Warfarin therapy: in need of improvement after all these years

Beyond Anticoagulation: A Comprehensive Review of Non-Vitamin K Oral Anticoagulants (NOACs) in Inflammation and Protease-Activated Receptor Signaling

Non-vitamin K oral anticoagulants (NOACs) have revolutionized anticoagulant therapy, offering improved safety and efficacy over traditional agents like warfarin. This review comprehensively examines the dual roles of NOACs-apixaban, rivaroxaban, edoxaban, and dabigatran-not only as anticoagulants, but also as modulators of inflammation via protease-activated receptor (PAR) signaling. We highlight the unique pharmacotherapeutic properties of each NOAC, supported by key clinical trials demonstrating their effectiveness in preventing thromboembolic events. Beyond their established anticoagulant roles, emerging research suggests that NOACs influence inflammation through PAR signaling pathways, implicating factors such as factor Xa (FXa) and thrombin in the modulation of inflammatory responses. This review synthesizes current evidence on the anti-inflammatory potential of NOACs, exploring their impact on inflammatory markers and conditions like atherosclerosis and diabetes. By delineating the mechanisms by which NOACs mediate anti-inflammatory effects, this work aims to expand their therapeutic utility, offering new perspectives for managing inflammatory diseases. Our findings underscore the broader clinical implications of NOACs, advocating for their consideration in therapeutic strategies aimed at addressing inflammation-related pathologies. This comprehensive synthesis not only enhances understanding of NOACs' multifaceted roles, but also paves the way for future research and clinical applications in inflammation and cardiovascular health.

Factor Xa inhibitors vs. warfarin in patients with Hughes syndrome: a systematic review and meta-analysis of randomized controlled trials

Background

The optimal treatment regimen for patients with Hughes syndrome remains unclear. Therefore, the authors sought to compare the outcomes of warfarin vs. factor Xa inhibitors in patients with Hughes syndrome.

Methods

MEDLINE, Embase, and Cochrane Central databases were searched for randomized controlled trials (RCTs) comparing 8 efficacy and safety of warfarin and factor Xa inhibitors in patients with Hughes syndrome. Recurrent thrombosis, all-cause mortality, stroke, adverse reactions, and bleeding were among 10 outcomes of interest. Mantel-Haenszel weighted random-effects model was used to calculate 11 relative risks (RRs) with 95% CIs.

Results

The analysis included 625 patients from four RCTs and one post-hoc analysis. Meta-analysis showed a statistically non-significant difference between factor Xa inhibitors and warfarin in the recurrent thrombosis risk (arterial or venous) [RR 2.77 (95%, CI 0.79, 9.65); P=0.11, I2=50%]. Consistent results were revealed among patients with a previous history of arterial thrombosis [RR 2.76 (95% CI 0.93, 8.16); P=0.75, I2=0%], venous thrombosis [RR 1.71 (95% CI 0.60, 4.84); P=0.31, I2=15%] and patients who were triple antiphospholipid antibodies (aPL) positive [RR 4.12 (95% CI 0.46, 37.10); 21 P=0.21, I2=58%]. Factor Xa inhibitors were significantly associated with an increased risk of stroke [RR 8.51 (95% CI 2.35, 13.82); P=0.47, I2=0%].

Conclusion

Factor Xa inhibitors exhibited an increased risk of stroke among patients with Hughes syndrome. In addition, although not significant, the higher RRs among patients on factor Xa inhibitors may indicate a higher risk of thrombotic events associated with factor Xa inhibitors.

Development and validation of the Chinese oral anticoagulants knowledge tool (C-OAKT): A pilot study

Objective

To develop and validate an oral anticoagulant knowledge tool for Chinese-speaking patients treated with warfarin or direct oral anticoagulants (DOACs) in Hong Kong.

Method

This pilot validation study consisted of the following three phases: (1) the development of a knowledge tool and content validity assessment; (2) a pilot study of 200 participants, consisting of 100 patients taking warfarin or DOACs, 50 pharmacists, and 50 members of the general public; and (3) known-group validity and reliability assessments.

