Apixaban Plasma Concentration Research Articles

Apixaban plasma concentrations before and after catheter ablation for atrial fibrillation.

Catheter ablation in patients with atrial fibrillation is associated with a transient increase in thromboembolic risk and adequate anticoagulation is highly important. When patients are anticoagulated with apixaban, monitoring of plasma concentrations of the drug is not routinely performed. This study aimed to assess the influence of clinical patient characteristics, concomitant drug treatment and self-reported adherence on apixaban concentrations, and to describe the intra- and inter-individual variability in apixaban concentrations in this group of patients. Method Apixaban concentrations from 141 patients were measured in plasma one week before ablation and two, six and ten weeks after ablation, employing ultra-high performance liquid chromatography coupled with tandem mass spectrometry. In samples not obtained at trough, apixaban concentrations were adjusted to trough levels. Self-reported adherence was registered by means of the 8-item Morisky Medication Adherence Scale before and after ablation. There were statistically significant, positive correlations between apixaban concentrations and increased age, female sex, lower glomerular filtration rate, higher CHA2DS2-VASc score, use of cytochrome P450 3A4 and/or p-glycoprotein inhibitors, and use of amiodarone. Self-reported adherence was generally high. The mean intra-individual and inter-individual coefficients of variation were 29% and 49%, respectively. In patients undergoing catheter ablation for atrial fibrillation, age, sex, renal function, interacting drugs and cerebrovascular risk profile were all associated with altered plasma apixaban concentration. In this group of patients with a generally high self-reported adherence, intra-individual variability was modest, but the inter-individual variability was substantial, and similar to those previously reported in other patient apixaban-treated populations. If a therapeutic concentration range is established, there might be a need for a more flexible approach to apixaban dosing, guided by therapeutic drug monitoring.

Apixaban plasma concentrations in patients with obesity

PurposeRoutine therapeutic drug monitoring of apixaban is currently not recommended but may however be warranted in some situations and for some patient groups to provide better and safer treatment. Due to limited data on apixaban concentrations in different subpopulations, it is still unclear which group of patients could possibly gain from monitoring. The purpose of this study was to examine apixaban exposure in patients with obesity compared with normal-weight patients.MethodsForty patients with obesity (mean BMI 39.4 kg/m2) and 40 controls with normal weight (mean BMI 23.4 kg/m2), treated with apixaban 5 mg twice daily were included. The patients were matched for age, sex, and renal function. Trough and peak apixaban concentrations were measured with LC‒MS/MS methodology.ResultsThe median trough concentrations in patients with obesity (58.7, range 10.7–200.7 ng/ml) were slightly higher than those in patients with normal weight (52.0, range 31.0–150.9 ng/ml) (p < 0.05). Notably, the variability in trough concentration was considerably higher in patients with obesity. Peak concentrations were similar in both groups, with a median of 124.5 ng/ml (range 82.0–277.5) and 113.5 ng/ml (range 75.5–334.6) in patients with obesity and normal weight, respectively.ConclusionApixaban exposure did not vary substantially between obese and normal weight matched controls, implying that general dose adjustments are not required. However, vast interindividual variability was observed in patients with obesity, suggesting that measuring the concentrations could be valuable for specific patients. Further research is needed to identify which specific patients may benefit from this approach.

PB1124 Peak Plasma Concentrations of Apixaban in Children, Adolescents and Young Adults with Different Dosing Regimens Applied

PB1124 Peak Plasma Concentrations of Apixaban in Children, Adolescents and Young Adults with Different Dosing Regimens Applied

Serum or Plasma for Quantification of Direct Oral Anticoagulants?

