Potential Effect of Substituting Estimated Glomerular Filtration Rate for Estimated Creatinine Clearance for Dosing of Direct Oral Anticoagulants

Central Nervous System Medications: Pharmacokinetic and Pharmacodynamic Considerations for Older Adults

Most drugs have not been evaluated in the older population. Recognizing physiological alterations associated with changes in drug disposition and with the ultimate effect, especially in central nervous system-acting drugs, is fundamental. While considering pharmacokinetics, it should be noted that the absorption of most drugs from the gastrointestinal tract does not change in advanced age. There are only few data about the effect of age on the transdermal absorption of medications such as fentanyl. Absorption from an intramuscular injection may be similar in older adults as in younger patients. The distribution of lipophilic drugs (such as diazepam) is increased owing to a relative increase in the percentage of body fat, causing drug accumulation and prolonged drug elimination following cessation. Phase I drug biotransformation is variably decreased in aging, impacting elimination, and hepatic drug clearance has been shown to decrease in older individuals by 10-40% for most drugs studied. Lower doses of phenothiazines, butyrophenones, atypical antipsychotics, antidepressants (citalopram, mirtazapine, and tricyclic antidepressants), and benzodiazepines (such as diazepam) achieve the same extent of exposure. For renally cleared drugs with no prior metabolism (such as gabapentin), the glomerular filtration rate appropriately estimates drug clearance. Important pharmacodynamic changes in older adults include an increased sedative effect of benzodiazepines at a given drug exposure, and a higher sensitivity to mu opiate receptor agonists and to opioid adverse effects. Artificial intelligence, physiologically based pharmacokinetic modeling and simulation, and concentration-effect modeling enabling a differentiation between the pharmacokinetic and the pharmacodynamic effects of aging might help to close some of the gaps in knowledge.

Impact of renal function variability on long-term prognosis in ischemic stroke patients with atrial fibrillation

Background

Although renal dysfunction is associated with adverse clinical outcomes in patients with atrial fibrillation (AF) following stroke, the impact of renal function variability is unclear.

Aim

This study aimed to assess the association between renal function variability and various adverse clinical outcomes in patients with transient ischemic attack (TIA)/ischemic stroke and atrial fibrillation (AF).

Methods

We conducted a population-based study and retrospectively identified patients hospitalized with a diagnosis of TIA/ischemic stroke and AF during 2016-2020 using the Clinical Data Analysis and Reporting System of Hong Kong. Serial serum creatinine tested upon the onset of TIA/ischemic stroke and during their subsequent follow-up was collected. Renal function variability was calculated using the coefficient of variation of the estimated glomerular filtration rate (eGFR). Clinical endpoints that occurred during the study period were captured and included ischemic stroke/systemic embolism, intracerebral hemorrhage (ICH), total bleeding, major adverse cardiovascular events (MACE), cardiovascular, non-cardiovascular, and all-cause mortality. Competing risk regression and Cox proportional hazard regression models were used to assess the associations of renal function variability with the outcomes of interest.

Results

A total of 3,809 patients (mean age 80 ± 10 years, 43% men) who satisfied the inclusion and exclusion criteria were followed up for a mean of 2.5 ± 1.5 years (9,523 patient-years). The mean eGFR was 66 ± 22 mL/min/1.73 m2 at baseline, and the median number of renal function tests per patient during the follow-up period was 20 (interquartile range 11-35). After accounting for potential confounders, a greater eGFR variability was associated with increased risks of recurrent ischemic stroke/systemic embolism [fully adjusted subdistribution hazard ratio 1.11, 95% confidence interval (CI) 1.03-1.20], ICH (1.17, 1.01-1.36), total bleeding (1.13, 1.06-1.21), MACE (1.22, 1.15-1.30), cardiovascular (1.49, 1.32-1.69), non-cardiovascular (1.43, 1.35-1.52), and all-cause mortality (fully adjusted hazard ratio 1.44, 1.39-1.50).

Conclusion

Visit-to-visit renal function variability is independently associated with adverse clinical outcomes in TIA/ischemic stroke patients with AF. Further large-scale studies are needed to validate our results.

Efficacy and Safety of Different Doses of Rivaroxaban and Risk Factors for Bleeding in Elderly Patients with Venous Thromboembolism: A Real-World, Multicenter, Observational, Cohort Study

INTRODUCTION

Venous thromboembolism (VTE) consists of deep vein thrombosis (DVT) and pulmonary embolism (PE). Rivaroxaban is a direct oral anticoagulant (DOAC) inhibiting activated coagulation factor X (FXa), and exerts several advantages in the treatment of VTE compared to conventional therapy. However, the efficacy and safety of rivaroxaban in elderly patients with VTE was still poorly understood.