Results

A 19-item "Chinese Oral Anticoagulants Knowledge Tool (C-OAKT)" was developed with a scale content validity index of 0.95. The mean score for known-group validity was significantly higher in the pharmacist group than the patient groups, and the patient groups scored significantly higher than the general public (mean ± standard deviation [SD] = 90.00 ± 7.11 vs. 51.55 ± 17.49 vs. 19.0 ± 15.42, respectively; p < 0.001). The mean score was higher for patients who attended a pharmacist-managed anticoagulant therapy management clinic (PAC) than for non-PAC patients (mean ± SD = 56.80 ± 13.60 vs. 46.30 ± 9.43; p = 0.004). An analysis of internal consistency showed a Cronbach's alpha value of 0.86.

Conclusion

The results of the pilot validation study suggested that the C-OAKT is a valid and reliable instrument for assessing patients' knowledge of oral anticoagulants in ambulatory care settings.

Innovations

This is the first validated Chinese version of an anticoagulant knowledge assessment tool. This tool will be utilized in public hospitals in Hong Kong, and will facilitate future research exploring the relationship between anticoagulant knowledge and patient-related outcomes.

Evaluation of Machine Learning Approaches for Predicting Warfarin Discharge Dose in Cardiac Surgery Patients: Retrospective Algorithm Development and Validation Study

BACKGROUND

Warfarin dosing in cardiac surgery patients is complicated by a heightened sensitivity to the drug, predisposing patients to adverse events. Predictive algorithms are therefore needed to guide warfarin dosing in cardiac surgery patients.

OBJECTIVE

This study aimed to develop and validate an algorithm for predicting the warfarin dose needed to attain a therapeutic international normalized ratio (INR) at the time of discharge in cardiac surgery patients.

METHODS

We abstracted variables influencing warfarin dosage from the records of 1031 encounters initiating warfarin between April 1, 2011, and November 29, 2019, at St Michael's Hospital in Toronto, Ontario, Canada. We compared the performance of penalized linear regression, k-nearest neighbors, random forest regression, gradient boosting, multivariate adaptive regression splines, and an ensemble model combining the predictions of the 5 regression models. We developed and validated separate models for predicting the warfarin dose required for achieving a discharge INR of 2.0-3.0 in patients undergoing all forms of cardiac surgery except mechanical mitral valve replacement and a discharge INR of 2.5-3.5 in patients receiving a mechanical mitral valve replacement. For the former, we selected 80% of encounters (n=780) who had initiated warfarin during their hospital admission and had achieved a target INR of 2.0-3.0 at the time of discharge as the training cohort. Following 10-fold cross-validation, model accuracy was evaluated in a test cohort comprised solely of cardiac surgery patients. For patients requiring a target INR of 2.5-3.5 (n=165), we used leave-p-out cross-validation (p=3 observations) to estimate model performance. For each approach, we determined the mean absolute error (MAE) and the proportion of predictions within 20% of the true warfarin dose. We retrospectively evaluated the best-performing algorithm in clinical practice by comparing the proportion of cardiovascular surgery patients discharged with a therapeutic INR before (April 2011 and July 2019) and following (September 2021 and May 2, 2022) its implementation in routine care.

RESULTS

Random forest regression was the best-performing model for patients with a target INR of 2.0-3.0, an MAE of 1.13 mg, and 39.5% of predictions of falling within 20% of the actual therapeutic discharge dose. For patients with a target INR of 2.5-3.5, the ensemble model performed best, with an MAE of 1.11 mg and 43.6% of predictions being within 20% of the actual therapeutic discharge dose. The proportion of cardiovascular surgery patients discharged with a therapeutic INR before and following implementation of these algorithms in clinical practice was 47.5% (305/641) and 61.1% (11/18), respectively.

CONCLUSIONS

Machine learning algorithms based on routinely available clinical data can help guide initial warfarin dosing in cardiac surgery patients and optimize the postsurgical anticoagulation of these patients.

