites in human plasma, and its application in a pharmacokinetic study

Dabigatran is a direct thrombin inhibitor widely used for preventing various thrombotic events. Although there are several established LC-MS/MS based methods for quantification of plasma dabigatran etexilate and its active metabolites (dabigatran and dabigatran acylglucuronide), so far, there are no studies for simultaneous quantification of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in human plasma samples. In the present study, a novel and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for assessment of dabigatran pharmacokinetics in human plasma samples according to FDA guidelines. We used the new method to simultaneously quantify dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in human plasma samples. After deproteinization using acetonitrile, the supernatants were evaporated, dissolved in a mobile phase, and finally injected onto an HPLC system with a silica-based C₁₈ reverse-phase column. Mass spectrometer system was operated in multiple reaction monitoring mode (MRM) (dabigatran etexilate: m/z 629.464→290.100; dabigatran: m/z 472.300→289.100, and dabigatran acylglucuronide: m/z 648.382→289.100) and all the components were confirmed using positive electrospray ionization (ESI). Correlation coefficients > 0.999 were achieved for all the calibration curves with linear regression. The intra-day and inter-day accuracies of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide were 95.84-109.44 %, 99.4-103.42 %, and 98.37-104.42 %, respectively, while their corresponding precisions were 3.84-9.79, 1.07-8.76 %, and 2.56-4.51 %, respectively. We successfully applied the new method to determine the pharmacokinetic profiles of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in humans. Our findings demonstrated the method as robust, reliable, and sensitive.

ROTEM Testing for Direct Oral Anticoagulants

Direct oral anticoagulants (DOACs) are increasingly used worldwide for the prevention of stroke in patients with atrial fibrillation and to prevent or treat venous thromboembolism. In situations such as serious bleeding, the need for urgent surgery/intervention or the management of a thromboembolic event, the laboratory measurement of DOACs levels or anticoagulant activity may be required. Rotational thromboelastometry (ROTEM) is a viscoelastic hemostatic assay (VHA) which has been used in emergencies (trauma and obstetrics), and surgical procedures (cardiac surgery and liver transplants), but experience with this assay in DOACs-treated patients is still limited. This article reviews the use of ROTEM in the setting of DOACs therapy, focusing on DOACs-associated bleeding and the use of this VHA for the management of reversal strategies for DOACs-associated anticoagulation.

Impact of a commercially available DOAC absorbent on two integrated procedures for lupus anticoagulant detection

BACKGROUND

Lupus anticoagulant (LA)-detection in anticoagulated patients is an unmet need, which becomes even more cogent with the introduction of direct oral anticoagulants (DOAC) that may lead to false-positive results.

AIMS

We aimed to investigate the effect of a commercially available DOAC absorbent on residual drug concentrations, and on integrated procedures for LA-detection.

METHODS

Blood from patients treated for atrial fibrillation with either dabigatran (n = 39), rivaroxaban (n = 55), apixaban (n = 47) or edoxaban (n = 47) were collected at peak and trough, and centralized for testing with two LA integrated procedures [i.e., the silica clotting time (SCT) and dilute Russel viper venom (dRVVT)] before and after DOAC absorbent exposure.

RESULTS

The commercially available DOAC absorbent investigated in this study proved effective in reducing the concentrations of all the investigated DOAC, although small residual drug was detected after absorption, especially in patients on edoxaban. Results mimicking LA were observed in patients on DOAC before absorbent exposure, especially for rivaroxaban when testing was performed with dRVVT (88% rate at peak and 20% at trough) and much less with SCT (12% at peak and 8% at trough). The correspondent rate of results mimicking LA in patients on rivaroxaban after exposure was reduced [dRVVT (peak 8%, trough 4%); SCT (peak and trough 8%)], but not abolished.

CONCLUSIONS

Overall, in vitro DOAC absorbance by active charcoal compounds is a useful laboratory tool for LA-detection in patients on DOAC. Caution should however be exerted when used in daily practice.

