Practical issues with vitamin K antagonists: elevated INRs, low time-in-therapeutic range, and warfarin failure

Pulmonary Embolism and Right Ventricular Dysfunction: Mechanism and Management

Pulmonary embolism (PE) occurs when thrombi from deep vein thrombosis dislodge and obstruct pulmonary arteries, raising pulmonary artery pressure and straining the right ventricle. This strain can lead to right ventricular dysfunction (RVD), characterized by reduced cardiac output, impaired contractility, and potential development of chronic thromboembolic pulmonary hypertension. Clinically, PE may present with symptoms such as dyspnea, pleuritic chest pain, and tachycardia. Diagnosis is typically confirmed through computed tomography pulmonary angiography, biomarkers like D-dimer and cardiac troponins, and clinical scoring systems. Acute management focuses on hemodynamic support, including intravenous fluids and vasopressors, and may involve anticoagulation with low-molecular-weight heparin or direct oral anticoagulants. Severe cases may require systemic anticoagulation, catheter-directed techniques, and surgeries like pulmonary endarterectomy. Long-term management involves continued anticoagulation tailored to individual risk factors, with ongoing monitoring to prevent recurrence. Effective early diagnosis and management are crucial, as severe PE can significantly increase mortality and lead to serious complications. This review explores the pathophysiology, diagnosis, and management of PE and RVD.

Pharmacokinetic Interactions Between Abiraterone, Apalutamide, Darolutamide or Enzalutamide and Antithrombotic Drugs: Prediction of Clinical Events and Review of Pharmacological Information

PURPOSE

Abiraterone, apalutamide, darolutamide and enzalutamide are second-generation hormone therapies used for advanced prostate cancer; the majority of patients receiving these treatments are elderly, poly-medicated patients. Since their first market authorizations, their pharmacokinetic (PK) characteristics are increasingly well known. A potential risk of drug-drug interaction (DDI), especially with cardiovascular drugs, needs to be considered. In the case of antithrombotics, treatment imbalance can lead to severe consequences.

OBJECTIVES

To describe PK profiles of hormone therapies and antithrombotics and to predict DDIs and potentially related clinical events.

METHODS

PK profiles (CYP450 and P-gp substrate, inducer or inhibitor) are described by cross-referencing data sources (summary of product characteristics, European public assessment reports, PubMed database, Micromedex®, etc.); a description of the potential interactions with anti-cancer drugs for each DDI and related clinical events is provided. We discuss management recommendations, including those set out in international guidelines.

RESULTS

Antithrombotics are mainly metabolized by CYP 2C9, 2C19 or 3A4. For abiraterone (CYP 2C8, 2D6 inhibitor) and darolutamide (CYP 3A4 inducer), no interaction was identified with antithrombotics. For apalutamide (CYP 2C9, 2C19, 3A4 and P-gp inducer) and enzalutamide (CYP 2C9, 2C19, 3A4 inducer and P-gp inhibitor), several PK interactions were identified with antithrombotics, which could lead to various clinical events (haemorrhage or thromboembolism).

CONCLUSION

Numerous interactions are expected between enzalutamide or apalutamide and antithrombotics, for which management should be deployed on a case-by-case basis. PK and pharmaco-epidemiological studies could shed light on whether or not there are clinically significant events related to DDIs with antithrombotics.

Association of Different Anticoagulation Strategies With Outcomes in Patients Hospitalized With Acute Pulmonary Embolism

Background Therapeutic anticoagulation is the cornerstone of treatment for pulmonary embolism (PE), but the impact of different anticoagulation strategies on patient outcomes remains unclear. In this study, we assessed the association of different anticoagulation strategies with the outcomes of patients with acute PE. Methods A retrospective chart review of 207 patients with acute PE who were admitted to one of three urban teaching hospitals in the Mount Sinai Health System (in New York City) from January 2020 to September 2022 was performed. Demographic, clinical, and radiographic data were recorded for all patients. Multivariate regression analyses were performed to assess the association of different outcomes with the approach of therapeutic anticoagulation used. Results The median age of the included patients was 65 years, and 50.2% were women. The most common approach (n = 153, 73.9%) to therapeutic anticoagulation was initial treatment with unfractionated or low molecular weight heparin followed by a direct-acting oral anticoagulant (DOAC), while heparin alone (either unfractionated or low molecular weight heparin) was used in 37 (17.9%) patients, and another 17 (8.2%) patients were treated with heparin followed by bridging to warfarin. Hospital length of stay was longer for patients in the "heparin to warfarin" group (risk-adjusted incidence rate ratio of 2.52). The rates of in-hospital bleeding, all-cause 30-day mortality, and all-cause 30-day re-admissions did not have any significant association with the therapeutic anticoagulation approach used. Conclusion Patients with acute PE who were initially treated with heparin and subsequently bridged to warfarin had a longer hospital stay. Rates of in-hospital bleeding, 30-day mortality, and 30-day re-admission were not associated with the strategy of therapeutic anticoagulation employed.