Anticoagulation for Stroke Prevention of Concomitant Atrial Fibrillation and End-Stage Renal Disease: Insights of Cardiologists and Nephrologists From India

Introduction Patients with concomitant atrial fibrillation (AF) and end-stage renal disease (ESRD) are at increased risk of thrombosis and bleeding. Diligent anticoagulant therapy that prevents major bleeding is essential for stroke prevention. There is a dearth of evidence and guidance on anticoagulation in this patient subset. Methods A validated questionnaire was sent to 500 physicians across India. Anonymized responses from 353 consenting physicians (275 cardiologists and 78 nephrologists) were analyzed. Results Most physicians opined that the risk of progression of chronic kidney disease (CKD) stages 2-4 to ESRD was 1-5%, and that >10% of patients with ESRD had concomitant AF. Most physicians perceived that the risk of ischemic stroke, major bleeding, and mortality was 30-40%, <15%, and >40% respectively in patients with concomitant AF and ESRD. The first critical goal for the management of these patients was 'reduction of thrombotic risk', followed by 'prevention of bleeding' and finally 'prevention of ESRD progression' (72.0%, 68.0%, and 67.1% participants, respectively). Most participating physicians (93.8%) preferred non-vitamin K antagonist oral anticoagulants (NOACs) over warfarin for stroke prevention, and most of the participating physicians (94.9%) preferred an adjusted dose rather than the standard dose of the NOAC. Most of the responses were similar between cardiologists and nephrologists. Conclusion According to the survey response, patients with concomitant AF and ESRD have an increased risk of thrombosis, bleeding, and mortality. NOACs with dose adjustment are the preferred modality for stroke prevention among cardiologists and nephrologists in India, with the primary goal of preventing thrombotic events.

A systematic review and meta-analysis of non-vitamin K antagonist oral anticoagulants vs vitamin K antagonists after transcatheter aortic valve replacement in patients with atrial fibrillation

PURPOSE

Transcatheter aortic valve replacement (TAVR) is increasingly carried out in patients with aortic valvular conditions. Atrial fibrillation (AF) is a common comorbidity among patients undergoing TAVR. Despite this, there remains a paucity of data and established guidelines regarding anticoagulation use post-TAVR in patients with AF.

METHODS

Four databases were searched from inception until 12 October 2021. A title and abstract sieve, full-text review and data extraction were conducted by independent authors, and articles including patients without AF were excluded. The Review Manager (Version 5.4) was utilised in data analysis.

RESULTS

A total of 25,199 post-TAVR patients with AF were included from seven articles, with 9764 patients on non-vitamin K antagonist oral anticoagulants (NOAC) and 15,435 patients on vitamin K antagonists (VKA). In this analysis, there was a significantly lower risk of all-cause mortality at 1 year (RR: 0.75, CI: 0.58-0.97, p = 0.04, I² = 56%), and bleeding at 1 year (RR: 0.73, CI: 0.68-0.79, p =  < 0.00001, I² = 0%), between patients on NOAC and VKA. There were no detectable differences between patients on NOAC and VKA for all-cause mortality at 2 years, stroke within 30 days, stroke within 1 year, ischaemic stroke at 1 year and life-threatening bleeding at 30 days.

CONCLUSION

While the results of this analysis reveal NOAC as a potential alternate treatment modality to VKA in post-TAVR patients with AF, further research is needed to determine the full safety and efficacy profile of NOAC (PROSPERO: CRD42021283548).

Influence of Vitamin D Status on the Maintenance Dose of Warfarin in Patients Receiving Chronic Warfarin Therapy

INTRODUCTION

Considering the anticoagulant actions of vitamin D, we hypothesize that vitamin D status might affect the required dose of warfarin for maintaining the therapeutic international normalized ratio (INR).

METHODS

In a retrospective single-center cohort study, serum levels of 25-hydroxyvitamin D were assessed for 89 subjects receiving a stable dose of warfarin for 3 months or longer and had a stable INR between 2 and 3.5 for at least three consecutive visits. A warfarin sensitivity index (WSI), defined as the steady-state INR divided by the mean daily warfarin dose, was used for measuring the warfarin dose response. The relation between the serum level of 25-hydroxyvitamin D and WSI value and the difference in the mean WSI value between the subjects with different vitamin D status categories (sufficient, insufficient, and deficient) were assessed.