Background:Direct oral anticoagulants are increasingly replacing vitamin K antagonists for prevention of stroke in patients with atrial fibrillation, partly owing to the lack of a need for routine monitoring. Therapeutic drug monitoring may still be warranted under certain circumstances. It is generally assumed that serum and plasma can be interchangeably used for this purpose. The aim of this study was to investigate possible differences between the serum, citrate-plasma, and ethylenediaminetetraacetic acid (EDTA)-plasma concentrations of apixaban and rivaroxaban in a larger patient group and their relation to factor X measurements.Methods:Plasma and serum samples were drawn during the same venipuncture from patients treated with apixaban or rivaroxaban. Drug levels were measured using ultrahigh-performance liquid chromatography combined with tandem mass spectrometry. Three sample matrices were obtained from 8 healthy volunteers for measurement of factor X antigen and activity.Results:Mean concentrations of apixaban and rivaroxaban were 16.8% and 36.6% higher in serum than in citrate-plasma, respectively (both P < 0.001). The corresponding differences in serum versus EDTA-plasma were 4.5% for apixaban and 13.1% for rivaroxaban (both P < 0.001). Factor X antigen measurements in citrate-plasma, EDTA-plasma, serum with clot activator, and serum without additives yielded comparable results, and factor X activity was significantly higher in serum than in plasma.Conclusions:Apixaban and rivaroxaban concentrations were significantly higher in serum than in plasma. The difference was more pronounced with rivaroxaban and was larger between serum and citrate-plasma than between serum and EDTA-plasma. Higher factor X activity in serum may explain the observed concentration differences. The choice of matrix is, thus, important when interpreting therapeutic drug monitoring results and in research involving analyses of direct oral anticoagulants. The authors recommend citrate-plasma as the preferred matrix.

Apixaban Discontinuation for Invasive Or major Surgical procedures (ADIOS): A prospective cohort study.

Background: Apixaban pharmacokinetic properties and some clinical reports suggest cessation 48 hours prior to surgery is safe, but this has not been demonstrated in a naturalistic setting. We sought to measure the residual apixaban exposure in patients who had apixaban held as part of standard of care perioperative management. Methods: This was a prospective, observational study of patients in whom apixaban plasma concentration and anti-Xa activity were measured while at steady state apixaban dosing and again immediately prior to surgery. Clinical management of cessation and resumption of apixaban was at the discretion of the treating physician. Results: Paired blood samples were provided by 111 patients. Ninety-four percent (104/111) of patients had measured apixaban concentrations of ⩽ 30 ng/mL. Only one patient had a value > 50 ng/mL. The median time between the self-reported last dose and presurgery blood sampling was 76 hours (range 32-158) for those who achieved concentrations ⩽ 30 ng/mL and 59 hours (range 49-86) for those > 30 ng/mL. Measured anti-Xa activity correlated well with apixaban exposure. Clinically significant nonmajor bleeding was reported in one patient at 1 week postsurgery. There was one venous thromboembolic event and one stroke in the perioperative period. Conclusion: In a naturalistic setting with a heterogeneous patient population, apixaban discontinuation for at least 48 hours before a procedure resulted in a clinically insignificant degree of anticoagulation prior to a surgical procedure. ClinicalTrials.gov Identifier: NCT02935751.

Direct Acting Oral Anticoagulants Following Gastrointestinal Tract Surgery.

Direct-acting oral anticoagulants (DOACs) vary in bioavailability and sites of absorption in the gastrointestinal tract (GIT). Data on DOAC use after major GIT surgery are limited. The aim of this case series was to report the impact of surgical resection or bypass of the GIT on rivaroxaban and apixaban peak plasma concentrations. This was a case series of patients who received rivaroxaban or apixaban after GIT surgery, during the period of July 1, 2019, to December 31, 2020. Peak plasma concentrations of rivaroxaban and apixaban were assessed for the expected concentrations. Of the 27 assessed patients, 18 (66.7%) received rivaroxaban, and 9 (33.3%) received apixaban. After rivaroxaban therapy, 4 of 5 patients (80%) who underwent gastrectomy, and 3 of 3 patients (100%) who underwent duodenum and proximal jejunum exclusion had peak plasma concentrations of rivaroxaban lower than the effective range, whereas 11 of 11 patients (100%) who underwent distal bowel or ileostomy had peak rivaroxaban plasma within the effective range. After apixaban therapy, 5 of 6 patients (83.3%) who underwent total or partial gastrectomy achieved effective peak concentrations. All the patients who underwent proximal and distal bowel resection or bypass had peak concentrations of apixaban within the effective range. In conclusion, surgical resection or bypass of the upper GIT could affect DOAC absorption and subsequently peak plasma concentrations. This effect was more observed among rivaroxaban recipients. An injectable anticoagulant or vitamin K antagonist may be preferred if DOAC concentrations cannot be measured after GIT surgery.

A prospective observational study of the rapid detection of clinically-relevant plasma direct oral anticoagulant levels following acute traumatic injury.