Percutaneous Left Atrial Appendage Closure Among Patients With Diabetes (Insights from a National Database)

Atrial fibrillation is a major risk factor for stroke. Left atrial appendage closure (LAAC) has emerged as an alternative to anticoagulation for patients with high risk of bleeding. Diabetes mellitus (DM) is associated with adverse events after cardiac procedures. We sought to compare procedural and hospital outcomes in patients who underwent LAAC with and without DM. The Nationwide Inpatient Database was queried for patients with atrial fibrillation who underwent LAAC between January 1, 2016, and December 31, 2019. The primary outcome was all adverse events that included in-hospital death, acute myocardial infarction, cardiac arrest, stroke, pericardial effusion, pericardial tamponade, pericardiocentesis, pericardial window, and postprocedural hemorrhage requiring blood transfusion. Analysis included 62,220 patients who underwent LAAC from 2016 to 2019; 34.9% of patients had DM. There was a slight increase in the percentage of patients who underwent LAAC who had DM during the study period, from 29.92% to 34.93%. In unadjusted and adjusted analysis, there was no significant difference in all adverse events between patients with and without DM who underwent LAAC (9.18% vs 8.77%, respectively, adjusted p = 0.63), and no difference in length of stay. Patients with DM have higher risk of acute kidney injury (3.75 vs 1.96%, p <0.001). This nationwide retrospective study demonstrates that DM is not associated with an increase in adverse event rates in patients who underwent LAAC.

Rosendaal linear interpolation method appraising of time in therapeutic range in patients with 12-week follow-up interval after mechanical heart valve replacement

Background

The objective of this study was to evaluate the quality of anticoagulation by the time in therapeutic range (TTR) for patients with 12-week INR follow-up interval.

Materials and methods

From January 2018 to December 2020, a selective group of patients who underwent mechanical valve replacement and followed up at our anticoagulation clinic for adjustment of warfarin dose were enrolled. The incidences of complications of anticoagulation therapy were reported by linearized rates. TTR was calculated by the Rosendaal linear interpolation method.

Results

Two hundred and seventy-four patients were eligible for this study. The mean age of these patients was 52.8 ± 12.7 years, and 65.7% (180 cases) of them were females. The mean duration of warfarin therapy was 16.7 ± 28.1 months. A total of 1309 INR values were collected, representing 66789 patient days. In this study, the mean TTR was 63.7% ± 18.6%, weekly doses of warfarin were 20.6 ± 6.0 mg/weekly, and the mean monitoring interval for the patient was 53.6 ± 27.1 days. There were 153 cases in good TTR group (TTR ≥ 60%) and 121 cases in poor TTR group (TTR < 60%). The calculated mean TTR in both groups was 42.6% ± 22.1% and 74.8% ± 10.4%, respectively. Compared with the TTR ≥ 60% group, the TTR < 60% group exhibited a more prevalence of female gender (p = 0.001), atrial fibrillation (p < 0.001), NYHA ≥ III (p < 0.001), and lower preoperative left ventricular ejection fraction (LVEF, p = 0.032). In multivariate analysis, female gender (p = 0.023) and atrial fibrillation (p = 0.011) were associated with TTR < 60%. The incidence of major bleeding and thromboembolic events was 2.7% and 1.1% patient-years, respectively. There was one death which resulted from cerebral hemorrhage. The incidence of death was 0.5% patient-years. The difference in anticoagulation-related complications between the TTR < 60% group and the TTR ≥ 60% group was not statistically significant.

Conclusion

For patients with stable international normalized ratio monitoring results who are follow-up at anticoagulation clinics, a 12-week monitoring interval has an acceptable quality of anticoagulation. The female gender and atrial fibrillation were associated with TTR < 60%.

A retrospective study of real-world effectiveness and safety of rivaroxaban in patients with non-valvular atrial fibrillation and venous thromboembolism in Saudi Arabia

Background

Real-world evidence on factor Xa inhibitor (rivaroxaban) prescribing patterns, safety, and efficacy in patients with non-valvular atrial fibrillation (NVAF) and venous thromboembolism (VTE) is rare. Herein, we sought to examine the above outcomes in the largest academic center in the Kingdom of Saudi Arabia (KSA).

Methods

This is a retrospective observational study designed to examine the prescribing pattern, safety and real-world effectiveness of the factor Xa inhibitor rivaroxaban in patients with NVAF and VTE. Data on rivaroxaban prescriptions were collected and analyzed. Bleeding outcomes were defined as per the International Society on Thrombosis and Hemostasis (ISTH) definition.