METHODS

The study was carried out using an observational and non-interventional approach. A total of 576 patients aged ≥ 60 years with newly diagnosed VTE were included in the study. All patients received rivaroxaban with recommended treatment duration of ≥ 3 months for secondary prevention. In addition, 535 elderly patients with various diseases except VTE were included in the study in a retrospective and randomized way.

RESULTS

The total bleeding rate was 12.2% (70/576). Major bleeding and non-major clinically relevant (NMCR) bleeding occurred in 4 (0.69%) patients and 5 (0.87%) patients, respectively. The rate of recurrent VTE was 5.4%. The mean level of D-dimers was increased by 467.2% in the elderly patients with VTE compared with the elderly patients without VTE. The elderly patients with VTE receiving rivaroxaban at a dose of 10 mg once daily (n = 134) had lower risk for bleeding (3.7% vs 14.7%; P = 0.001) and a similar rate of recurrent VTE (4.5% vs 5.7%; P = 0.596) as compared to the elderly patients with VTE receiving rivaroxaban at higher doses including 15 mg once daily and 20 mg once daily (n = 442). In addition, age, concomitant aspirin, hemoglobin, activated partial thromboplastin time (APTT), and rivaroxaban doses were independent predictive factors for bleeding events.

CONCLUSIONS

The study suggested that a dose of 10 mg once daily should be the priority in elderly patients with VTE receiving long-term rivaroxaban anticoagulation therapy in view of reduced bleeding risk.

Kidney function estimators for drug dose adjustment of direct oral anticoagulants in older adults with atrial fibrillation

Background

The Cockcroft-Gault equation (CrClC-G) is recommended for dose adjustment of direct oral anticoagulant drugs (DOACs) to kidney function. We aimed to assess whether defining DOAC dose appropriateness according to various kidney function estimators changed the associations between dose appropriateness and adverse events in older adults with atrial fibrillation (AF).

Methods

Participants of the Berlin Initiative Study with AF and treated with DOACs were included. We investigated CrClC-G and estimated glomerular filtration rate (eGFR) using the Chronic Kidney Disease Epidemiology Collaboration and European Kidney Function Consortium equations based on creatinine and/or cystatin C. Marginal structural Cox models yielded confounder-adjusted hazard ratios for the risk of mortality, thromboembolism and bleeding associated with dose status.

Results

A total of 224 patients were included in the analysis (median age 87 years). Using CrClC-G, 154 (69%) had an appropriate dose of DOACs, 52 (23%) were underdosed and 18 (8%) were overdosed. During a 39-month median follow-up period, 109 (14.9/100 person-years) participants died, 25 (3.6/100 person-years) experienced thromboembolism and 60 (9.8/100 person-years) experienced bleeding. Dose status was not associated with mortality and thromboembolism, independent of the equation. Underdose status was associated with a lower risk of bleeding with all the equations compared with the appropriate dose group. In participants with discrepancies in dose status using CrClC-G and eGFR equations, the occurrence of endpoints did not differ between participants having an appropriate dose using CrClC-G or eGFR.

Conclusion

In older adults with AF, the association of DOAC dose status with adverse events did not differ when using CrClC-G or eGFR. Our results suggest that eGFR equations are not inferior to CrClC-G within this context.

Pharmacokinetics and pharmacodynamics of direct oral anticoagulants

INTRODUCTION

Direct oral anticoagulants (DOACs) have overtaken vitamin K antagonists to become the most widely used method of anticoagulation for most indications. Their stable and predictable pharmacokinetics combined with relatively simple dosing, and the absence of routine monitoring has made them an attractive proposition for healthcare providers. Despite the benefits of DOACs as a class, important differences exist between individual DOAC drugs in respect of their pharmacokinetic and pharmacodynamic profiles with implications for dosing and reversal in cases of major bleeding.

AREAS COVERED

This review summarizes the state of knowledge relating to the pharmacokinetics of dabigatran (factor IIa/thrombin inhibitor) and apixaban, edoxaban and rivaroxaban (factor Xa) inhibitors. We focus on pharmacokinetic differences between the drugs which may have clinically significant implications.

EXPERT OPINION

Patient-centered care necessitates a careful consideration of the pharmacokinetic and pharmacodynamic differences between DOACs, and how these relate to individual patient circumstances. Prescribers should be aware of the potential for pharmacokinetic drug interactions with DOACs which may influence prescribing decisions in patients with multiple comorbidities. In order to give an appropriate dose of DOAC drugs, accurate estimation of renal function using the Cockcroft-Gault formula using actual body weight is necessary. An increasing body of evidence supports the use of DOACs in patients who are obese, and this is becoming more routine in clinical practice.