RESULTS

Twenty-one subjects had vitamin D deficiency, 43 had vitamin D insufficiency, and only 25 had normal levels of 25-hydroxyvitamin D. Based on the multiple linear regression analysis, there was a significant but weakly positive correlation between WSI and 25-hydroxyvitamin D serum levels, as the value of WSI increases by almost 0.0027434 for every unit increase in 25-hydroxyvitamin D serum level (p value = 0.041). Using one-way ANOVA analysis, there was a trend in a significant difference between the groups with different vitamin D status categories regarding the mean WSI value (F = 2.95, p value = 0.057), as subjects with sufficient vitamin D state compared to those with vitamin D deficiency had a higher WSI value.

CONCLUSIONS

Although the study's limitations limit our ability to draw definite conclusions, the present data suggest that in addition to other traditional factors, vitamin D status might also affect warfarin sensitivity and maintenance dose requirement. However, to more clearly explain this link, further studies with high involvement subjects are required.

Profiling of warfarin pharmacokinetics-associated genetic variants: Black Africans portray unique genetic markers important for an African specific warfarin pharmacogenetics-dosing algorithm

BACKGROUND

Warfarin dose variability observed in patients is attributed to variation in genes involved in the warfarin metabolic pathway. Genetic variation in CYP2C9 and VKORC1 has been the traditional focus in evaluating warfarin dose variability, with little focus on other genes.

OBJECTIVE

We set out to evaluate 27 single nucleotide polymorphisms (SNPs) in the CYP2C cluster loci and 8 genes (VKORC1, ABCB1, CYP2C9, CYP2C19, CYP2C8, CYP1A2, CYP3A4, and CYP3A5) involved in pharmacokinetics of warfarin.

PATIENTS/METHODS

503 participants were recruited among black Africans and Mixed Ancestry population groups, from South Africa and Zimbabwe, and a blood sample taken for DNA. Clinical parameters were obtained from patient medical records, and these were correlated with genetic variation.

RESULTS

Among black Africans, the SNPs CYP2C rs12777823G>A, CYP2C9 c.449G>A (*8), CYP2C9 c.1003C>T (*11) and CYP2C8 c.805A>T (*2) were significantly associated with warfarin maintenance dose. Conversely, CYP2C9 c.430C>T (*2), CYP2C8 c.792C>G (*4) and VKORC1 g.-1639G>A were significantly associated with maintenance dose among the Mixed Ancestry. The presence of CYP2C8*2 and CYP3A5*6 alleles was associated with increased mean warfarin maintenance dose, whereas CYP2C9*8 allele was associated with reduced warfarin maintenance dose.

CONCLUSION

African populations present with a diversity of variants that are important in predicting pharmacogenetics-based warfarin dosing in addition to those reported in CYP2C9 and VKORC1. It is therefore important, to include African populations in pharmacogenomics studies to be able to identify all possible biomarkers that are potential predictors for drug response.

Smartphone-enabled 3D printing of medicines

3D printing is a manufacturing technique that is transforming numerous industrial sectors, particularly where it is key tool in the development and fabrication of medicinees that are personalised to the individual needs of patients. Most 3D printers are relatively large, require trained operators and must be located in a pharmaceutical setting to manufacture dosage forms. In order to realise fully the potential of point-of-care manufacturing of medicines, portable printers that are easy to operate are required. Here, we report the development of a 3D printer that operates using a mobile smartphone. The printer, operating on stereolithographic principles, uses the light from the smartphone's screen to photopolymerise liquid resins and create solid structures. The shape of the printed dosage form is determined using a custom app on the smartphone. Warfarin-loaded Printlets (3D printed tablets) of various sizes and patient-centred shapes (caplet, triangle, diamond, square, pentagon, torus, and gyroid lattices) were successfully printed to a high resolution and with excellent dimensional precision using different photosensitive resins. The drug was present in an amorphous form, and the Printlets displayed sustained release characterises. The promising proof-of-concept results support the future potential of this compact, user-friendly and interconnected smartphone-based system for point-of-care manufacturing of personalised medications.

Use of oral rivaroxaban in cerebral venous thrombosis

Background

Cerebral venous thrombosis (CVT) is an uncommon cause of stroke in humans and the mainstay of treatment is anticoagulation unless contraindicated. Non-vitamin K oral anticoagulants have not been duly evaluated in randomized controlled trials in CVT.