Results

A total of 2,316 patients taking rivaroxaban recruited through several departments of King Saud University Medical City (KSUMC). The mean age was 61 years (±17.8) with 55% above the age of 60 and 58% were females. Deep vein thrombosis and pulmonary embolism (VTE) was the most prevalent reason for prescribing rivaroxaban, followed by NVAF. A total daily dosage of 15 mg was given to 23% of the patients. The incidence rate of recurrent thrombosis and recurrent stroke was 0.2%. Furthermore, rivaroxaban had a 0.04 percent incidence rate of myocardial infarction. Half of the patients with recurrent thrombosis and stroke were taking 15 mg per day. The incidence rate of major bleeding was 1.1%. More over half of the patients who experienced significant bleeding were taking rivaroxaban at a dosage of 20 mg per day. According to the HAS-BLED Score (>2 score), 48 percent of patients who experienced significant bleeding had a high risk of bleeding. Non-major bleeding occurred in 0.6% of cases. Similarly, 40% of patients with non-major bleeding were taking rivaroxaban at a dosage of 20 mg per day. According to the HAS-BLED Score, just 6.6% of these individuals had a high risk of bleeding. 93.4% of the patients, on the other hand, were at intermediate risk.

Conclusion

The prescription of rivaroxaban in this real-life cohort study differs from the prescribing label and the outcomes of a phase 3 randomised clinical trial. However, for individuals with VTE and NVAF, the 20 mg dose looked to be more efficacious than the pivotal trial outcomes. Furthermore, among patients with VTE and NVAF, rivaroxaban was linked to a decreased incidence of safety events such as recurrent thrombosis, recurrent stroke, MI, major bleeding, and non-major haemorrhage in a real-world environment.

The Connubium among diabetes, chronic kidney disease and atrial fibrillation

The burden of cardiovascular comorbid conditions was significantly higher in patients with Atrial Fibrillation (AF); most of them are affected by hypertension, Chronic Kidney Disease (CKD) and/or Diabetes Mellitus (DM). DM represents a well-known risk factor for the development and maintenance of AF; the coexistence of DM and AF is also associated with an increased risk of mortality and stroke. Moreover, DM is currently the main cause of renal impairment and the leading cause of dialysis in the world. The hyperglycemia is responsible for inducing redox imbalance and both systemic and intrarenal inflammation, playing a critical role in the pathogenesis of diabetic kidney disease. Long-term thromboembolic preventive therapy in AF patients with DM and CKD may be more challenging because both DM and CKD have been independently associated with an increased thromboembolic and bleeding risk, which results from the prothrombotic and pro-inflammatory status. Vitamin K Antagonists (VKAs) are characterized by numerous critical issues such as a narrow therapeutic window, increased tissue calcification and an unfavourable risk/benefit ratio with low stroke prevention effect and augmented risk of major bleeding. On the other hand, Direct Oral Anticoagulants (DOACs) are currently contraindicated in dialysis patients even if mounting evidence suggests that they may have a nephroprotective role in AF patients with DM and CKD. Consequently, the choice of anticoagulant therapy in this setting of patient seems to be very challenging. The aim of this review is to investigate the role of DOACs in diabetic patients and its nephroprotective role by reviewing the current literature.

[Comparative study in primary care of the stability of INR in patients treated with warfarin or fluindione for atrial fibrillation. The FLOWER study (FLuindione Or WarfarinE - Result INR)]

INTRODUCTION

The aim of our study was to compare the time spent within the target INR or Time in Therapeutic Range (TTR) of patients treated with fluindione to that of patients treated with warfarin for non-valvular atrial fibrillation (NVAF) and followed in general practice, with the hypothesis of a better TTR with warfarin, which is the VKA most commonly prescribed in France.

METHOD

Liberal nurses and general practitioners working in the Auvergne region recruited patients treated with fluindione or warfarin for NVAF. Patients' INRs (International Normalized Ratios) were recorded by medical analysis laboratories for 6 months. The primary endpoint was TTR, the secondary endpoint the number of hemorrhagic and/or thromboembolic events.

RESULTS

Of the 342 participants with a mean age of 75.3 ± 9.8 years, 239 (70%) were treated with fluindione and 103 (30%) with warfarin. The mean number of INRs achieved per patient was 9.2 ± 4.0 in the fluindione group and 9.3 ± 4.0 in the warfarin group (p=0.73). The median TTR of fluindione was 81.9% [63.5; 94.1] and that of warfarin was 81.3% [65.6; 92.6] (p=0.98). Twenty-eight of 263 patients reported hemorrhage (10.6%) and 4 reported thromboembolic events (0.8%), with no significant difference between the groups.

CONCLUSION

The TTRs of patients treated for NVAF with fluindione versus warfarin do not differ significantly over an observation period of 6 consecutive months in a patient population comparable to that of the publications in this field. However, these TTRs are significantly higher than those reported in the literature, with no difference between the two treatments. The TTRs of patients treated for VANF with fluindione versus warfarin do not differ significantly over a 6-month observation period in a patient population comparable to that of the publications in this indication.