In urgent clinical situations, such as trauma, urgent surgery or before thrombolysis, rapid quantification of direct oral anticoagulant plasma drug levels is warranted. Using the ClotPro® analyser, we assessed two novel viscoelastic tests for detection of clinically-relevant plasma drug levels in trauma patients. The ecarin clotting time was used to assess the plasma concentration of dabigatran and Russell´s viper venom clotting time to determine the plasma concentration of direct factor Xa inhibitors. In parallel, plasma concentrations were analysed using plasma-based chromogenic assays. A total of 203 simultaneous measurements were performed.Strong to very strong linear correlations were detected between ecarin clotting time and plasma concentration of dabigatran (r=0.9693), and between Russell´s viper venom clotting time and plasma concentrations of apixaban (r=0.7391), edoxaban (r=0.9251) and rivaroxaban (r=0.8792), all p<0.001. An ecarin clotting time≥189seconds provided 100% sensitivity and 90% specificity for detecting plasma dabigatran concentrations≥50ng.ml-1 . Corresponding Russell´s viper venom clotting time cut-off values were≥136seconds for apixaban (80% sensitivity, 88% specificity), ≥ 168seconds for edoxaban (100% sensitivity, 100% specificity) and≥177seconds for rivaroxaban (90% sensitivity, 100% specificity). Detection of drug levels≥100ng.ml-1 was also investigated: for dabigatran, an ecarin clotting time≥315seconds yielded 92% sensitivity and 100% specificity; while Russell´s viper venom clotting time cut-offs of 191, 188 and 196seconds were calculated for apixaban (67% sensitivity, 88% specificity), edoxaban (100% sensitivity, 75% specificity) and rivaroxaban (100% sensitivity, 91% specificity), respectively. We have demonstrated strong positive correlations between plasma drug levels and clotting time values in the specific ClotPro assays. Cut-off values for detecting clinically-relevant drug levels showed high levels of sensitivity and specificity.

Transitioning hospitalized patients from rivaroxaban or apixaban to a continuous unfractionated heparin infusion: A retrospective review.

To determine a patient's clinical course based on the use of an activated partial thromboplastin time (aPTT) or heparin anti-Xa assay when transitioning from rivaroxaban or apixaban to an unfractionated heparin infusion. A retrospective chart review was conducted to investigate how unfractionated heparin infusions were managed at a tertiary care hospital in the setting of recent apixaban or rivaroxaban administration. Patients were separated into 2 cohorts based on the chosen heparin infusion monitoring assay: heparin anti-Xa or aPTT. The primary composite outcome was total number of bleeding and thrombotic events; the secondary composite outcome was average incidence of heparin infusion holds and rate changes per patient. Data were collected from 76 patients (heparin anti-Xa = 69, aPTT = 7). Due to the limited number of patients within the aPTT cohort, this data was excluded from the analysis, and heparin anti-Xa descriptive statistics were reported without statistical comparisons. In the heparin anti-Xa group, a total of 10 bleeds and 1 thrombus were discovered. Additionally, the average number of infusion holds and rate changes was 0.841 and 2.65 times per patient, respectively, for those patients monitored via heparin anti-Xa assay. In the presence of a recently administered oral anti-Xa anticoagulant, more down-titrations occurred in the initial 6 hours of the heparin infusion when measuring anti-Xa activity, and most up-titrations occurred after 36 hours. Baseline heparin anti-Xa activity may be a useful tool to identify patients with residual plasma concentrations of apixaban and rivaroxaban to help better individualize heparin therapy.

Effects of direct oral anticoagulants on thromboelastographic parameters and fibrin clot properties in patients with venous thromboembolism.

Data concerning the impact of direct oral anticoagulants (DOACs) on the thromboelastography (TEG) indices in venousthromboembolism (VTE) patients are limited. The goal of this study was to compare the impact of DOACs on clot properties measured in whole blood using TEG kaolin test and in plasma obtained from real-life VTE patients. We assessed 53 patients, including 20 on rivaroxaban, 20 on apixaban, and 13 on dabigatran. Using the TEG® 5000, coagulation status was evaluated in whole blood samples, while plasma fibrin clot permeability (Ks) and its susceptibility to lysis (CLT) were assessed in citrated plasma. Plasma concentrations of rivaroxaban (99 [48 - 311] ng/ml) and apixaban (85 [40 - 105] ng/ml) were positively associated with Ks and inversely with CLT, while dabigatran concentrations (71 [39 - 98] ng/ml) correlated positively with Ks. Moreover, Ks was associated with clot formation times (R and K), time to maximum clot strength (TMA), coagulation index (CI) reflecting the overall coagulation status, and whole blood clot lysis time (TEG-CLT). Blood clot lysis index (CL30) was associated with plasma CLT in all patients on DOACs, while TMA correlated with CLT only in patients on apixaban. Higher DOAC concentrations were associated with longer retardation of whole blood clot formation and longer time needed to reach maximum level of its strength as well as with more permeable clots. We concluded that plasma fibrin clot properties correlate with corresponding TEG indices suggesting that TEG might be helpful in providing prognostic information about DOAC influence in VTE patients.