DOAC Dosing Discordance Using Different Estimates of Kidney Function and Outcomes

Direct oral anticoagulants (DOACs) are indicated for the prevention of stroke in nonvalvular atrial fibrillation. Although Food and Drug Administration labeling for DOACs uses estimated creatinine clearance according to the Cockcroft-Gault (C-G) equation, estimated glomerular filtration rate according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is often reported. The objectives of this study were to evaluate DOAC dosing discordance and to determine whether discordance based on various estimates of kidney function is associated with bleeding or thromboembolism. The study was an institutional review board approved retrospective analysis of patients at UPMC Presbyterian Hospital from January 1, 2010, to December 12, 2016. Data were obtained through electronic medical records. Adults who received a medication charge for rivaroxaban or dabigatran, had a diagnosis code for atrial fibrillation, and had a serum creatinine within 3 days of DOAC initiation were included. Doses were considered discordant if the calculated dose based on CKD-EPI did not match the patient's dose during index admission, if dosed correctly using C-G. Association of discordance with dabigatran, rivaroxaban, and clinical outcomes was determined using odds ratios and 95% confidence intervals. Rivaroxaban discordance was present among 49 of the 644 (8%) patients who were dosed correctly with C-G. Dabigatran discordance was present among 17 of the 590 (3%) patients who were dosed correctly. Discordance with rivaroxaban was found to increase the risk of thromboembolism when using CKD-EPI (odds ratio, 2.83; 95% CI, 1.02-7.79, P = .045) versus C-G. Our findings emphasize the need to dose DOACs, specifically rivaroxaban, appropriately in patients with nonvalvular atrial fibrillation.

Challenges and Possible Solutions to Direct-Acting Oral Anticoagulants (DOACs) Dosing in Patients with Extreme Bodyweight and Renal Impairment

This article aims to highlight the dosing issues of direct oral anticoagulants (DOACs) in patients with renal impairment and/or obesity in an attempt to develop solutions employing advanced data-driven techniques. DOACs have become widely accepted by clinicians worldwide because of their superior clinical profiles, more predictable pharmacokinetics, and hence more convenient dosing relative to other anticoagulants. However, the optimal dosing of DOACs in extreme bodyweight  patients and patients with renal impairment is difficult to achieve using the conventional dosing approach. The standard dosing approach (fixed-dose) is based on limited data from clinical studies. The existing formulae (models) for determining the appropriate doses for these patient groups leads to suboptimal dosing. This problem of mis-dosing is worsened by the lack of standardized laboratory parameters for monitoring the exposure to DOACs in renal failure and extreme bodyweight patients. Model-informed precision dosing (MIPD) encompasses a range of techniques like machine learning and pharmacometrics modelling, which could uncover key variables and relationships as well as shed more light on the pharmacokinetics and pharmacodynamics of DOACs in patients with extreme bodyweight or renal impairment. Ultimately, this individualized approach-if implemented in clinical practice-could optimise dosing for the DOACs for better safety and efficacy.

Reclassification, Thromboembolic, and Major Bleeding Outcomes Using Different Estimates of Renal Function in Anticoagulated Patients With Atrial Fibrillation: Insights From the PREFER-in-AF and PREFER-in-AF Prolongation Registries

BACKGROUND

The Cockcroft-Gault formula is recommended to determine a renal indication for dose reduction of dabigatran, edoxaban, and rivaroxaban. Nephrology guidelines now recommend the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formulae as more accurate estimates of glomerular filtration rate.

METHODS

We analyzed anticoagulated patients with atrial fibrillation who were enrolled in the Prevention of Thromboembolic Events - European Registry in Atrial Fibrillation (PREFER in AF). The proportion of patients with dissimilar renal dosing indications was assessed when applying Cockcroft-Gault, MDRD, or CKD-EPI. Thromboembolic and major bleeding events at 1 year were compared in patients in whom Cockcroft-Gault and CKD-EPI provided concordant or discordant results around a threshold of 50 mL/minute.