Appropriateness of Prescribing Rivaroxaban at King Khalid University Hospital Riyadh

Background and aim

Warfarin is recognized as a first-line treatment for different coagulopathy conditions; however, guidelines also encourage the use of rivaroxaban as an alternative option. The recent approval of the novel oral anticoagulants (NOACs) has led to swift changes in anticoagulant prescribing practices. This study aimed to review rivaroxaban prescribing patterns in adult patients in a large tertiary care setting in the Kingdom of Saudi Arabia (KSA).

Materials and methods

A retrospective cross-sectional study was conducted from January 2019 to September 2020 at King Khalid University Hospital, Riyadh, KSA. Data was collected from the patient's medical record. Data analysis was performed with the Statistical Package for the Social Sciences (SPSS) IBM Corp. Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp.

Results

A total of 309 patients were included in this study. Rivaroxaban use for non-valvular atrial fibrillation (NVAF) was relatively higher than deep venous thrombosis/pulmonary embolism (DVT/PE). 45% of the patients had NVAF, followed by DVT/PE (26%), and DVT/PE prophylaxis (25%). Fifty-six patients, (18%) received an inappropriate dose of rivaroxaban for NVAF.

Conclusion

This study found a relatively high percentage of inappropriate rivaroxaban prescribing, predominantly because of inappropriate dosing, which can potentially increase medication-related events. The use of rivaroxaban should be monitored to increase the appropriateness of therapy and improve patient safety.

Effect of multidose drug dispensing on the time in therapeutic range in patients using vitamin-K antagonists: A randomized controlled trial

BACKGROUND

A high number of vitamin K antagonist (VKA) users have a low proportion of time in therapeutic range (TTR) resulting in a high number of bleeding and thromboembolism events.

OBJECTIVE

Can the quality of anticoagulation be improved by dispensing VKAs via multidose drug dispensing (MDD).

METHOD

A randomized controlled trial in the Netherlands. Patients who used VKAs, ≥65 years of age with a TTR <65% were eligible for inclusion. All oral drugs were dispensed via MDD. In MDD systems, all oral chronic medication intended for one dosing moment is packed in plastic disposable pouches. Controls received VKAs by manual dispensing. The difference in TTR between the 6 months after- and 6 months before the index date. A mixed-effects model with the intervention, TTR before the index date, MDD system at baseline as covariates, and pharmacy as random effect. A per-protocol analysis was performed with all patients who completed the study as intended.

RESULTS

One hundred and seventy-nine patients were included. Mean age was 80.0 (SD 6.9) years. Mean TTR during the study was 79.2 ± 18.0% in the intervention group and 72.5 ± 20.1% in the control group. The intervention resulted in a 5.6% (95% CI: 0.1-11.1) increase in TTR compared to the control group. Per-protocol analysis resulted in an 8.3% (95% CI: 0.99-15.61) increase in TTR compared to the control group. No differences in reduction were observed between the intervention and control group.

CONCLUSION

The quality of anticoagulation can be improved with the use of MDD systems.

Type 2 Diabetes, Atrial Fibrillation, and Direct Oral Anticoagulation

Type 2 diabetes (T2D) is an independent risk factor of stroke and systemic embolism in patients with atrial fibrillation (AF), and T2D patients with AF-associated stroke seem to have worse clinical outcome and higher risk of unfavorable clinical course compared to individuals without this metabolic disorder. Long-term anticoagulation is indicated in majority of T2D patients with AF to prevent adverse AF-associated embolic events. Direct oral anticoagulants (DOACs), direct oral thrombin inhibitor dabigatran, and direct oral factor Xa inhibitors, rivaroxaban, apixaban, and edoxaban, have emerged as a preferred choice for long-term prevention of stroke in AF patients offering potent and predictable anticoagulation and a favorable pharmacology with low risk of interactions. This article reviews the current data regarding the use of DOACs in individuals with T2D and AF.

Precision dosing of warfarin: open questions and strategies

Warfarin has a very narrow therapeutic window and obvious interindividual variability in its effects, with many factors contributing to the body's response. Algorithms incorporating multiple genetic, environment and clinical factors have been established to select a precision dose for each patient. A number of randomized controlled trials (RCTs) were conducted to explore whether patients could benefit from these algorithms; however, the results were inconsistent. Some questions remain to be resolved. Recently, new genetic and non-genetic factors have been discovered to contribute to variability in optimal warfarin doses. The results of further RCTs have been unveiled, and guidelines for pharmacogenetically guided warfarin dosing have been updated. Based on these most recent advancements, we summarize some open questions in this field and try to propose possible strategies to resolve them.

Triple therapy after PCI - Warfarin treatment quality and bleeding risk

Background

A combination of warfarin, aspirin and clopidogrel is indicated after percutaneous coronary intervention (PCI) in some patients, despite the higher risk of bleeding inferred by this triple therapy.