Interindividual Variability of Apixaban Plasma Concentrations: Influence of Clinical and Genetic Factors in a Real-Life Cohort of Atrial Fibrillation Patients.

(1) Background: Prescribing apixaban for stroke prevention has significantly increased in patients with non-valvular atrial fibrillation (NVAF). The ABCB1 genotype can influence apixaban absorption and bioavailability. The aim of the present study was to assess the factors that influence apixaban’s plasma level and to establish if a certain relationship has clinical relevance. (2) Methods: Fifty-three NVAF patients were treated with 5 mg apixaban twice/day (70.0 years, range: 65–77, 60.4% men). Trough and peak plasma concentrations of apixaban were determined by liquid chromatography-tandem mass-spectrometry (LC-MS/MS), and ABCB1 genotyping was performed. (3) Results: Apixaban plasma concentrations varied considerably. They were higher in women than in men (311.2 ng/dL vs. 252.2 ng/dL; p = 0.05) and were lower in patients with heart failure (149.4 ng/dL vs. 304.5 ng/dL; p < 0.01). Creatinine clearance was inversely correlated with the apixaban plasma level (Spearman correlation: r = −0.365; p = 0.007 for trough concentrations). No statistically significant differences between the genotypic groups of ABCB1 rs1045642 and ABCB1 rs4148738 were found in the trough or peak apixaban plasma concentrations. (4) Conclusions: Pharmacokinetic parameters are influenced by several clinical factors of which renal function is the major determinant. Plasma concentrations measured in women had higher values than those measured in men, and heart failure was associated with decreased plasma levels of apixaban.

Using the PCI-IS Method to Simultaneously Estimate Blood Volume and Quantify Nonvitamin K Antagonist Oral Anticoagulant Concentrations in Dried Blood Spots.

Nonvitamin K antagonist oral anticoagulants (NOACs) have emerged as the preferred choice for the treatment of atrial fibrillation (AF). The establishment of a therapeutic range to minimize bleeding and thrombosis is important for personalized treatment of NOACs. The importance of dried blood spots (DBSs) has increased in medical care. An efficient and effective DBS analytical method could facilitate the concentration management of NOACs. The postcolumn infused internal standard (PCI-IS) method was applied to estimate spot volume and quantify dabigatran, rivaroxaban, and apixaban concentrations on DBS cards. The extraction solvent contented 0.1% formic acid and 70% ACN with a successive extraction procedure. Paired DBS and plasma samples from patients undergoing NOAC therapy (n = 269) were used to calculate conversion factors. [13C6]-Rivaroxaban was selected as the PCI-IS. The quantification accuracy for the three NOACs was within 88.9-104.3%. The RSDs of the repeatability and intermediate precision were below 10%. The obtained conversion factors of DBS to plasma concentrations of dabigatran, apixaban, and rivaroxaban were 1.81, 1.59, and 1.31, respectively. Bland-Altman analysis showed that the % differences between predicted and measured plasma concentrations were within a bias of ±20%. The result showed that PCI-IS was an accurate and efficient LC-MS/MS method to simultaneously estimate blood volume and NOAC concentrations on DBS cards. The stability results revealed that the DBS sampling strategy could improve compound stability. The developed method offers a new strategy for the therapeutic drug monitoring of NOACs and may improve the safe use of these drugs.

Safety and Efficacy of Apixaban Versus Enoxaparin/Warfarin in Patients with Extremes of Body Weight: Post-Hoc Analysis of the AMPLIFY Trial