Objective

To compare the efficacy and safety of oral rivaroxaban with vitamin K anticoagulant (warfarin) in preventing recurrent venous thromboembolism (VTE) in patients with CVT.

Methods

Adult patients with CVT, who were stable after 5-12 days of treatment with parenteral heparin 1 mg/kg, were screened for eligibility. The patients were randomly divided into two groups to receive oral rivaroxaban 20-30 mg daily or warfarin 1, 3 or 5 mg daily (with the dose adjusted to maintain an INR of 2-3), for 3-12 months. Recanalization rates, periprocedural complications, and clinical outcomes were assessed by Magnetic Resonance Venography (MRV) and National Institutes of Health Stroke Scale (NIHSS) at 3rd, 6th and 12th month follow-ups.

Results

In total, 45 patients with CVT were randomized to the two treatment groups (21 to rivaroxaban and 24 to warfarin). Overall recanalization was achieved by 18 (86%) and 20 (83%) cases from rivaroxaban and warfarin group, respectively at 6th month follow-up; and by all 45 (100%) cases from the both groups at 12th month follow-up. Excellent outcome (NIHSS score 0) was obtained by 20 (95%) cases from rivaroxaban group at 3rd to 12th month follow-ups; and by 23 (96%) cases at 6th to 12th month follow-ups. There were no major bleeding events during the trial. None of the patients developed recurrence of thrombosis. Statistically, no significant difference between the two treatment groups in terms of recanalization and clinical outcomes could be observed.

Conclusion

Rivaroxaban is a safe option in CVT however; larger randomized controlled studies will impact the results validity.

Assessing quality of life using WHOQOL-BREF: A cross-sectional insight among patients on warfarin in Malaysia

Background and aim

The effect of anticoagulation control on overall Health-Related Quality of Life (HRQoL) in patients taking warfarin in Malaysia has not been explored yet. Therefore, this study aimed to evaluate HRQoL among patients on warfarin in Malaysia.

Methods

HRQoL among patients on warfarin was measured using WHOQOL-BREF (World Health Organization Quality of life Assessment: Brief Version). Descriptive and inferential statistical analysis was done using Statistical Package for the Social Sciences (SPSS) version 22.

Results

Out of 319 patients, more female patients were observed than the males (n = 221, 69.3%, and n = 98, 30.7% respectively). Mean scores for the physical (61.14 ± 15.96), psychological (68.58 ± 16.11), social (63.55 ± 27.06) and environmental domains (62.78 ± 17.58) were observed. Statistically, a significant association was found between the comorbidities other than CVDs with health satisfaction (p = 0.002), physical (p = 0.001), psychological (p < 0.001), social (p = 0.003) and environmental domains of the WHOQOL-BREF. A weak positive correlation between overall health satisfaction and the social domain (r = 0.153) and a moderate positive correlation between the physical and environmental domains (r = 0.628) of the WHOQOL-BREF were observed.

Conclusion

Patients had overall better perceived HRQoL scores in the psychological domain as compared with the rest of the domains of the WHOQOL-BREF. Age, gender, employment status, education level, the indication of use and duration of warfarin therapy associated with overall perceived HRQoL.

Comparative effects of telemedicine and face-to-face warfarin management: A systematic review and network meta-analysis

OBJECTIVE

To determine the comparative effects of different types of telemedicine on anticoagulation control and adverse outcomes in patients taking warfarin.

DATA SOURCES

A systematic search was conducted in PubMed, the Cochrane library, EMBASE, CINAHL, OpenGrey, and DART-Europe from inception to September 2019.

STUDY SELECTION

Randomized controlled trials, quasi-experimental and cohort studies were included if they evaluated the effect of telemedicine in patients using warfarin for 3 months or more.

METHODS

Two reviewers extracted and assessed the quality of studies by means of the Cochrane Effective Practice and Organization of Care Group. Network meta-analyses were performed using a random-effects model. Surface under the cumulative ranking curve (SUCRA) methods were used to rank different telemedicine types.