RESULTS

Out of 1288 patients with atrial fibrillation with chronic kidney disease in whom Cockcroft-Gault suggested a dose reduction of dabigatran, edoxaban, or rivaroxaban (creatinine clearance ≤50 mL/minutes), 19% and 16% were reclassified to the respective higher doses, and 24% and 23% to the respective lower doses by applying the MDRD and CKD-EPI formulae, respectively. In patients potentially receiving a different dose of dabigatran, edoxaban, or rivaroxaban when using CKD-EPI, we observed an excess of thromboembolic events (4.1% versus 0.8%; odds ratio, 5.5 [95% CI, 1.5-20.8]; P=0.01). Major bleeding rates were nonsignificantly different in the discordance versus concordance group (5.7% versus 2.7%; odds ratio, 2.2 [95% CI, 0.9-5.6]; P=0.09).

CONCLUSIONS

The MDRD and CKD-EPI formulae suggest a different dosing in up to a quarter of anticoagulated patients with atrial fibrillation. This seems to impact hard outcomes.

Direct Oral Anticoagulants in the Treatment of Venous Thromboembolism: Use in Patients with Advanced Renal Impairment, Obesity, or Other Weight-Related Special Populations

There are currently more than 7 million patients taking a direct oral anticoagulant (DOAC), with more new prescriptions per year than warfarin. Despite impressive efficacy and safety data for the treatment of venous thromboembolism, patients with obesity or advanced renal impairment represented a small portion of the patients enrolled in the phase 3 clinical trials. Therefore, to evaluate the potential use of DOACs in these special populations, clinicians need to have an understanding of the pharmacokinetics and pharmacodynamics of these agents in these settings. Since data from randomized controlled trials are limited, data from observational trials are helpful in gaining comfort with the use of DOACs in these special populations. Selecting the appropriate dose for each agent is imperative in achieving optimal patient outcomes. We provide an extensive review of the pharmacokinetics, pharmacodynamics, phase 3 clinical trials, and observational studies on the use of DOACs in patients with advanced renal impairment, obesity, or other weight-related special populations to provide clinicians with a comprehensive understanding of the data for optimal drug and dose selection.

Relationship between the degree of renal dysfunction and the safety and efficacy outcomes in patients with atrial fibrillation receiving direct oral anticoagulants

BACKGROUND

The clinical evaluation of a direct oral anticoagulant (DOAC) treatment for atrial fibrillation (AF) patients with renal dysfunction has not been sufficiently studied. This study aimed to evaluate the safety and efficacy of DOACs for patients with a severely impaired renal function.

METHODS

This was a retrospective and observational study in a single center. We enrolled 894 consecutive AF patients who were prescribed DOACs, and divided them into three groups based on their creatinine clearance (CrCl) value: CrCl ≥ 50 mL/min group (n = 634), CrCl 30-49 mL/min group (n = 207), and CrCl 15-29 mL/min group (n = 53). We evaluated the occurrence of major bleeding (MB) as the safety outcome and thromboembolic events (TEs) as the efficacy outcome during the follow-up.

RESULTS

The incidence of MB in the CrCl 15-29 mL/min group was significantly higher than in the other groups (CrCl ≥ 50 mL/min group, 0.8/100 person-years; CrCl 30-49 mL/min group, 1.2/100 person-years; CrCl 15-29 mL/min group, 9.0/100 person-years, log rank test, P < .001). On the other hand, there was no significant difference in the incidence of TEs among the three groups. A multivariate analysis using a Cox proportional hazard model adjusted for the age revealed that the CrCl 15-29 mL/min group was significantly associated with increased MB compared to the CrCl ≥ 50 mL/min group (hazard ratio: 9.76, 95% confidence interval: 2.69-35.5, P < .001). Similar results were observed when adjusting for other multiple clinical factors.

CONCLUSION

This study demonstrated that the degree of renal dysfunction was a significant prognostic factor for MB in AF patients receiving DOACs.

Accuracy of freely available online GFR calculators using the CKD-EPI equation

Purpose

Estimated glomerular filtration rate (eGFR) as calculated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is used for detection of chronic kidney disease and drug dose adjustment. The purpose of the present study was to investigate the accuracy of freely available eGFR online calculators.

Methods

All identified CKD-EPI online calculators were run with five reference cases differing in age, sex, serum creatinine, and ethnicity. Conversion from eGFR_indexed (unit ml/min per 1.73 m²) to eGFR_non-indexed (unit ml/min) and creatinine unit from milligramme/decilitre to micromole/litre was checked, if available.

Results

Only 36 of 47 calculators (76.6%) produced accurate eGFR results for all reference cases. Eight of 47 (17.0%) calculators were considered as faulty because of errors relating to ethnicity (4 calculators), to conversion of the eGFR unit (2 calculators), to erroneous eGFR values without obvious explanation (2 calculators), to conversion of the creatinine unit (1 calculator), and to an error in the eGFR unit displayed (1 calculator). Overall, 28 errors were found (range 59 to 147% of the correct eGFR value), the majority concerning calculation of eGFR_indexed and the conversion to eGFR_non-indexed. Only 7 of 47 (14.9%) calculators offered conversion of the eGFR unit.