Objectives

Whether the treatment quality of warfarin measured by iTTR (individual time within therapeutic INR range) is associated with bleeding complications during triple therapy after PCI.

Methods

A retrospective register study consisting of 601 triple treated PCI patients from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR). The cohort was cross-matched with the Swedish Patient Registry for background characteristics and bleeding complications up to 6 months after PCI using ICD10 codes, the Prescribed Drug Registry for ongoing medications, and the national oral anticoagulation registry Auricula for warfarin treatment quality. The patients were grouped into four iTTR groups: <50%, 50–69.9%, 70–84.9% and >85% as well as iTTR above or below 70%.

Results

Of 601 patients, 39 (6.5%) had a bleeding complication (type 2 according to BARC). Bleeding was more common for iTTR<70% compared to iTTR>70%, 28 (9.3%) vs. 11 (3.7%) (p = 0.005). The bleeding frequency increased gradually from the best group, iTTR>85% with four bleeders (3.3%) up to 17 bleeders (13.3%) in the worst group with iTTR<50% (p = 0.003), with a corresponding bleeding rate per 100 treatment years of 8.0 and 44.9, respectively. In multivariate analysis low BMI, HR 1.11 (95% CI 1.01–1.22), a medical history of anemia HR 3.17 (1.16–8.69) and iTTR < 70% HR 2.86 (1.25–6.53) increased the risk of bleeding.

Conclusion

Triple therapy after PCI confers a high risk of bleeding events. Warfarin treatment quality measured by iTTR as well as a medical history of anemia are strong independent predictors of bleeding in these patients. Physicians should pay more attention to iTTR after PCI.

Long-Term Statin Administration Does Not Affect Warfarin Time in Therapeutic Range in Australia or Singapore

BACKGROUND

Warfarin requires ongoing monitoring of the International Normalised Ratio (INR). This is because numerous factors influence the response, including drug interactions with commonly-prescribed medications, such as statins. The administration of statins with warfarin may change INR; however, there is limited information regarding the effects on warfarin control as measured by time in therapeutic range (TTR). Statins may also alter bleeds with warfarin, but there are conflicting reports demonstrating both increased and decreased bleeds, and limited data on diverse ethnic populations. Therefore, the aim of this study was to determine the effect of statin administration on warfarin control and bleeds in patients in Australia and Singapore.

METHODS

Retrospective data were collected for patients on warfarin between January and June 2014 in Australia and Singapore. Patient data were used to calculate TTR and bleed events. Concurrent statin therapy was assessed and comparisons of TTR and bleed incidence were made across patient subgroups.

RESULTS

Warfarin control in Australia and Singapore was not significantly affected by statins, as measured by TTR (83% and 58%, respectively), frequency of testing, and warfarin doses. In Australia, statin use did not significantly affect bleeds, whilst in Singapore the bleed incidence was significantly lower for patients on statins.

CONCLUSIONS

Chronic concurrent administration of statins with warfarin does not adversely affect warfarin TTR in Australia or Singapore. In Singapore, patients on statins, compared to no statins, had a lower bleed incidence and this requires further investigation, especially given the potential genetic influences of ethnicity on both statin and warfarin metabolism.

Impact of GGCX polymorphisms on warfarin dose requirements in atrial fibrillation patients

Background/aim: Warfarin is a common anticoagulant with large interindividual differences and a narrow therapeutic range. The polymorphisms of gamma-glutamyl carboxylase (GGCX) are important genetic factors for warfarin dose requirements. Materials and methods: Polymerase chain reaction and direct sequencing methods were used to detect the GGCX rs699664 genotype in 215 atrial fibrillation (AF) patients with warfarin administration. The effects on warfarin dose by different genotypes were analyzed. A warfarin dosing algorithm was developed based on age, height, CYP2C9, VKORC1, and GGCX genotype. Results: In 215 AF patients, there were 104 cases of wild-type GG genotype (48.4%), 92 cases of GA genotype (42.8%), and 19 cases of AA genotype (8.8%). Patients with the GGCX rs699664 A allele (GA or AA genotypes) needed higher warfarin doses than those with the GG genotype (P < 0.05). A warfarin dosing algorithm showed that age, height, CYP2C9, VKORC1, and GGCX genotype were the best variables for estimating warfarin dose (R2 = 41.2%). Another independent cohort of 60 AF patients showed a significant linear correlation between predicted warfarin maintenance dose and actual dose (R = 0.660, P < 0.01). Conclusion: AF patients with the GA and AA genotypes in GGCX rs699664 required significantly higher warfarin doses. GGCX rs699664 is a potential predictor for the warfarin dose of AF patients.