RESULTS

Of the 14,673 articles retrieved, 12 studies involving 11,478 patients met the inclusion criteria. The 5 types of telemedicine categorized were 1) laboratory draw with individual telephonic follow-up by health care (HC) providers (Lab/Tel/HC); 2) laboratory draw with individual telephonic follow-up with periodic, routine routine face-to-face (F2F) visit (Lab/Tel+F2F/HC); 3) laboratory draw with individual and group follow-up via online access (Lab/Online/HC); 4) patient self-test (PST) with telephonic or Web-based follow-up by automated management system (PST/Tel-Online/Auto); and 5) PST with telephonic follow-up by HC provider (PST/Tel/HC). PST/Tel-Online/Auto appears to be superior to F2F for TTR (mean difference 8.78%; 95% CI 0.06%-17.50%) and Lab/Online/HC for in-range INR (odds ratio 2.59; 95% CI 1.04-6.46). The SUCRAs suggested that PST/Tel-Online/Auto was preferred for both TTR and INR, at 84.2% and 93.9%, respectively, whereas Lab/Tel/HC was preferred to prevent major bleeding (74.1%) or thromboembolic event (70.7%).

CONCLUSION

According to the current evidence of uncertain quality, the best effects on anticoagulation control and adverse outcomes were achieved from different types of telemedicine. Variations in the effects of telemedicine on diverse outcomes should be considered before implementing telemedicine interventions in patients taking warfarin.

Prevalence of tablet splitting in a Brazilian tertiary care hospital

Background:

Although a highly common practice in hospital care, tablet splitting can cause dose variation and reduce drug stability, both of which impair drug therapy.

Objective:

To determine the overall prevalence of tablet splitting in hospital care as evidence supporting the rational prescription of split tablets in hospitals.

Methods:

Data collected from inpatients’ prescriptions were analyzed using descriptive statistics and used to calculate the overall prevalence of tablet splitting and the percentage of split tablets that had at least one lower-strength tablet available on the market. The associations between the overall prevalence and gender, age, and hospital unit of patients were also assessed. The results of laboratory tests, performed with a commercial splitter, allowed the calculation of the mass loss, mass variation, and friability of the split tablets.

Results:

The overall prevalence of tablet splitting was 4.5%, and 78.5% of tablets prescribed to be split had at least one lower-strength tablet on the market. The prevalence of tablet splitting was significantly associated with the patient’s age and hospital unit. Laboratory tests revealed mean values of mass loss and variation of 8.7% (SD 1.8) and 11.7% (SD 2.3), respectively, both of which were significantly affected by the presence of coating and scoreline. Data from laboratory tests indicated that the quality of 12 of the 14 tablets deviated in at least one parameter examined.

Conclusions:

The high percentage of unnecessary tablet splitting suggests that more regular, rational updates of the hospital’s list of standard medicines are needed. Also, inappropriate splitting behavior suggests the need to develop tablets with functional scores.

Determinants of health-related quality of life among warfarin patients in Pakistan

INTRODUCTION

The effect of anticoagulation control on overall Health-Related Quality of Life (HRQoL) in patients taking warfarin in Pakistan has not been explored yet. Therefore, this study aimed to evaluate HRQoL among warfarin patients in Pakistan.

METHODS

This cross-sectional study was conducted among patients on warfarin in Pakistan. By purposive sampling, data were collected using demographic data collection form and the World Health Organization Quality of Life: Brief Version (WHOQOL-BREF). The WHOQOL-BREF is comprised of four domains; physical, psychological, social relationships, and environment. Descriptive and inferential statistical analysis was done using SPSS version 22.

RESULTS

Out of 295 warfarin patients, more females than males (<0.001) were observed (n = 184, 62.4%, and n = 111, 37.6% respectively). One hundred and eighteen (40.0%) patients were less than 30-years of age, whereas one hundred and seventy-seven (60.0%) patients were above 30-years of age. Mean scores for the physical (62.44±15.36), psychological (67.84±15.54), social (64.27±26.28) and environment domains (63.45±17.66) were observed.