Conclusions

Erroneous calculations that might lead to inappropriate clinical decision-making were found in 8 of 47 calculators. Thus, online calculators should be evaluated more thoroughly after implementation. Conversion of eGFR units that might be needed for drug dose adjustments should be implemented more often.

Electronic supplementary material

The online version of this article (10.1007/s00228-020-02932-x) contains supplementary material, which is available to authorized users.

Should We Continue Assessing Glomerular Filtration Rate with the Cockroft-Gault Formula in NOAC-Treated Patients? The Magnitude of the Problem

Despite the proven superiority of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) over the Cockcroft–Gault (CG) formula, current guidelines recommend the latter to assess renal function in patients treated with non-vitamin K antagonist oral anticoagulants (NOACs). To assess the relationship between the CG and the recommended CKD-EPI formulas, in a cohort of atrial fibrillation (AF) patients treated with NOACs, and the misclassifications introduced by the CG formula for renal function levels, we estimated renal function with three equations: CG, CKD-EPI with body surface adjustment (1.73 mL/m², CKD-EPI) and without such adjustment (CKD-EPI_noBSA), in all consecutive AF patients discharged from NOACs from the Cardiology Division of a main city hospital between February 1st and May 31st 2018. We compared the different estimates of glomerular filtration rate and potential renal function class misclassifications. We reclassified 37/115 patients (32.1%) when switching from the CG to the CKD-EPI; and 24/115 (20.8%) switching from the CG to the CKD-EPI_noBSA formulas. Class reallocation was distributed across all levels of renal function, but mostly affected the “hyper-normal” function. In estimating consequences of such reallocation, a change in NOAC dosages would have occurred in 10/115 patients (8.7%) when switching from the CG to the CKD-EPI formula and in 10/115 patients when switching from the CG to the CKD-EPI_noBSA formula. Although the CG method has been traditionally used to calculate renal function in all NOAC studies, a renal dysfunction class reallocation occurs in a substantial fraction of hospital-admitted AF patients with the use of better estimates of renal function.

Impact of direct oral anticoagulant off-label doses on clinical outcomes of atrial fibrillation patients: A systematic review

AIMS

Worldwide observational studies are evidencing discordance between guidelines and real-world practice regarding direct oral anticoagulant drug (DOAC) doses. This systematic review summarizes and evaluate DOACs use in real-world practice.

METHODS

This review was performed following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines searching PubMed (MEDLINE) and Medscape databases.

RESULTS

Data from 75 studies showed that most of the patients treated with DOACs for stroke prevention in atrial fibrillation received doses in accordance to the guidelines. However, a significant number of patients received off-label doses (25-50% in most of the studies evaluated). DOAC overdosing was associated with increased all-cause mortality and worse bleeding events while underdosing was associated with increased cardiovascular hospitalization and, particularly for apixaban, with a nearly 5-fold increased risk of stroke.

CONCLUSION

Patients prescribed with off-label DOAC doses did not receive the full benefit of anticoagulation and presented an increased risk of stroke, bleeding and/or adverse effects.

Characteristics and outcomes in patients with atrial fibrillation receiving direct oral anticoagulants in off-label doses

Background

We evaluated adherence to dosing criteria for patients with atrial fibrillation (AF) taking dabigatran or rivaroxaban and the impact of off-label dosing on thromboembolic and bleeding risk.

Methods

We used data for a retrospective cohort from a large U.S. health plan for Medicare beneficiaries age > =65 years with AF who initiated dabigatran or rivaroxaban during 2010–2016. Stroke and major bleeding were quantified in patients who were eligible for low dose but received standard dose, and in patients who were eligible for standard dose but received low dose.

