International Normalized Ratio Is Significantly Elevated With Rivaroxaban and Apixaban Drug Therapies: A Retrospective Study

Apixaban-Associated Intracranial Hemorrhage in a Patient With Elevated International Normalized Ratio

Apixaban has been associated with prolongation of the international normalized ratio (INR), but data surrounding the extent of elevation and its clinical significance are limited. Due to interaction between apixaban and the prothrombin assay, elevations in INR in patients receiving apixaban are common and not always grounds for concern. However, in high risk patients, elevations can represent a need for closer monitoring. This case summarizes an 82-year-old woman with a history of atrial fibrillation and left middle cerebral artery strokes with no residual deficits. She presented with right-sided hemiparesis and aphasia and underwent a mechanical thrombectomy with TICI 2b recanalization of a left M1 occlusion. Post-thrombectomy, she was found to have a left atrial thrombus and 10 days later was started on apixaban 5 mg twice daily. On the fourth day of apixaban therapy, she experienced an INR increase to 2.3, prompting initiation of a vitamin K challenge for nutritional deficiency. Despite initial improvement, her INR increased to 2.7 a week after apixaban was initiated, coinciding with a decline in mental status and an apixaban peak level of 435.6 ng/mL (reference range 91-321 ng/mL). A computed tomography (CT) scan of her head showed new intracranial hemorrhage in the area of her previous infarction, prompting apixaban reversal with andexanet alfa. Unfortunately, the patient expired. This case report highlights the importance and difficulty in performing therapeutic drug monitoring in patients receiving oral anti-factor Xa inhibitors, revealing a downside to administration of high-risk medications that do not have readily available monitoring.

Elevated International Normalized Ratio and Mortality in Hospitalized Patients Treated with Direct Oral Anticoagulants

BACKGROUND

Direct oral anticoagulants (DOACs) are associated with a prolongation of the prothrombin time and an increased international normalized ratio (INR). The clinical significance of these changes is unclear. This study aimed to examine the association between an elevated INR on admission and in-hospital death and long-term survival in patients treated with DOACs.

METHODS

Data were retrospectively retrieved from records of hospitalized patients at the Sheba Medical Center between November 2008 and July 2023. Patients were selected based on DOAC treatment, coagulation profile, and INR test done within 48 hours of hospitalization. The outcomes were in-hospital mortality and mortality in the year following hospitalization.

RESULTS

The study included 11,399 hospitalized patients treated with DOACs. Patients with elevated INR had a 180% higher risk of in-hospital mortality (adjusted odds ratio 2.80; 95% confidence interval, 2.30-3.39) and a 57% increased risk of death during the following year (adjusted hazard ratio 1.57; 95% confidence interval, 1.44-1.71). Similar results were observed in subgroup analyses for each DOAC.

CONCLUSIONS

An elevated INR on admission is associated with a higher risk for in-hospital death and increased risk for mortality during the first year following hospitalization in hospitalized patients treated with DOACs. This highlights that elevated INR levels in patients on DOACs should not be dismissed as laboratory variations due to DOAC treatment, as they may serve as a prognostic marker.

Challenges to Laboratory Monitoring of Direct Oral Anticoagulants

Direct oral anticoagulants (DOACs) exert anticoagulation effect by directly inhibiting Factor Xa (rivaroxaban, apixaban, and edoxaban) or thrombin (dabigatran). Though DOACs are characterized by fixed-dose prescribing and generally do not require routine laboratory drug-level monitoring (DLM), circumstances may arise where the DLM may aid in clinical decision-making, including DOAC dose adjustment, anticoagulant class change, or decisions to withhold or administer reversal agents. We review the current literature that describes high-risk patient groups in which DLM may be beneficial for improved patient anticoagulation management and stewardship. The review also summarizes the limitations of conventional coagulation testing and discuss the emerging utility of quantitative methods for routine and rapid emergent evaluation of DOAC drug levels-in particular, the Anti-Xa activity to detect Factor Xa Inhibitors (rivaroxaban, apixaban, and edoxaban). Both technical and regulatory barriers to widespread DLM implementation are limiting factors to further clinical research that must be overcome, in order to propose universal DOAC DLM strategies and provide clinical-laboratory correlation to formally classify high-risk patient groups.