BACKGROUND: Guidelines recommend avoiding direct oral anticoagulants (DOACs) in patients who weigh &gt;120 kg due to limited clinical data in this population. OBJECTIVES: The objective of this post-hoc analysis of the AMPLIFY trial was to evaluate the efficacy, safety, and exposure of apixaban for the treatment of VTE in patients across the following weight categories: ≤ 60 kg, &gt;60 to &lt;100 kg, ≥ 100 to &lt; 120 kg and ≥ 120 kg. METHODS: This analysis evaluated the efficacy (VTE/VTE related deaths) and safety (Major and composite of Major and Clinically Relevant Non-Major [CRNM] bleeds) of apixaban versus enoxaparin/warfarin in patients for the following four body weight categories: ≤ 60 kg, &gt;60 to &lt;100 kg, ≥ 100 to &lt; 120 kg and ≥ 120 kg. Patients were randomized to apixaban or enoxaparin /warfarin and treated for 6 months and were followed up 30 days after the end of the intended treatment period. The exposure of apixaban across the sub-groups of weight was also evaluated. RESULTS: Of the 5356 patients randomized and included in the safety analysis with body weights recorded, there were 473, 3844, 749, and 290 patients in body weight categories ≤ 60 kg, &gt;60 to &lt;100 kg, ≥ 100 to &lt; 120 kg, and ≥ 120 kg, respectively. The rates of VTE/VTE-related death for apixaban versus enoxaparin/warfarin were similar across the sub-groups of weight with relative risks (RR) and 95% confidence intervals (CI) of 0.63 (95% CI: 0.23, 1.72), 0.99 (95% CI: 0.65, 1.50), 0.77 (95% CI: 0.34, 1.72), and 0.20 (95% CI: 0.02, 1.72) for ≤ 60 kg, &gt;60 to &lt;100 kg, ≥ 100 to &lt; 120 kg, and ≥ 120 kg, respectively (treatment by weight interaction P-value = 0.44). There was a reduction in Major Bleeding events in the &gt;60 to &lt;100 kg sub-group on apixaban compared to enoxaparin/warfarin with RR=0.41 (95% CI; 0.21, 0.77). Due to the low numbers of Major Bleeding events (apixaban: 0/377, enoxaparin/warfarin: 7/372), the RR in the subgroup of weight ≥ 100 to &lt; 120 kg was not estimable. The RRs for ≤ 60 kg, and ≥ 120 kg weight sub-groups were 0.15 (95% CI: 0.02, 1.15), and 0.34 (95% CI: 0.04, 3.22), respectively. For the composite end-point of Major and CRNM bleeds, apixaban-treated patients had less events compared to enoxaparin/warfarin-treated patients across sub-groups of weight [RR of 0.46 (95% CI: 0.24, 0.89) for ≤ 60 kg, RR of 0.49 (95% CI: 0.38, 0.63) for &gt;60 to &lt;100 kg, RR of 0.30 (95% CI: 0.16, 0.58) for ≥ 100 to &lt; 120 kg, and RR of 0.28 (95% CI: 0.12, 0.66) for ≥ 120 kg weight categories (treatment by weight interaction P-value = 0.36)]. A total of 281 patients had apixaban plasma concentrations measured. There was a small non-clinically significant decrease (&lt;30%) in the median predicted exposure across weight sub-groups (2990, 2734, 2239 and 2006 ng*hr/ml in the ≤ 60 kg, &gt;60 to &lt;100 kg, ≥ 100 to &lt; 120 kg and ≥ 120 kg weight categories, respectively). The exposure range was similar among weight categories with overlapping quartiles. CONCLUSION: In this post-hoc analysis, the safety and efficacy of apixaban in patients with extremes of body weight are consistent with the main results of the AMPLIFY trial. Across sub-groups of body weight including extremes of body weight, apixaban compared with enoxaparin/warfarin resulted in similar rates of recurrent VTE/VTE-related death, and reductions in the rates of the composite of Major and CRNM bleeds. There were also no clinically significant differences in apixaban exposure in patients with extremes of body weight compared to those in the &gt;60 to &lt;100 kg weight category. Disclosures Lee: Pfizer Inc.: Employment, Equity Ownership. Pan:Pfizer: Employment. Byon:Pfizer: Employment, Equity Ownership. Ilyas:Pfizer: Employment, Equity Ownership.