Results

We identified 8035 and 19,712 patients who initiated dabigatran or rivaroxaban, respectively. Overall, 1401 (17.4%) and 7820 (39.7%) patients who received dabigatran and rivaroxaban met criteria for low dose, respectively. Of those, 959 (68.5%) and 3904 (49.9%) received standard dose. In contrast, 1013 (15.3%) and 2551 (21.5%) of patients eligible for standard dose dabigatran and rivaroxaban received low dose. Mean follow-up for patients eligible for low and standard dose dabigatran and rivaroxaban were 13.9, 15.1, 10.1, and 12.3 months, respectively. In unadjusted analyses, patients eligible for low or standard dose dabigatran and rivaroxaban but receiving off-label dose, had no differences in the rates of ischemic stroke. Among patients who met criteria for standard dose direct oral anticoagulants (DOAC), use of low dose was associated with significantly higher risk of any major bleeding (Dabigatran: HR = 1.44; 95% CI 1.14–1.8, P = 0.002, Rivaroxaban HR 1.34, 95% CI 1.11–1.6, P = 0.002) and gastrointestinal bleeding (Dabigatran: HR = 1.48; 95% CI 1.08–2, P = 0.016). In patients who met criteria for low dose DOACs, there was lower risk of major bleeding (Dabigatran: HR = 0.59; 95% CI 0.43–0.8, P < 0.001), gastrointestinal (Rivaroxaban: HR 0.79; 95% CI 0.64–0.98, P = 0.03) and intracranial bleeding (Dabigatran: HR = 0.33; 95% CI 0.12–0.9, P = 0.001) with standard dosing. After propensity matching, use of off-label doses was not associated with stroke, major, gastrointestinal or intracranial bleeding for either dabigatran or rivaroxaban.

Conclusions

While a significant number of patients receive higher or lower dose of dabigatran and rivaroxaban than recommended, we found no evidence of significant impact on thromboembolic or hemorrhagic outcomes.

Role of direct oral anticoagulants in patients with kidney disease

The anticoagulation field is experiencing a renaissance that began with regulatory approval of the direct thrombin inhibitor dabigatran, a direct oral anticoagulant (DOAC), in 2010. The DOAC medication class has rapidly evolved to include the additional approval of 4 direct factor Xa inhibitors. Commensurately, DOAC use has increased and collectively account for the majority of new anticoagulant prescriptions. Despite exclusion of patients with moderate-to-severe kidney disease from most pivotal DOAC trials, DOACs are increasingly used in this setting. An advantage of DOACs is similar or improved antithrombotic efficacy with less bleeding risk when compared with traditional agents. Several post hoc analyses, retrospective studies, claims data studies, and meta-analyses suggest that these benefits extend to patients with kidney disease. However, the lack of randomized controlled trial data in specific kidney disease settings, with their unique pathophysiology, should be a call to action for the kidney community to systematically study these agents, especially because early data suggest that DOACs may pose less risk of anticoagulant-related nephropathy than do vitamin K antagonists. Most DOACs are renally cleared and are significantly protein bound in circulation; thus, the pharmacokinetics of these drugs are influenced by reduced renal function and proteinuria. DOACs are susceptible to altered metabolism by P-glycoprotein inhibitors and inducers, including drugs commonly used for the management of kidney disease comorbidities. We summarize the currently available literature on DOAC use in kidney disease and illustrate knowledge gaps that represent important opportunities for prospective investigation.

Safety of Using Direct Oral Anticoagulants in Patients with Atrial Fibrillation and Chronic Kidney Disease

The purpose of this review is to examine the possibilities and prospects for the use of direct oral anticoagulants for the prevention of thromboembolic complications in patients with atrial fibrillation and chronic kidney disease. Chronic kidney disease is an independent risk factor for cardiovascular complications. Atrial fibrillation is associated with a higher risk of developing chronic kidney disease and more rapid progression of existing renal pathology. The presence of chronic kidney disease in atrial fibrillation on the one hand leads to an increased risk of thromboembolism, and on the other to an increased risk of bleeding when using anticoagulants. The standard for the prevention of thromboembolic complications in atrial fibrillation, including those with concomitant renal pathology, was considered warfarin for many years. However, modern studies have shown that the use of warfarin may enhance vascular calcification in patients with chronic kidney disease, which in turn may lead to an increased risk of ischemic strokes.

Analyzing clinical recommendations, randomized studies, meta-analyzes and a systematic review on the use of anticoagulants in patients with atrial fibrillation and renal pathology, revealed the advantage of using direct oral anticoagulants over warfarin at stage 1-3 of chronic kidney disease. Data on the use of direct oral anticoagulants with a more pronounced renal dysfunction and in patients on dialysis is limited due to the lack of a sufficient number of large randomized studies. Due to the presence of renal clearance in all oral anticoagulants, their pharmacokinetics changes to some extent with a decrease in the glomerular filtration rate, which requires dose adjustment of drugs depending on creatinine clearance. Therefore, the use of anticoagulants for the prevention of thromboembolic complications during atrial fibrillation requires special attention in patients with chronic kidney disease.