A Case of Symptomatic Supratherapeutic International Normalized Ratio on Rivaroxaban

Rivaroxaban is a direct oral anticoagulant that works by inhibiting factor Xa. Direct anticoagulants have largely replaced direct vitamin K inhibitors (VKAs) due to the decreased risk of major hemorrhages and the lack of need for regular monitoring and dose adjustments. However, there have been multiple reports of elevated international normalized ratio (INR) and bleeding incidents in patients on rivaroxaban, which brings into question the potential need for monitoring. We report a case of an INR of 4.8 in a rivaroxaban-naïve patient who presented with gastrointestinal bleeding and a significant drop in hemoglobin four days after starting rivaroxaban. We present possible pharmacologic explanations. We propose the idea that specific subgroups of patients may be at risk for true INR elevations and may benefit from routine monitoring of their INR while on rivaroxaban.

Prothrombin Time-International Normalized Ratio Predicts the Outcome of Atrial Fibrillation Patients Taking Rivaroxaban

Background: Although direct oral anticoagulants (DOACs) for patients with atrial fibrillation (AF) are considered to be safe, over or under anticoagulation and increased bleeding or thromboembolic risk are still considered individually. We aimed to investigate whether there is an association between prothrombin time and international normalized ratio (PT-INR) or activated partial thromboplastin time (aPTT) ratio, and the risks of ischemic stroke/systemic embolism (IS/SE) and major bleeding among AF patients taking rivaroxaban or dabigatran. Methods: This multi-center cohort study in Taiwan included 3192 AF patients taking rivaroxaban and 958 patients taking dabigatran for stroke prevention where data about PT-INR and aPTT were available. Results: For patients treated with rivaroxaban, a higher INR level was not associated with a higher risk of major bleeding compared to an INR level < 1.1. The risk of IS/SE was lower for patients having an INR ≥ 1.5 compared to those with an INR < 1.1 (aHR:0.57; [95%CI: 0.37−0.87]; p = 0.01). On-label dosing of rivaroxaban and use of digoxin were independent factors associated with an INR ≥ 1.5 after taking rivaroxaban. For patients taking dabigatran, a higher aPTT ratio was not associated with a higher risk of major bleeding. The risk of IS/SE was lower for patients having an aPTT ratio of 1.1−1.2 and 1.3−1.4 than those with an aPTT ratio < 1.1. Conclusions: In AF patients, rivaroxaban with an INR ≥ 1.5 was associated with a lower risk of IS/SE. PT-INR or aPTT ratios were not associated with bleeding events for rivaroxaban or dabigatran. INR may help predict the outcome of AF patients who take rivaroxaban.

Preoperative evaluation of coagulation status in neuromodulation patients

OBJECTIVE

The incidence of hemorrhage in patients who undergo deep brain stimulation (DBS) and spinal cord stimulation (SCS) is between 0.5% and 2.5%. Coagulation status is one of the factors that can predispose patients to the development of these complications. As a routine part of preoperative assessment, the authors obtain prothrombin time (PT), partial thromboplastin time (PTT), and platelet count. However, insurers often cover only PT/PTT laboratory tests if the patient is receiving warfarin/heparin. The authors aimed to examine their experience with abnormal coagulation parameters in patients who underwent neuromodulation.

METHODS

Patients who underwent neuromodulation (SCS, DBS, or intrathecal pump implantation) over a 9-year period and had preoperative laboratory values available were included. The authors determined abnormal values on the basis of a clinical protocol utilized at their practice, which combined the normal ranges of the laboratory tests and clinical relevance. This protocol had cutoff values of 12 seconds and 39 seconds for PT and PTT, respectively, and < 120,000 platelets/μl. The authors identified risk factors for these abnormalities and described interventions.