Antiphospholipid Syndrome On Cloud (APSOnCloud): web-based monitoring of oral anticoagulation

Antiphospholipid Syndrome (APS) is an autoimmune disease characterized by recurrent thromboses and fetal losses with the presence of antiphospholipid antibodies. The main treatment to prevent recurrent thrombotic events is oral anticoagulation with vitamin K antagonist (VKA), which requires frequent monitoring and dosage adjustments. Outpatient anticoagulation monitoring has its limitations, such as patients spending long hours between the testing procedure and waiting for the results to be adjusted. To optimize this adjustment and to improve APS patients-doctors relationship, we developed a website to help monitor APS patients, called Antiphospholipid Syndrome On Cloud or APSOnCloud. To test it, since March 2014 to March 2016, we registered 20 patients with APS that have inserted 132 international normalized ratio (INR) values. Sixty two percent were out of range and it took on average 7 hours for the doctor in charge to adjust these values. The mean time in therapeutic range was 58.1%. Our preliminary experience in monitoring VKA oral anticoagulation on APSOnCloud suggests that patients with APS might benefit from this web-based monitoring.

Elevated International Normalized Ratio in a Patient Taking Warfarin and Mauby: A Case Report

We describe a 70-year-old Haitian man who had been taking warfarin for 5 years for atrial fibrillation and pulmonary hypertension. This patient had his international normalized ratio (INR) checked in the pharmacist-run anticoagulation clinic and was followed monthly. Prior to the interaction, his INR was therapeutic for 5 months while taking warfarin 10.5 mg/d. The patient presented with an INR > 8.0. Patient held 4 days of warfarin and restarted on warfarin 8.5 mg/d. Two weeks later, his INR was 2.5. After continuing dose, patient presented 2 weeks later and INR was 4.8. Upon further questioning, the patient stated he recently began ingesting mauby. Mauby is a bitter dark liquid extracted from the bark of the mauby tree that is commonly used in the Caribbean population as a folk remedy with many health benefits. This case report illustrates that mauby may have a probable drug-herb interaction (Naranjo Algorithm Score of 6) when given with warfarin. There is a lack of published literature and unclear information on the Internet describing the interaction of mauby and warfarin. Health professionals should be cautious regarding interactions between warfarin and mauby until the interaction is fully elucidated.

Appropriateness of Dabigatran and Rivaroxaban Prescribing for Hospital Inpatients

BACKGROUND

Recent approval of the new oral anticoagulants dabigatran and rivaroxaban has led to rapid changes in anticoagulant prescribing practices. Postmarketing reports have highlighted safety concerns with these agents, and their use outside of evidence-based recommendations was noted at the authors' centre.

OBJECTIVES

To determine the incidence of and risk factors associated with inappropriate prescribing of dabigatran and rivaroxaban.

METHODS

This retrospective cohort study investigated randomly selected dabigatran or rivaroxaban prescriptions for patients admitted to a tertiary teaching hospital between January 2010 and December 2012. Appropriateness of prescribing was determined from the documented indication, drug dosage, patient's renal function, and presence of drug interactions, if applicable.

RESULTS

Among a total of 321 medication orders reviewed, the incidence of inappropriate use was 31.2% (34/109) for dabigatran and 26.9% (57/212) for rivaroxaban. Of the 97 reasons for inappropriate use that were identified, the most common were prescribing for an unapproved indication (49/97 [50.5%]), concomitant prescribing of another anticoagulant (22/97 [22.7%]), and high prescribed dose (9/97 [9.3%]). The prescribing service was found to be an independent risk factor for inappropriate prescribing (p = 0.041). Corrections were made to 23.1% (21/91) of the incorrect regimens before hospital discharge. In a sensitivity analysis using calculated ideal body weight to estimate renal function, the overall incidence of inappropriate prescribing increased to 31.5% (101/321).

CONCLUSIONS

The proportion of patients with inappropriate prescribing of dabigatran or rivaroxaban in clinical practice was higher than expected. Educational interventions and pharmacy-led initiatives with a focus on appropriate indications, concomitant anticoagulant prescribing, and review of dosage regimens are recommended to improve patient safety.

Elevated International Normalized Ratio values in a patient receiving warfarin and ceftaroline

PURPOSE

The case of a patient whose International Normalized Ratio (INR) became elevated due to a probable interaction between ceftaroline and warfarin is reported.

SUMMARY

A 65-year-old African-American man developed an INR of >18.0 after completing 12 days of ceftaroline therapy for the treatment of cellulitis while taking warfarin therapy. The patient was on warfarin due to his history of deep vein thrombosis of a lower extremity and pulmonary embolism, and his INR was consistently therapeutic for approximately 2 years before ceftaroline therapy. The patient reported no known drug allergies, had no history of adverse drug reactions, and had no recent changes in medications or diet. Phytonadione was administered, and the patient's INR began to decrease, returning to a therapeutic range of 2.30 after approximately 48 hours, at which time warfarin was restarted. After six days of hospitalization, the patient was discharged on his previous regimen of warfarin 7.5 mg orally once daily, with a therapeutic INR of 2.11. His cellulitis had resolved, so no further antibiotic therapy was warranted. To determine the likelihood of the drug interaction between warfarin and ceftaroline in this patient, the Drug Interaction Probability Scale of Horn and colleagues was applied and yielded a score of 6, indicating a probable likelihood of an interaction. Rechallenge was not attempted, as the patient's cellulitis had resolved and there were no evident signs or symptoms of infection.