Binding of direct oral anticoagulants to the FA1 site of human serum albumin

The anticoagulant therapy is widely used to prevent and treat thromboembolic events. Until the last decade, vitamin K antagonists were the only available oral anticoagulants; recently, direct oral anticoagulants (DOACs) have been developed. Since 55% to 95% of DOACs are bound to plasma proteins, the in silico docking and ligand-binding properties of drugs apixaban, betrixaban, dabigatran, edoxaban, and rivaroxaban and of the prodrug dabigatran etexilate to human serum albumin (HSA), the most abundant plasma protein, have been investigated. DOACs bind to the fatty acid (FA) site 1 (FA1) of ligand-free HSA, whereas they bind to the FA8 and FA9 sites of heme-Fe(III)- and myristic acid-bound HSA. DOACs binding to the FA1 site of ligand-free HSA has been validated by competitive inhibition of heme-Fe(III) recognition. Values of the dissociation equilibrium constant for DOACs binding to the FA1 site (ie, ^calc K_DOAC ) derived from in silico docking simulations (ranging between 1.2 × 10^-8 M and 1.4 × 10^-6 M) agree with those determined experimentally from competitive inhibition of heme-Fe(III) binding (ie, ^exp K_DOAC ; ranging between 2.5 × 10^-7 M and 2.2 × 10^-6 M). In addition, this study highlights the inequivalence of rivaroxaban binding to mammalian serum albumin. Given the HSA concentration in vivo (~7.5 × 10^-4 M), values of K_DOAC here determined indicate that the formation of the HSA:DOACs complexes in the absence and presence of FAs and heme-Fe(III) may occur in vivo. Therefore, HSA appears to be an important determinant for DOACs transport.

Liquid chromatography-tandem mass spectrometry method for determination of rivaroxaban in human plasma and its application to a pharmacokinetic study

A high-performance liquid chromatography tandem mass spectrometric method for the determination of Rivaroxaban in human plasma has been developed and validated using Rivaroxaban D₄ as an internal standard. The extraction of analyte and internal standard was accomplished by solid phase extraction technique. The method has been validated over a concentration range of 5.96-801 ng/mL. Chromatographic separations were achieved using Gemini C18, 150 mm × 4.6 mm, 5 µm, column eluted at flow rate of 1.5 mL/min with mobile phase (acetonitrile: ammonium acetate buffer (80:20 v/v)). The overall run time of method was about 1.8 min with elution times of Rivaroxaban and its internal standard Rivaroxaban D₄ at around 1.18 min. The multiple reaction monitoring transitions were set at 436/145 (m/z) and 440/145 (m/z) for Rivaroxaban and Rivaroxaban D₄, respectively. The calibration curves were linear (r²≥ 0.99) over the range of 5.96-801 ng/mL with lower limit of quantitation validated at 5.96 ng/mL. Extraction recoveries were >88% for both rivaroxaban and its stable labeled internal standard rivaroxaban D₄. The inter-day/between run precisions were ranged from 1.08% to 3.75%, while accuracy ranged from 96.3% to 102%. The presented method was used in pharmacokinetic study in healthy volunteers. Results of incurred sample reanalysis were within the acceptance range of ±20% of original value, for 98.3% of samples reanalyzed. This indicated good assay precision of target analytes in their real matrix at the employed experimental conditions. The applicability of the assay for the determination of the pharmacokinetic parameters was demonstrated.

DOAC plasma levels measured by chromogenic anti-Xa assays and HPLC-UV in apixaban- and rivaroxaban-treated patients from the START-Register

INTRODUCTION

To measure direct factor Xa inhibitor (apixaban, edoxaban, rivaroxaban) concentrations, dedicated chromogenic anti-Xa assays are recommended as suitable methods to provide rapid drug quantification. Moreover, the high-performance liquid chromatography with ultraviolet detection (HPLC-UV) is reported as a reliable quantitative technique. We investigated seven anti-Xa assays and an HPLC-UV method for measurement of apixaban and rivaroxaban levels in patients enrolled in the START-Register.

METHODS

A total of 127 apixaban and 124 rivaroxaban samples were tested by HPLC-UV and the following anti-Xa assays: Biophen DiXaI and Heparin LRT (Hyphen BioMed), Berichrom and Innovance Heparin (Siemens), STA-Liquid Anti-Xa (Stago Diagnostics), Technochrom anti-Xa (Technoclone), and HemosIL Liquid Anti-Xa (Werfen). Each method was performed in one of the participating laboratories: Bologna, Cremona, Florence, and Padua.