RESULTS

Of the 1767 patients who met the inclusion criteria, 136 had abnormal preoperative laboratory values. Five of these 136 patients had values that were misclassified as abnormal because they were within the normal ranges at the outside facility where they were tested. Fifty-one patients had laboratory values outside the ranges of our protocol, but the surgeons reviewed and approved these patients without further intervention. Of the remaining 80 patients, 8 had known coagulopathies and 24 were receiving warfarin/heparin. The remaining 48 patients were receiving other anticoagulant/antiplatelet medications. These included apixaban/rivaroxaban/dabigatran anticoagulants (n = 22; mean ± SD PT 13.7 ± 2.5 seconds) and aspirin/clopidogrel/other antiplatelet medications (n = 26; mean ± SD PT 14.4 ± 5.8 seconds). Eight new coagulopathies were identified and further investigated with hematological analysis.

CONCLUSIONS

New anticoagulants and antiplatelet medications are not monitored with PT/PTT, but they affect coagulation status and laboratory values. Although platelet function tests aid in a subset of medications, it is more difficult to assess the coagulation status of patients receiving novel anticoagulants. PT/PTT may provide value preoperatively.

Elevated International Normalized Ratio Due to Apixaban in Patient With End-Stage Renal Disease on Hemodialysis

Apixaban is known to prolong international normalized ratio (INR) per some observational and in vitro studies. In patients with elevated INR secondary to apixaban use, median INR of 1.4-1.7 has been reported. Extreme elevation in INR is rare with apixaban. In patients with end-stage renal disease (ESRD) on hemodialysis (HD), there are no labeled indications for apixaban use; however, there are some pharmacokinetic data supporting its use in such patients.

We present a case of a 68-year-old Hispanic man with ESRD who presented to the emergency room (ER) with INR of 27.42. INR testing was done as a part of routine workup in rehabilitation facility. Medication list was reviewed and included apixaban 2.5 mg twice daily which was recently started for postoperative thromboprophylaxis. INR testing was repeated for confirmation in ER and was reported as >18.5 and prothrombin time >200 seconds. His liver function tests were stable as compared to baseline testing five days ago with normal bilirubin, low normal transaminases, and mild hypoalbuminemia. The patient didn’t have any active bleeding. An elevation of INR to >20 with apixaban is a rare event. No other factors including patient characteristics, laboratory results, co-existing conditions, or other medications except the direct oral anticoagulant (DOAC) were found to be responsible for elevated INR. Liver cirrhosis or vitamin K deficiency as cause for INR elevation was ruled out as the baseline INR was normal prior to starting apixaban, liver function tests were stable and INR normalized again shortly after discontinuing the medication. Plasma concentration of DOACs has been found to be correlating with the INR according to a pharmacokinetic study which potentially means that the high INR likely was secondary to high serum concentration of apixaban in this patient. However, INR monitoring is not recommended for monitoring anticoagulant activity of DOACs. As of note, renal clearance accounts for 27% of apixaban clearance.

Pharmacokinetic studies have concluded that half dose apixaban, i.e., 2.5 mg twice daily in patients on hemodialysis (dose used in this case) results in drug exposure similar to that of the standard dose of 5 mg twice daily in patients with preserved renal function. Future studies are necessary to address questions about safety of DOACs in patients with ESRD, further elucidate the clinical significance of such high INR values associated with DOACs, and establish appropriate management guidelines. Andexanet alfa has since been approved for apixaban reversal in patients with life-threatening bleeding; however, would not be indicated in such cases when there is no evidence of bleeding.

Anticoagulation Monitoring in the Intensive Care Unit

Patients with critical illness often display variable hypo- and hypercoagulable sequalae requiring intense monitoring and anticoagulation pharmacotherapy to prevent or treat inappropriate clot formation. It is imperative to understand the various stages of the clotting cascade and where each pharmacotherapy agent exerts its therapeutic effect. Common coagulation tests are utilized to monitor the areas of the clotting cascade and the effects that anticoagulant pharmacotherapy exhibits. Many novel coagulation tests are also in development. The purpose of this narrative review is to evaluate commonly utilized coagulation tests that monitor anticoagulation while in the intensive care unit.