CONCLUSION

A 65-year-old man experienced an increase in INR values after the addition of ceftaroline to his medication regimen.

Meta-analysis of Randomized Controlled Trials of Genotype-Guided vs Standard Dosing of Warfarin

BACKGROUND

Warfarin is a widely prescribed anticoagulant, and its effect depends on various patient factors including genotypes. Randomized controlled trials (RCTs) comparing genotype-guided dosing (GD) of warfarin with standard dosing have shown mixed efficacy and safety outcomes. We performed a meta-analysis of all published RCTs comparing GD vs standard dosing in adult patients with various indications of warfarin use.

METHODS

We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and relevant references for English language RCTs (inception through March 2014). We performed the meta-analysis using a random effects model.

RESULTS

Ten RCTs with a total of 2,505 patients were included in the meta-analysis. GD compared with standard dosing resulted in a similar % time in therapeutic range (TTR) at ≤ 1 month follow-up (39.7% vs 40.2%; mean difference [MD], -0.52 [95% CI, -3.15 to 2.10]; P = .70) and higher % TTR (59.4% vs 53%; MD, 6.35 [95% CI, 1.76-10.95]; P = .007) at > 1 month follow-up, a trend toward lower risk of major bleeding (risk ratio, 0.46 [95% CI, 0.19-0.1.11]; P = .08) at ≤ 1 month follow-up and lower risks of major bleeding (0.34 [95% CI, 0.16-0.74], P = .006) at > 1-month follow-up, and shorter time to maintenance dose (TMD) (24.6 days vs 34.1 days; MD, -9.54 days [95% CI, -18.10 to -0.98]; P = .03) at follow-up but had no effects on international normalized ratio [INR] > 4.0, nonmajor bleeding, thrombotic outcomes, or overall mortality.

CONCLUSIONS

In the first month of genotype-guided warfarin therapy, compared with standard dosing, there were no improvements in % TTR, INR > 4.0, major or minor bleeding, thromboembolism, or all-cause mortality. There was a shorter TMD, and, after 1 month, improved % TTR and major bleeding incidence, making this a cost-effective strategy in patients requiring longer anticoagulation therapy.

Patient–health care provider relationship: how can it impact on APS (Hughes’ syndrome) adherence to treatment?

Adherence to treatment is fundamental for its success. It comprises compliance combined with persistency and should be constantly reassessed. This is true in all medical situations. In antiphospholipid syndrome (or Hughes’ syndrome), in addition to taking the medication at the planned time so that its effect on blood can be assessed and the dose adjusted if necessary, all patients must incorporate healthy habits with a treatment that is lifelong and will be influenced by dietary changes and the use of many other medications. Following a regime for the treatment to be effective, and to avoid serious complications, often creates the sensation of ‘living on a tightrope’ for both the patients and the health care providers. Patient education along with constant monitoring using proper communication settings and tools are certain to improve adherence and outcomes.

The quality of oral anticoagulation in general practice in patients with atrial fibrillation

BACKGROUND

The aims of this study were to evaluate the quality of oral anticoagulation (OAC) in AF patients in the practices of general practitioners (GPs) in Germany and to investigate possible causal factors which influence OAC quality.

METHODS

We conducted a multi-center, non-interventional, prospective observational cohort study among general practitioners (GPs) in Germany. To assess the quality of OAC on the basis of the prospectively documented international normalized ratio (INR) values, the time in therapeutic range (TTR) was calculated using the Rosendaal linear trend method. The causes of poor OAC quality were identified by a multivariate analysis model (logistical regression; poor OAC quality: TTR <60%).

RESULTS AND CONCLUSIONS

For 525 OAC patients (66.8%; patients with at least 2 prospectively documented INR values) the average TTR (target range of 2.0-3.0) was 67.6%. About 34.7% of the patients had a TTR <60%. None of the variables representing characteristics of the medical practices were capable of explaining the occurrence of poor OAC quality. However, with regard to care provision-based variables, the existence of a brief discontinuation of medication was important. As the existence of adherence barriers increased, the probability of poor anticoagulation quality increased. In conclusion, the provision of OAC in the German health care system is to be regarded as good, but far from ideal. Our causal analysis shows that patient-based factors should be addressed through the provision of improved training and that the rationale behind the interruption of OAC treatment should be critically examined.