RESULTS

Our data confirmed the overestimation of apixaban and rivaroxaban levels by the antithrombin-supplemented anti-Xa method (Berichrom). Performances and reproducibility of the six anti-Xa assays not supplemented with antithrombin and the HPLC-UV method were good, with limits of quantification from 8-39 ng/mL (apixaban) and 15-33 ng/mL (rivaroxaban). The six chromogenic methods showed good concordances with the quantitative HPLC-UV [bias: -26.9-22.3 ng/mL (apixaban), -11.3-18.7 ng/mL (rivaroxaban)]. Higher bias and wider range between limits of agreement were observed at higher concentrations [<100 ng/mL: bias -21.3-4.1 ng/mL (apixaban) and -6.2-3.8 ng/mL (rivaroxaban); >200 ng/mL: bias -42.2-36.8 ng/mL (apixaban) and -20.1-68.9 ng/mL (rivaroxaban)].

CONCLUSION

Overall, the anti-Xa assays not supplemented with antithrombin and the HPLC-UV method proved to be suitable for apixaban and rivaroxaban quantification.

Development, validation and application of a new HPLC-DAD method for simultaneous quantification of apixaban, dabigatran, edoxaban and rivaroxaban in human plasma

Direct oral anticoagulants (DOACs) have been commonly used for the treatment of venous thromboembolism and for the prevention of stroke in patients with atrial fibrillation. Despite not being initially recommended, monitoring DOACs plasma concentrations is now recognized as essential in emergency situations and in special populations. Moreover, the inter-individual variability found in real studies as well as the high reported non-adherence are corroborating the importance of determining the individual relationship between administered doses, plasma concentrations and pharmacological effects. Therefore, accurate but user-friendly bioanalytical techniques are required to monitor DOACs plasma concentrations in routine clinical practice and phase IV clinical trials. Herein, a fast and simple high performance liquid chromatography (HPLC) method coupled to diode array detection (DAD) was developed, validated and applied to quantify the four currently marketed DOACs (apixaban, edoxaban, dabigatran and rivaroxaban). Sample preparation was performed by solid phase extraction followed by evaporation and concentration of the analytes. Chromatographic separation was accomplished within 6 min on a reversed-phase column (octadecyl-silica packing material; 55 mm × 4 mm, 3 μm particle size), applying a mobile phase composed of an aqueous solution of formic acid (0.1 %, v/v) and acetonitrile, pumped with a gradient elution at 30 °C. The proposed method was linear (r² ≥ 0.993) within the concentration ranges of 0.017-5.28 μg mL^-1, 0.066-5.28 μg mL^-1, 0.033-5.28 μg mL^-1 and 0.017-5.28 μg mL^-1 for apixaban, dabigatran, edoxaban and rivaroxaban, respectively, all of them including the expected range of therapeutic concentrations. Overall, intra- and inter-day trueness of quality control samples, including at the lower limit of quantification (LLOQ), varied between -12.98 to 5.79 %, while imprecision was lower than 16.43 %, supporting that the method is accurate and precise in accordance to international guidelines. Recovery and stability were also assessed and allowed the method to be applied in clinical practice, during therapeutic drug monitoring.

An improved extraction protocol for therapeutic dabigatran monitoring using HPLC-MS/MS

A new sample extraction protocol was developed for pharmacokinetic studies of dabigatran with high-performance liquid chromatography separation - electrospray ionization time-of-flight mass spectrometry analysis. After protein precipitation with acetonitrile, free dabigatran and its metabolites are separated into water phase by water-dichloromethane liquid-liquid extraction to purify the sample from proteins and endogenous lipophilic compounds. Chromatographic separation was achieved on an Agilent Zorbax SB-CN column (150 × 4.6 mm, 5 µm)) using 0.1% aqueous solution of formic acid and acetonitrile (80:20) as the mobile phase. Agilent Zorbax SB-CN column was selected to improve sample resolution and to avoided early elution of dabigatran previously seen when using a C18 column. The extended calibration curve was constructed from 5 to 1000 ng/L while precision and accuracy were assessed at four levels across the linear dynamic ranges. Within-run precision was <5.6% and the between-run precision was <3.9%. The method accuracy ranged from 89.8% to 104.4%. The developed method was successfully applied to 30 patient samples to evaluate antithrombotic efficacy and anticoagulant activity of dabigatran following knee endoprosthesis surgery.