P4752Apixaban 2.5 mg twice daily is effective and safe for patients with atrial fibrillation and combinations of advanced age, low body weight, and elevated creatinine: insights from ARISTOTLE

Abstract Background In ARISTOTLE, patients with atrial fibrillation and ≥2 dose-reduction criteria [age ≥80 years, weight ≤60 kg, and creatinine ≥1.5 mg/dL (133 μmol/L)] were randomized to apixaban 2.5 mg twice daily (b.i.d) or warfarin. Purpose To determine whether the apixaban dose adjustment in ARISTOTLE resulted in similar efficacy and safety compared to warfarin. Methods The effects of apixaban 2.5 mg b.i.d versus warfarin on stroke or systemic embolism, major bleeding and death in ARISTOTLE patients with ≥2 dose-reduction criteria were compared with the effects of apixaban 5 mg b.i.d in patients with 0 or 1 dose-reduction criterion. Results Of 751 (4.1%) patients with ≥2 dose-reduction criteria, 386 were assigned to apixaban 2.5 mg b.i.d and 365 to warfarin. Compared to patients with 0 or 1 dose reduction criteria (n=17,322), these patients had a higher risks of stroke/systemic embolism (HR =1.78; 95% CI [1.24–2.57]), major bleeding (HR =1.73; 95% CI [1.28–2.32]) and death (HR=3.21; 95% CI [2.69–3.83]), irrespective of whether they were assigned to apixaban or warfarin. The benefits of apixaban 2.5 mg b.i.d compared with warfarin on stroke or systemic embolism, major bleeding, and death in patients with ≥2 dose-reduction criteria were consistent with that of apixaban 5 mg b.i.d in patients with either 0 or 1 dose-reduction criteria (Figure). Conclusions While they are at higher overall risk, patients with appropriate dose reduction criteria have consistent benefits with apixaban 2.5 mg b.i.d. over warfarin. Additional analyses investigating the relationship between apixaban dose and both apixaban plasma concentrations and levels of thrombosis biomarkers are underway. Acknowledgement/Funding Bristol-Myers Squibb and Pfizer, Inc.

Unexpected excessive apixaban exposure: case report of a patient with polymorphisms of multiple apixaban elimination pathways

BackgroundApixaban effectively lowers the risk of ischemic stroke and systemic embolism in patients with non-valvular atrial fibrillation. Systemic exposure to a given apixaban dose depends on multiple clearance pathways. Though routine quantification of direct oral anticoagulants (DOACs) in neurological emergency situations has not been widely established, suspected associations of DOAC peak concentrations with bleeding events and DOAC trough concentrations with efficacy and safety suggest that such information might support clinical decision making.Case presentationWe describe the case of a 75 year-old woman with atrial fibrillation maintained on apixaban who was admitted due to suspected acute stroke. Clinical work-up did not confirm ischemic or hemorrhagic stroke but routine quantification of apixaban revealed an excessively high apixaban plasma concentration (~ 3 h after the last drug intake: 1100 ng/ml (expected range: 91–321 ng/ml); ~ 12 h after drug intake: 900 ng/ml (expected range: 41–230 ng/ml)) and a substantially prolonged elimination half-life (~ 31 h). The corresponding apixaban concentration-to-dose ratio was 9900 (ng/ml)/(mg/kg/d) and 8100 (ng/ml)/(mg/kg/d), respectively (expected range: 249–463 (ng/ml)/(mg/kg/d)). Renal function was only moderately impaired (creatinine 1.36 mg/dl (0.5–1.1 mg/dl), creatinine clearance 40 ml/min). Genotype analyses revealed that the patient was a CYP3A5*3/*3 non-expressor, a heterozygous carrier of the ABCG2 c.421C/A alleles, and a homozygous carrier of ABCB1 c.2677 T/T and ABCB1 c.3435 T/T. In the absence of known drug interactions explaining apixaban clearance impairment, excessive apixaban concentrations were most probably caused by moderate renal impairment combined with multiple functional polymorphisms of apixaban clearance pathways.ConclusionsThis case suggests that concurrent genetic polymorphisms can impair multiple apixaban elimination pathways and thus substantially increase its exposure.

Apixaban: A Clinical Pharmacokinetic and Pharmacodynamic Review.

Apixaban is an oral, direct factor Xa inhibitor that inhibits both free and clot-bound factor Xa, and has been approved for clinical use in several thromboembolic disorders, including reduction of stroke risk in non-valvular atrial fibrillation, thromboprophylaxis following hip or knee replacement surgery, the treatment of deep vein thrombosis or pulmonary embolism, and prevention of recurrent deep vein thrombosis and pulmonary embolism. The absolute oral bioavailability of apixaban is ~ 50%. Food does not have a clinically meaningful impact on the bioavailability. Apixaban exposure increases dose proportionally for oral doses up to 10 mg. Apixaban is rapidly absorbed, with maximum concentration occurring 3–4 h after oral administration, and has a half-life of approximately 12 h. Elimination occurs via multiple pathways including metabolism, biliary excretion, and direct intestinal excretion, with approximately 27% of total apixaban clearance occurring via renal excretion. The pharmacokinetics of apixaban are consistent across a broad range of patients, and apixaban has limited clinically relevant interactions with most commonly prescribed medications, allowing for fixed dosages without the need for therapeutic drug monitoring. The pharmacodynamic effect of apixaban is closely correlated with apixaban plasma concentration. This review provides a summary of the pharmacokinetic, pharmacodynamic, biopharmaceutical, and drug–drug interaction profiles of apixaban. Additionally, the population-pharmacokinetic analyses of apixaban in both healthy subjects and in the target patient populations are discussed.