Practical use of dabigatran etexilate for stroke prevention in atrial fibrillation

Atrial fibrillation (AF) is associated with an increased risk of thromboembolism, and is the most prevalent factor for cardioembolic stroke. Vitamin K antagonists (VKAs) have been the standard of care for stroke prevention in patients with AF since the early 1990s. They are very effective for the prevention of cardioembolic stroke, but are limited by factors such as drug-drug interactions, food interactions, slow onset and offset of action, haemorrhage and need for routine anticoagulation monitoring to maintain a therapeutic international normalised ratio (INR). Multiple new oral anticoagulants have been developed as potential replacements for VKAs for stroke prevention in AF. Most are small synthetic molecules that target thrombin (e.g. dabigatran etexilate) or factor Xa (e.g. rivaroxaban, apixaban, edoxaban, betrixaban, YM150). These drugs have predictable pharmacokinetics that allow fixed dosing without routine laboratory monitoring. Dabigatran etexilate, the first of these new oral anticoagulants to be approved by the United States Food and Drug Administration and the European Medicines Agency for stroke prevention in patients with non-valvular AF, represents an effective and safe alternative to VKAs. Under the auspices of the Regional Anticoagulation Working Group, a multidisciplinary group of experts in thrombosis and haemostasis from Central and Eastern Europe, an expert panel with expertise in AF convened to discuss practical, clinically important issues related to the long-term use of dabigatran for stroke prevention in non-valvular AF. The practical information reviewed in this article will help clinicians make appropriate use of this new therapeutic option in daily clinical practice.

Antithrombotics for stroke prevention in non-valvular atrial fibrillation: an update

Nurses and nurse practitioners play an integral role in initiating and managing antithrombotic prophylaxis in patients with atrial fibrillation (AF). Since the advent of warfarin in the 1950s, there have been few changes in this field until recently. Warfarin has been used for decades and has well-demonstrated efficacy. However, it also has well-known drawbacks, including an unpredictable dose response, need for anticoagulation monitoring, frequent dose adjustments, and many drug and food interactions. A new generation of anticoagulants, which includes direct thrombin inhibitors and selective Factor Xa inhibitors, shows the potential to significantly improve options for antithrombotic prophylaxis and to positively affect patient outcomes. The objective of this review is to update nurses on the new oral anticoagulants, other recent developments, such as improved risk-assessment techniques, and the role of over-the-counter products, including aspirin.

Hemarthrosis in a patient on warfarin receiving ceftaroline: a case report and brief review of cephalosporin interactions with warfarin

OBJECTIVE

To report a possible interaction between warfarin and ceftaroline, resulting in hemarthrosis, and provide readers with an understanding of mechanisms of interaction between cephalosporins and warfarin.

CASE SUMMARY

Ceftaroline was prescribed for an 85-year-old female with a therapeutic international normalized ratio (INR) hospitalized for the treatment of cellulitis. She was subsequently readmitted with shoulder pain and a supratherapeutic INR. The patient was diagnosed with hemarthrosis, presumably related to elevated INR. Evaluation using the drug interaction probability scale for warfarin and ceftaroline yielded a score consistent with a possible or probable interaction.

DISCUSSION

Cephalosporins may interact with warfarin through a variety of mechanisms, including potentiation of hypoprothrombinemia related to certain side chain groups, inhibition of P-glycoprotein, or alteration of gastrointestinal flora. All mechanisms reported in the medical literature as of April 2012 are briefly examined, but the latter is the most reasonable mechanism for a ceftaroline interaction with warfarin.

CONCLUSIONS

Health care providers should consider closely monitoring patients receiving antibiotics with activity against Enterobacteriaceae and warfarin, even if no direct mechanism of interaction has been reported. Further research regarding a ceftaroline-warfarin interaction is warranted.

Treatment of warfarin-associated coagulopathy with vitamin K

Warfarin is the most common form of oral anticoagulant therapy. Although it has indisputable benefit in the management of thromboembolic disease, warfarin-associated coagulopathy (WAC) is a well-documented complication of its use. As warfarin exerts its effect by impairing formation of the vitamin K-dependent clotting factors, a cornerstone of WAC management is vitamin K replacement. Daily vitamin K supplementation is an emerging approach to regulate international normalized ratios in difficult-to-control patients. Mild WAC without bleeding can often be managed with warfarin withdrawal alone. For excessive international normalized ratio elevation in the absence of bleeding, low-dose oral vitamin K (1?2.5 mg) is sufficient and achieves the same degree of international normalized ratio correction by 24 h as intravenous therapy. The stable patient with WAC and minor bleeding can also be given oral vitamin K, with correction of the underlying defect. Major bleeding should first be managed with factor replacement for immediate correction of the coagulopathy, using either a prothrombin complex concentrate or fresh-frozen plasma. High-dose vitamin K (10 mg) should be given concurrently via intravenous infusion to confer lasting correction. Warfarin resistance and vitamin K-associated anaphylaxis are rare. Despite development of new oral anticoagulant therapy compounds, warfarin will probably retain a prominent role in thromboembolism management for several years to come.