Utilization of apixaban anti-Xa levels in transition from apixaban to warfarin in a patient with chronic renal dysfunction

DISCLAIMER

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

The effect of apixaban on anti-factor Xa (anti-Xa) assays and international normalized ratio (INR) complicates transitions between anticoagulant agents. When switching from apixaban to warfarin, the recommendation is to begin both a parenteral anticoagulant and warfarin at the time of the next apixaban dose and to discontinue the parenteral agent when INR is in an acceptable range. This proves challenging in renal dysfunction, as continued presence of apixaban contributes to both a prolonged effect on the INR and continued therapeutic levels of anticoagulation.

SUMMARY

This case describes the transition of apixaban to warfarin in a patient with acute on chronic kidney disease and recent deep vein thrombosis, utilizing chromogenic apixaban anti-Xa assays to assess the level of anticoagulation and avoid unnecessary parenteral anticoagulation.

CONCLUSION

Utilization of apixaban anti-Xa levels aided in the transition from apixaban to warfarin in a patient with chronic renal failure and avoided need for parenteral bridging therapy.

Effect of an Elevated Preoperative International Normalized Ratio on Transfusion and Complications in Primary Total Hip Arthroplasty with the Enhanced Recovery after Surgery Protocol

Objective

To verify whether an elevated preoperative international normalized ratio (INR) increases transfusion and complications independently in primary total hip arthroplasty (THA) with the management of an enhanced recovery after surgery (EARS) protocol.

Methods

We retrospectively reviewed the database of adults who underwent primary THA between 2014 and 2018 by the same surgeon. A total of 552 patients were assigned into three groups by preoperative INR class: INR ≤ 0.9, 0.9 < INR < 1.0, and INR ≥ 1.0. We regarded transfusion within 90 days during the same hospitalization as the primary outcome. We also included perioperative blood loss, maximum Hb drop, postoperative anaemia requiring medicine, and length of hospital stay (LOS) during the same hospitalization in the study. Complications and reoperation at 90 days and mortality at 90 days and 12 months were also included in the study. Univariable analyses were utilized to compare baselines and outcomes among the three groups. Multivariate logistic regressions were used to adjust for differences at baseline among the groups.

Results

All patients had an INR < 1.5 preoperatively and were managed with the ERAS protocol. Among them, 93 (16.8%) patients had INR ≤ 0.9, 268 (48.6%) patients had 0.9 < INR < 1.0, and 191 (34.6%) patients had INR ≥ 1.0. In the univariable analyses, as the INR increased, the transfusion rates increased from 1.08% for INR ≤ 0.9, to 1.12% for 0.9 < INR < 1.0 and to 5.76% for INR ≥ 1.0 (P < 0.05). The overall complication rate increased from 10.8% for INR ≤ 0.9, to 16.4% for 0.9 < INR < 1.0, and to 22.5% for INR ≥ 1.0 (P < 0.05). The length of stay (LOS) in the INR ≥ 1.0 group was 5.7 ± 2.2 days, which was significantly longer than that in the INR ≤ 0.9 group (4.7 ± 1.6 days, P = 0.000) and 0.9 < INR < 1.0 group (5.1 ± 2.0 days, P = 0.007). No statistical significance was detected among the groups regarding blood loss, maximum Hb drop, or the incidence of postoperative anaemia that required medicine. There was no significant difference in reoperation or mortality among the groups. When controlling for demographic and comorbidity characteristics, there was no statistically significant difference in the odds of transfusion during the same hospitalization or overall complications at 90 days among the groups (P > 0.05).

Conclusions

Elevated preoperative INR cannot increase transfusion or complication rates independently in primary THA with the management of the ERAS protocol. With the improvement in the ERAS protocol and the use of tranexamic acid (TXA), an INR < 1.5 is still a conventional safe threshold for THA surgery.