Pharmacokinetics of anticoagulants apixaban, dabigatran, edoxaban and rivaroxaban in elderly Japanese patients with atrial fibrillation treated in one general hospital

Steady-state plasma concentrations of anticoagulants and the time since the previous administration in mainly outpatients with atrial fibrillation administered standard or reduced doses were analyzed for 110 elderly Japanese subjects (mean age, 76 years) treated with apixaban (2.5 or 5.0 mg twice daily), dabigatran etexilate (110 or 150 mg twice daily), edoxaban (30 or 60 mg once daily) or rivaroxaban (10 or 15 mg once daily) at one general hospital.The pharmacokinetics in patients treated with standard and reduced doses of the four anticoagulants using liquid chromatography-tandem mass spectrometry was compared with the concentration ranges estimated using physiologically based pharmacokinetic modeling. Reduced doses of anticoagulants resulted in relatively small pharmacokinetic variations compared with the standard dose.Statistical analyses revealed that renal impairment is likely not the sole determinant factor for high plasma concentrations of apixaban, dabigatran, edoxaban and rivaroxaban.Patients with atrial fibrillation should be treated with the correct doses of oral anticoagulants as specified in the package inserts (e.g. reduced doses for elderly patients, patients with low body weights and in combination with P-glycoprotein inhibitor drugs) to avoid excessive or insufficient doses of direct oral anticoagulants.

Anti-Xa Oral Anticoagulant Plasma Concentration Assay in Real Life: Rivaroxaban and Apixaban Quantification in Emergency With LMWH Calibrator.

Oral anti-Xa inhibitors have demonstrated noninferiority to vitamin K antagonists (VKAs) for the prevention of stroke in patients with atrial fibrillation and recurrent venous thromboembolism. They are associated with a decrease in major bleeding. In contrast with VKA, no coagulation monitoring is required. However, in clinical practice, determination of drug concentration is sometimes necessary. The objective of this study was to evaluate a low-molecular-weight heparin (LMWH) calibrated anti-Xa assay for the quantification of rivaroxaban and apixaban plasma concentration in emergency. The anti-Xa plasma concentration of rivaroxaban and apixaban were measured in emergency in 210 patients using STA anti-Xa liquid assay. For each plasma concentration <150 ng/mL of rivaroxaban or apixaban, an anti-Xa assay calibrated with LMWH was performed. We demonstrated a significant correlation between LMWH anti-Xa activity and rivaroxaban ( R2 = 0.947) or apixaban ( R2 = 0.959) concentration and a significant correlation between rivaroxaban and apixaban plasma concentration ( R2 = 0.972). A LMWH anti-Xa activity <0.50 IU/mL could exclude a plasma concentration of rivaroxaban and apixaban >30 ng/mL and indicate the feasibility of invasive procedure. Conclusion and Relevance: In the absence of a specific test, LMWH-calibrated anti-Xa assay could be used to determine the presence and evaluate the plasma concentration of oral anti-Xa inhibitors. However, these initial findings require confirmation using other chromogenic calibrated oral anti-Xa assays.

Evaluation of the single-dose pharmacokinetics and pharmacodynamics of apixaban in healthy Japanese and Caucasian subjects.