CONCLUSION

Patients had overall lower to moderate but satisfactory HRQoL scores in all four domains. Age, gender, employment status, education level, the indication of use and duration of warfarin therapy was associated with one or more domains of HRQoL among warfarin patients. The findings of this study would serve as a primary database for future studies. This study highlights how non-clinical factors could impact HRQoL in studied patients.

Trends in oral anticoagulant prescribing in individuals with type 2 diabetes mellitus: a population-based study in the UK

OBJECTIVE

To evaluate oral anticoagulant (OAC) prescribing trends in type 2 diabetes mellitus (T2DM) in the UK from 2001 to 2015.

DESIGN

A cross-sectional drug utilisation study.

SETTING

Electronic health records from The Health Improvement Network primary care database in the UK.

PARTICIPANTS

Individuals with T2DM who received a record of OAC prescription.

OUTCOME MEASURES

The prescribing trends of OAC medications in individuals with T2DM were examined from 2001 to 2015, stratified by age, gender and therapeutic classifications.

RESULTS

A total of 361 635 individuals with T2DM were identified, of whom 36 570 were prescribed OAC from 2001 to 2015. The prevalence of OAC prescribing increased by 50.0%, from 1781 individuals receiving OAC prescriptions (IROACP) (4.4 (95% CI 4.2 to 4.6) per 100 persons) in 2001, to 17 070 IROACP (6.6 (95% CI 6.5 to 6.7) per 100 persons) in 2015. The prevalence of warfarin prescribing decreased by 14.0%, from 1761 individuals receiving warfarin prescriptions (IRWP) (98.9 (95% CI 98.4 to 99.4) per 100 persons) in 2001, to 14 533 IRWP (85.1 (95% CI 84.6 to 85.7) per 100 persons) in 2015. This corresponded with increased prescribing of direct oral anticoagulants (DOACs), from 18 individuals receiving DOAC prescriptions (IRDOACP) (0.1 (95% CI 0.08 to 0.23) per 100 persons) in 2010, to 3016 IRDOACP (17.6 (95% CI 17.1 to 18.2) per 100 persons) in 2015, during the same period.

CONCLUSIONS

Prescribing of OACs in individuals with T2DM increased from 2001 to 2015. Since the introduction of DOACs, there has been a clear shift in prescribing towards these agents. Future studies are needed to assess the safety of coadministration of OAC medications and antidiabetic therapy with T2DM.

The Genetics of Warfarin Dose-Response Variability in Africans: An Expert Perspective on Past, Present, and Future

Coumarins such as warfarin are prescribed for prevention and treatment of thromboembolic disorders. Warfarin remains the most widely prescribed and an anticoagulant of choice in Africa. Warfarin use is, however, limited by interindividual variability in pharmacokinetics and a narrow therapeutic index. The difference in patients' pharmacodynamic responses to warfarin has been attributed to genetic variation in warfarin metabolism and molecular targets (e.g., CYP2C9 and VKORC1) and host-environment interactions. This expert review offers a synthesis of human genetics studies in Africans with respect to pharmacogenetics-informed warfarin dosing. We identify areas that need future research attention or could benefit from harnessing existing pharmacogenetics knowledge toward rational and optimal therapeutics with warfarin in African patients. A literature search was conducted until January 2019. A total of 343 articles were retrieved from nine African countries: Botswana, Ethiopia, Egypt, Ghana, Kenya, South Africa, Sudan, Tanzania, and Mozambique. We found 19 studies on genetics of warfarin treatment specifically among Africans. Genes examined included CYP2C9, VKORC1, CYP4F2, APOE, CALU, GGCX, and EPHX1. CYP2C9*2 and *3 alleles were highly frequent among Egyptians, while rare in other African populations. CYP2C9*5, *8, *9, and *11, and VKORC1 Asp36Tyr genetic variants explained warfarin variability in Africans better, compared to CYP2C9*2 and *3. In Africa, there is limited pharmacogenetics data on warfarin. Therefore, future research and funding commitments should be prioritized to ensure safe and effective use of warfarin in Africa. Lessons learned in Africa from the science of pharmacogenetics would inform rational therapeutics in hematology, cardiology, and surgical specialties worldwide.