Rivaroxaban versus low-molecular weight heparin plus warfarin prevents portal vein system thrombosis after splenectomy and pericardial devascularization: A randomized clinical trial

This study aimed to evaluate the safety and efficacy of rivaroxaban in preventing portal vein system thrombosis (PVST) in patients with liver cirrhosis after splenectomy and pericardial devascularization. 70 cirrhotic patients undergoing splenectomy and pericardial devascularization were randomly assigned to rivaroxaban treatment (n=35) or low-molecular weight heparin (LMWH) plus warfarin treatment (n=35) for 30 days in this randomized controlled trial. The primary endpoint is the PVST formation. Ultrasound doctors and radiologists were blinded to the randomization results. Both groups received routine outpatient inspection every month and were followed for one year. 17 patients (48.6 %) in rivaroxaban group developed PVST, compared with 27 patients (77.1 %) in LMWH plus warfarin group (P=0.025). The incidence of PVST during the first year postoperation was significantly lower in rivaroxaban group than in LMWH plus warfarin group (F=7.901, P=0.006). The intra-group comparisons versus baseline showed the liver function improved from POD 21 to POM 1, and coagulation function improved from POM 2, in rivaroxaban group. In contrast, the liver function improved from POM 1 to POM 2, and coagulation function improved from POM 4, in LMWH plus warfarin group. The prophylactic use of rivaroxaban significantly decreases the incidence of PVST after splenectomy and pericardial devascularization in cirrhotic patients compared to LMWH plus warfarin treatment. Besides, rivaroxaban treatment was safe and effective and associated with better liver and coagulation functions improvement than LMWH plus warfarin treatment.

Tranexamic Acid Combined with Compression Bandage Following Total Knee Arthroplasty Promotes Blood Coagulation: A Retrospective Analysis

Objective

This paper included a retrospective review of the effect of tranexamic acid (TXA) combined with pressure bandaging on hemostasis of patients who received a unilateral total knee arthroplasty (TKA) from 2017 to 2019.

Methods

A total of 197 patients undergoing TKA were chosen to be classified into 2 groups, the compression bandage control group and compression bandage combined with TXA observation group. The patients received blood routine examination when they were in the 1st, 3rd, and 6th days of before and postoperation. Some parameters, such as hemoglobin (Hb), C-reactive protein (CRP), D-dimer value, fibrinogen, prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), international normalized ratio (INR), and erythrocyte sedimentation rate (ESR), were also investigated.

Results

In our research, the mean age was 66.54 ± 7.95 years. No difference was found in patient sex (P = 0.876) and age (P = 0.749) between groups. No differences were found in the levels of Hb, fibrinogen, TT, and INR between the 2 groups at each period (P > 0.05). The difference of PT was significantly different on the 1st day (P = 0.011), 3rd day (P = 0.010), and 6th day (P = 0.004) after surgery. Besides, the changes in APTT in observation group were clearly higher compared with the control group on the 3rd day (P = 0.001) and 6th day (P = 0.001). On the 3rd and 6th days after operation, the CRP level of the two groups increased continuously, and the CRP level was significantly higher in the observation group in comparison with the control group (P = 0.008, P = 0.010). On 1st and 3rd days after surgery, compared to the control group, the D-dimer level of patients in the observation group was distinctly fewer (P = 0.001, P = 0.027).

Conclusion

TXA combined with compression bandage is a potential option for the reduction of bleeding after TKA.

Slightly elevated international normalized ratio predicts bleeding episodes in patients treated with direct oral anticoagulants

Introduction

Patients treated with direct oral anticoagulants (DOACs) are at increased bleeding risk. It is therefore of increasing interest to identify predictors of bleeding episodes to increase safety during treatment with DOACs.

Methods

This retrospective cohort study systematically reviewed medical records of 235 patients treated with either apixaban, rivaroxaban or dabigatran for non-valvular atrial fibrillation or venous thromboembolism and collected data on the international normalized ratio (INR) and all bleeding episodes.