The use of direct oral anticoagulants in chronic kidney disease

Increasing use of direct oral anticoagulants (DOACs) has made management of non-valvular atrial fibrillation and venous thromboembolism easier in most patients. But the presence of co-existing renal impairment could render the use of DOACs problematic because all of these drugs have varying degrees of renal excretion. In this paper we address misconceptions about the safety and efficacy of DOACs in moderate-severe renal impairment by presenting a summary of the literature from phase III trials and real-world studies. It also addresses the important consideration of correct estimate of renal function for DOAC dosing. It is hoped that the review will serve as a valuable resource for clinicians involved in anticoagulation decision-making in patients with renal impairment to guide the choice of most suitable agent. Accurate dosing is of particular relevance as registry data suggests it is done inconsistently and may be resulting in avoidable thromboembolic and bleeding events.

Oral Anticoagulation in Chronic Kidney Disease and Atrial Fibrillation

BACKGROUND

Cardiological societies recommend, in their guidelines, that patients with atrial fibrillation and an intermediate (or higher) risk of stroke and systemic embolization should be treated with oral anticoagulant drugs. For patients who do not have mitral valve stenosis or a mechanical valve prosthesis, non-vitamin-K dependent oral anticoagulants (NOAC) are preferred over vitamin K antagonists (VKA) for this purpose. It is unclear, however, whether patients with chronic kidney disease and atrial fibrillation benefit from oral anticoagulation to the same extent as those with normal kidney function. It is also unclear which of the two types of anti - coagulant drug is preferable for patients with chronic kidney disease; NOAC are, in part, renally eliminated.

METHODS

This review is based on pertinent publications retrieved by a selective literature search, and on international guidelines.

RESULTS

Current evidence suggests that patients with atrial fibrillation who have chronic kidney disease with a glomerular filtration rate (GFR) above 15 mL/ min/1.73 m² should be treated with an oral anticoagulant drug if they have an at least intermediate risk of embolization, as assessed with the CHA2DS2-VASc score. For patients with advanced chronic kidney disease (GFR from 15 to 29 mL/ min/1.73 m²), however, this recommendation is based only on registry studies. For dialysis patients with atrial fibrillation, decisions whether to give oral anticoagulant drugs should be taken on an individual basis, in view of the elevated risk of hemorrhage and the unclear efficacy of such drugs in these patients. The subgroup analyses of the NOAC approval studies show that, for patients with atrial fibrillation and chronic kidney disease with a creatinine clearance of >25-30 mL/min, NOAC should be given in preference to VKA, as long as the patient does not have mitral valve stenosis or a mechanical valve prosthesis. For those whose creatinine clearance is less than 25 mL/min, the relative merits of NOAC versus VKA are still debated.

CONCLUSION

The cardiological societies' recommendation that patients with atrial fibrillation should be given oral anticoagulant drugs applies to the majority of such patients who also have chronic kidney disease.

Medication burden attributable to chronic co-morbid conditions in the very old and vulnerable

OBJECTIVE

Polypharmacy is common in older patients but relationships between polypharmacy and common co-morbid conditions have not been elucidated. Our goal was to determine relationships between daily oral medication use and common co-morbid disease dyads and triads using comprehensive medication and diagnostic data from a national sample of nursing homes (NH).

DESIGN

Retrospective, cross-sectional study.

SETTING

Nationally representative sample of U.S. Nursing Homes.

PARTICIPANTS

Nationally representative sample of long-term stay residents (n = 11734, 75% women) aged 65 years or older.

MEASUREMENTS

Diagnosis and medication data were analyzed. Proportion of daily oral medication intake attributed to treatment of common two-(dyads) and three-disease (triad) combinations and "health maintenance" agents (vitamins, dietary supplements, stool softeners without related diagnoses) was determined.

RESULTS

Older NH residents received slightly >8 oral medications/day with the number related to number of medical diagnoses (p < .0001). One third of chronic oral medication intake/day (excluding health maintenance agents) could be attributed to dyad combinations and about half to triad combinations despite an average of 5 other diagnoses. Triads were comprised of hypertension +/- arthritis +/- vascular disease, +/-depression, +/- osteoporosis +/- gastroesophageal reflux disease and +/- diabetes. Health maintenance agents accounted for 15-17% of daily oral medication intake (1.4 medications) such that almost two-thirds of daily oral medications were attributable to disease triads plus health maintenance. Fewer medications were prescribed for NH residents over age 85 (decreased ACE inhibitor and HMG CoA reductase inhibitor USE (p < .001)) while use of Alzheimer medications was higher (p < .01).

CONCLUSIONS

A large fraction of daily oral medications were attributed to management of common co-morbid disease dyads and triads. Efforts to reduce polypharmacy and unwanted medication interactions could focus on regimens for common co-morbid dyads and triads in varying populations.