PurposeThis double-blind, placebo-controlled, intra-subject, dose-escalation study assessed single-dose safety, pharmacokinetics, and pharmacodynamics of apixaban in healthy Japanese and Caucasian subjects.Subjects and methodsSixteen healthy male Japanese and sixteen healthy male Caucasian subjects, matched for age, weight, and smoking status were randomized to receive four sequential single oral doses of either apixaban (2.5, 10, 25, and 50 mg) or matched placebo. Doses were separated by a ≥5-day washout. Blood samples were collected for the determination of apixaban plasma concentration, clotting times (international normalized ratio [INR], activated partial thromboplastin time, and modified prothrombin time [mPT]), and ex vivo thrombin generation (TG). Urine samples were collected for the analysis of apixaban concentration.ResultsAscending single doses of apixaban 2.5–50 mg were safe and well tolerated by all subjects. Apixaban exposure increased the dose proportionally up to 10 mg. Apixaban reached maximum concentrations (Cmax) 3–4 h postdose, with mean Cmax ranging from 52.5–485.0 to 44.8–494.3 ng/mL in Japanese and Caucasian subjects. The mean half-life was ~8 and ~13 h and the renal clearance was 1.1 and 0.8 L/h in Japanese and Caucasian subjects, respectively. Pharmacodynamic assessments were similar between ethnic groups, with comparable dose-related prolongation of INR and mPT and inhibition of TG.ConclusionAscending single doses of apixaban over a 20-fold dose range were safe and well tolerated in Japanese and Caucasian subjects in this study. The consistency between pharmacokinetic and pharmacodynamic measures in Japanese and Caucasian subjects indicates that apixaban may be administered as a fixed dose with no need for adjustment in Japanese patients.

A study on indices of apixaban anticoagulation: A single-center prospective study

BackgroundDepending on the characteristics of patients, the blood concentration of apixaban can unexpectedly increase, possibly leading to bleeding events. Anti-FXa activity reflects the apixaban blood concentration; however, measurement of this activity is both time-consuming and expensive. The current study aimed to evaluate the usefulness of routinely measured coagulation indices as future indicators of the efficacy and safety of apixaban. MethodsEighteen nonvalvular atrial fibrillation patients administered apixaban (average, 52.5 days) were prospectively enrolled in our hospital. The prothrombin time (PT) and the activated partial thromboplastin time (APTT) were measured by using the Coagpia® Reagent kits. ResultsThe PT and the APTT increased significantly after the administration of apixaban (PT: p < 0.001, APTT: p < 0.001). While the apixaban plasma concentration by evaluating anti-FXa activity was not significantly correlated with the APTT after administration of apixaban, the concentration closely correlated with the PT (β = 0.765, p < 0.001) and the percentage change in the PT from before and after the administration of apixaban (β = 0.650, p = 0.005). ConclusionThe usefulness of routinely monitoring PT in patients administered apixaban during the ordinary clinical medicine should be investigated further by large clinical trials.

Influence of ABCB1 and CYP3A5 gene polymorphisms on pharmacokinetics of apixaban in patients with atrial fibrillation and acute stroke.

IntroductionDifficulties in non-vitamin K anticoagulant (NOAC) administration in acute stroke can be associated with changes in pharmacokinetic parameters of NOAC such as biotransformation, distribution, and excretion. Therefore, obtaining data on pharmacokinetics of NOAC and factors that affect it may help develop algorithms for personalized use of this drug class in patients with acute cardioembolic stroke.Patients and methodsPharmacokinetics of apixaban in patients with acute stroke was studied earlier by Kryukov et al. The present study enrolled 17 patients with cardioembolic stroke, who received 5 mg of apixaban. In order to evaluate the pharmacokinetic parameters of apixaban, venous blood samples were collected before taking 5 mg of apixaban (point 0) and 1, 2, 3, 4, 10, and 12 hours after drug intake. Blood samples were centrifuged at 3000 rpm for 15 minutes. Separate plasma was aliquoted in Eppendorf tubes and frozen at −70°C until analysis. High-performance liquid chromatography mass spectrometry analysis was used to determine apixaban plasma concentration. Genotyping was performed by real-time polymerase chain reaction. CYP3A isoenzyme group activity was evaluated by determining urinary concentration of endogenous substrate of the enzyme and its metabolite (6-β-hydroxycortisol to cortisol ratio). Statistical analysis was performed using SPSS Statistics version 20.0. The protocol of this study was reviewed and approved by the ethics committee; patients or their representatives signed an informed consent.ResultsABCB1 (rs1045642 and rs4148738) gene polymorphisms do not affect the pharmacokinetics of apixaban as well as CYP3A5 (rs776746) gene polymorphisms. Apixaban pharmacokinetics in groups with different genotypes did not differ statistically significantly. Correlation analysis showed no statistically significant relationship between pharmacokinetic parameters of apixaban and the metabolic activity of CYP3A.ConclusionQuestions such as depending on genotyping results for apixaban dosing and implementation of express genotyping in clinical practice remain open for NOACs. Large population studies are required to clarify the clinical significance of genotyping for this drug class.