Results

INR ≥ 1.5 was significantly associated with increased risk of minor and major bleeding events in patients treated with direct factor Xa inhibitors. This association was not present in patients treated with dabigatran. However, a high negative predictive value was identified for INR < 1.5 for all drugs. The relative risks of bleeding episodes in patients with INR ≥ 1.5 and INR < 1.5 were 5.1 and 0.20, respectively.

Conclusions

Our results demonstrate a strong correlation between INR and risk of bleeding episodes during DOAC treatment. INR < 1.5 was a strong negative predictor for low bleeding risk independent of indication or choice of drug, and INR ≥ 1.5 was associated with increased risk of bleeding episodes in patients treated with direct factor Xa-inhibitors.

Pain in the hip: Spontaneous retroperitoneal hemorrhage in an elderly patient on apixaban

As many as 5% of patients using oral anticoagulants suffer from a major bleeding event annually. Spontaneous retroperitoneal hemorrhage is a rare but serious complication, with a mortality rate as high as 20%. Oral anticoagulants were responsible for 2.83 million office visits per quarter in 2014 and use is increasing, therefore, rapid recognition of life threatening complications is critical. We present a case of an 86-year-old female taking apixaban for atrial fibrillation who presented with right hip pain upon standing. Laboratory tests revealed leukocytosis and anemia. A CT scan of the right hip revealed a moderately sized retroperitoneal hematoma. She was transferred to the intensive care unit, treated with supportive care, and was discharged two days later without any invasive intervention needed. Due to vague presentations, spontaneous retroperitoneal hemorrhages can be misdiagnosed as a number of abdominal or pelvic processes. While our patient presented with hip pain, other presentations include abdominal masses, back pain, or hypotension. Some patients may progress to hemodynamic instability, femoral neuropathy, or abdominal compartment syndrome requiring rapid intervention to prevent further morbidity. In patients with vague abdominal or pelvic complaints who have risk factors such as advanced age and the use of anticoagulation therapy, spontaneous retroperitoneal hemorrhage should be considered to allow for early diagnosis before severe complications arise.

Standard coagulation assays alone are not sufficient to exclude surgically relevant rivaroxaban plasma concentrations

Background

While mainly larger hospitals have introduced routine anti-Xa assays for rivaroxaban (RXA), these are not readily available to smaller hospitals often relying on routine coagulation tests such as prothrombin time (PT) and activated partial thromboplastin time (aPTT).

The aim of our study was to investigate the effect of RXA plasma concentration on the standard coagulation tests PT (Quick test and INR) and aPTT in a large group of real-life patients. We further assessed whether normal results of these standard coagulation assays are sufficient to exclude surgically relevant RXA plasma concentration, defined as > 50 mcg/l.

Methods

This retrospective study included all patients between 2012 and 2016 where anti-Xa (calibrated for RXA), PT (Quick test and INR), and/or aPTT were determined from the same sample. PT is expressed as Quick value (% of normal plasma pool). In total, 1027 measurements in 622 patients were eligible for analysis: 752 measurements of 505 patients for Quick/INR and 594 measurements of 417 patients for aPTT.

Results

A moderate correlation of PT/Quick (Pearson's correlation coefficient − 0.59; p < 0.001), INR (Pearson's correlation coefficient 0.5; p < 0.001), and aPTT (Pearson's correlation coefficient 0.53; p < 0.001) with RXA plasma concentration was observed. However, in 50% of all samples with a normal PT/Quick, in 25% of all samples with a normal INR and in 80% of all samples with a normal aPTT residual RXA plasma concentration was surgically relevant.

Conclusion

Although a moderate correlation of RXA plasma concentration with PT/Quick, INR, and aPTT was observed, standard coagulation assays are not sufficient to exclude surgically relevant RXA plasma concentrations.