Establishing the presence or absence of chronic kidney disease: Uses and limitations of formulas estimating the glomerular filtration rate

The development of formulas estimating glomerular filtration rate (eGFR) from serum creatinine and cystatin C and accounting for certain variables affecting the production rate of these biomarkers, including ethnicity, gender and age, has led to the current scheme of diagnosing and staging chronic kidney disease (CKD), which is based on eGFR values and albuminuria. This scheme has been applied extensively in various populations and has led to the current estimates of prevalence of CKD. In addition, this scheme is applied in clinical studies evaluating the risks of CKD and the efficacy of various interventions directed towards improving its course. Disagreements between creatinine-based and cystatin-based eGFR values and between eGFR values and measured GFR have been reported in various cohorts. These disagreements are the consequence of variations in the rate of production and in factors, other than GFR, affecting the rate of removal of creatinine and cystatin C. The disagreements create limitations for all eGFR formulas developed so far. The main limitations are low sensitivity in detecting early CKD in several subjects, e.g., those with hyperfiltration, and poor prediction of the course of CKD. Research efforts in CKD are currently directed towards identification of biomarkers that are better indices of GFR than the current biomarkers and, particularly, biomarkers of early renal tissue injury.

Renal Function Considerations for Stroke Prevention in Atrial Fibrillation

Renal impairment increases risk of stroke and systemic embolic events and bleeding in patients with atrial fibrillation. Direct oral anticoagulants (DOACs) have varied dependence on renal elimination, magnifying the importance of appropriate patient selection, dosing, and periodic kidney function monitoring. In randomized controlled trials of nonvalvular atrial fibrillation, DOACs were at least as effective and associated with less bleeding compared with warfarin. Each direct oral anticoagulant was associated with reduced risk of stroke and systemic embolic events and major bleeding compared with warfarin in nonvalvular atrial fibrillation patients with mild or moderate renal impairment. Renal function decrease appears less impacted by DOACs, which are associated with a better risk-benefit profile than warfarin in patients with decreasing renal function over time. Limited data address the risk-benefit profile of DOACs in patients with severe impairment or on dialysis.

Incomplete Resolution of Deep Vein Thromboses during Rivaroxaban Therapy

We present the case of a patient with a deep vein thrombosis (DVT) who failed rivaroxaban therapy. Our patient initially presented with left lower extremity edema, erythema, and pain. He was subsequently started on rivaroxaban therapy for a combined treatment period of 12 months, during and after which he persisted to have evidence of a DVT. The patient's prescribed drug regimen was changed from rivaroxaban to warfarin, which demonstrated a rapid resolution of the DVTs as determined by ultrasound assessment of our patient's lower extremity veins. Rivaroxaban, a factor Xa inhibitor, is a well-known oral anticoagulant that is used for a variety of indications and has become a mainstay in the treatment of deep vein thrombosis. With the introduction and emergence of this medication in the clinic, postmarketing reports of efficacy or lack thereof are important to review. In conclusion, we anticipate that it is likely that there are other patients with DVTs who may not respond to rivaroxaban and for whom alternative anticoagulation therapies should be explored.

Nonvitamin K-dependent oral anticoagulants (NOACs) in chronic kidney disease patients with atrial fibrillation

Atrial fibrillation (AF) represents the most common arrhythmia in patients with chronic kidney disease (CKD). As in the general population, in CKD patients AF is associated with an increased risk of thromboembolism and stroke. However, CKD patients, especially those on renal replacement therapy (RRT), also exhibit an increased risk of bleeding, especially from the gastrointestinal tract. Oral anticoagulation is the most effective form of thromboprophylaxis in patients with AF presenting increased risk of stroke. Limited evidence on efficacy, the increased risk of bleeding as well as some concern regarding the use of warfarin in CKD, has often resulted in the underuse of anticoagulation CKD patients. A large body of evidence suggests that non-vitamin K-dependent oral anticoagulant agents (NOACs) significantly reduce the risk of stroke, intracranial hemorrhage, and mortality, with lower to similar major bleeding rates compared with vitamin K antagonist such as warfarin in normal renal function subjects. Hence, they are currently recommended for patients with atrial fibrillation at risk for stroke. However, NOACs metabolism is largely dependent on the kidneys for elimination and little is known in patients with creatinine clearance <25ml/min who were excluded from all pivotal phase 3 NOACs trials. This review focuses on the current pharmacokinetic, observational, and prospective data on NOACs in patients with moderate to advanced chronic kidney disease (creatinine clearance 15-49ml/min) and those on dialysis.