International Normalized Ratio as a Screening Test for Assessment of Anticoagulant Activity for Patients Treated With Rivaroxaban or Apixaban: A Pilot Study

Introduction: In patients treated with direct oral anti activated factor X (anti-FXa) anticoagulants such as apixaban and rivaroxaban, there are several emergency and non-emergency conditions in which anticoagulation activity should be measured. The validity of the common global clotting tests, prothrombin time and international normalized ratio (PT/INR) for determination of blood levels of these drugs, has been widely investigated. As the anticoagulation activity evaluation “calibrated anti-FXa” of these drugs is relatively more expensive and less available, we aimed to build a prediction model for anticoagulation activity assessment based on INR values.

Methods and Findings: One hundred sixty samples from 80 hospitalized patients treated with apixaban or rivaroxaban were tested using PT/INR and Anti-FXa chromogenic assay. Two blood samples, trough and peak, were collected from each subject. Participants were randomly divided into two equal groups. One group (n = 40) was used to build the model, which was validated by the second group (n = 40). There was a strong correlation between anti-FXa concentrations and INR in rivaroxaban treated patients (r = 0.899, p < 0.001). Therefore, we were able to build a formula for rivaroxaban patient group which reliably represent the relationship between these two parameters. The correlation in apixaban treated patients was less predictive (r = 0.798, p < 0.001) and the formula suggested could not be validated.

Conclusions: In our study, we developed a formula that estimates the anticoagulant activity of rivaroxaban by obtaining INR values. Where anti-FXa assay is unavailable, our proposed formula may be considered as a screening test for rivaroxaban.

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

Background

Apixaban 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 presentation

We 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.

Conclusions

This case suggests that concurrent genetic polymorphisms can impair multiple apixaban elimination pathways and thus substantially increase its exposure.

MIDAS (Minimally Invasive Drilling And Styptic) protocol - A modified approach to treating patients under therapeutic anticoagulants

Patients with cardiac or allied medical conditions mandating long term oral anticoagulant therapy form a sizeable database in an implant practice today. The management of such patients during surgical and dental procedures has always been debatable. Literature has documented evidence that indicates towards stopping the anticoagulant for a finite period. However, discontinuing anticoagulants is not always possible, given the risks of greater significance than the edentulous state. In such patients a minimally invasive flapless approach is preferred, having the potential to reduce bleeding, surgical time and postoperative edema. The purpose of this case series is to show a possible modified approach for dental implant placement using a CAD-CAM stent guided flapless approach without stopping of therapeutic anticoagulant medication.

Evaluation of the Effect of Apixaban on INR in the Inpatient Population

Direct oral anticoagulants (DOACs), particularly direct factor Xa inhibitors, have been associated with prolongation of the prothrombin time and the international normalized ratio (INR). Although DOACs do not require monitoring, elevations in the INR have been reported in in vitro and observational studies. The literature surrounding the extent of elevation and the clinical significance is limited. The objective of this study was to quantify the degree of INR elevation in hospitalized patients receiving apixaban. This was a single-center, retrospective, observational analysis of adult patients who received at least 1 dose of apixaban during their hospital admission and had at least 1 INR sample collected prior to and following administration. The major end point of this study was to characterize the effect of apixaban on the INR by determining the percentage of patients with an INR higher than our laboratory defined normal (defined as INR > 1.1). Minor end point outcomes included the incidence of an INR increase >0.3 from baseline INR and additional patient-specific factors that may influence INR elevation. Seventy-nine patients were included in the analysis. On day 1 of therapy, the median (interquartile range, IQR) INR was 1.4 (1.3:1.6) with 84.5% of patients having an elevated INR. The median (IQR) INR increased to 1.5 (1.4:1.6) and 1.7 (1.5:1.9) on day 4 and day 7, respectively. Of patients whose INR increased by more than 0.3, the median (IQR) change in INR from baseline was 0.5 (0.4:0.6). Apixaban is associated with a notable increase in INR in hospitalized patients, although it is not clear the clinical impact of the increase. Although literature does not support monitoring INR as a marker of apixaban activity, it is important for clinicians to understand the association apixaban has on the INR to avoid inappropriate interpretation of routine coagulation assays.