Clinical Outcomes of Telephone Service for Patients on Warfarin: A Systematic Review and Meta-Analysis

Objective: To evaluate clinical outcomes of telephone-based service for patients on warfarin. Methods: Five bibliographic databases and gray literature were searched for articles that reported the effects of telephone interventions provided to patients using warfarin compared with those receiving usual clinic-based care. Mean difference (MD) and relative risk (RR) were used to calculate the effects of telephone intervention on time in therapeutic range (TTR) and visit in range (VIR), respectively. Adverse events (AEs) were pooled and reported as incidence rate ratios. Results: A total of 1,840 articles were examined. Eight articles involving 8,087 subjects were included in the quantitative synthesis. The pooled estimates from seven studies showed no difference on TTR between the telephone service group and the usual care group (MD 2.30; 95% confidence interval [CI] -3.56 to 8.16). In addition, VIR in the telephone service group was not different from the usual care group (RR 1.22, 95% CI 0.87-1.71). Moreover, patients in telephone service groups appeared to have a lower incidence of AEs compared with usual care groups. Discussion: Telephone-based service could be considered as an alternative anticoagulant management. However, owing to a lack of evidence from well-designed studies, further high-quality randomized control trials are warranted.

Association between four microRNA binding site-related polymorphisms and the risk of warfarin-induced bleeding complications

Bleeding is the most serious complication of warfarin anticoagulation therapy and is known to occur even at patients with therapeutic international normalized ratio (INR) range. Recently, it has been shown that microRNAs play a significant role in pharmacogenetics by regulating genes that are critical for drug function. Interaction between microRNAs and these target genes could be affected by single-nucleotide polymorphisms (SNPs) located in microRNA-binding sites. This study focused on 3′-untranslated region (3′-UTR) SNPs of the genes involved in the warfarin action and the occurrence of bleeding complications in an Iranian population receiving warfarin. A total of 526 patients under warfarin anticoagulation therapy with responding to the therapeutic dose and maintenance of the INR in the range of 2.0-3.5 in three consecutive blood tests were included in the study. Four selected 3'-UTR SNPs (rs12458, rs7294, rs1868774 and rs34669593 located in GATA4, VKORC1, CALU and GGCX genes, respectively) with the potential to disrupt/eliminate or enhance/create microRNA-binding site were genotyped using a simple PCR-based restriction fragment length polymorphism (PCR-RFLP) method. Patients with the rs12458 AT or TT genotypes of the GATA4 gene had a lower risk of bleeding compared to patients with the AA genotype (adjusted OR: 0.478, 95% CI: 0.285-0.802, P= 0.005, OR: 0.416, 95% CI: 0.192-0.902, P= 0.026, respectively). 3'-UTR polymorphisms in other genes were not significantly associated with the risk of bleeding complications. In conclusion, the SNP rs12458A>T in the 3′UTR region of GATA4 is associated with the incidence of warfarin-related bleeding at target range of INR, likely by altering microRNA binding and warfarin metabolism. Further genetics association studies are needed to validate these findings before they can be implemented in clinical settings.

Pharmacist-led medicine use review in community pharmacy for patients on warfarin

Background Medicine use review by pharmacists has the potential to improve anticoagulation therapy management in patients on warfarin. Objective To develop, implement and evaluate a pharmacist-led medication use review service for patients on warfarin. Setting Six community pharmacies in Malta. Method Patients (N = 100) aged 18 or older and on warfarin were recruited through pre-selected community-pharmacies. These patients were then invited to attend two sessions: a review session (t₁) and a follow-up session after 2 months (t₂). During the medication use review session, medication reconciliation was performed (a) to detect drug-related problems using the DOCUMENT classification system, (b) to develop an individualised care plan for each patient and (c) to recommend an action for each identified problem for physician, pharmacist or patient consideration. At t₂, the degree of acceptance of the recommendations was determined by assessing the number of drug-related problems for which action was taken to address the problem. International normalisation ration (INR) control was evaluated by calculating the percentage Time in Therapeutic Range (TTR) at t₁ and t₂ using the Rosendaal linear interpolation method. Main outcome measures Frequency and type of drug-related problems detected; percentage of accepted recommendations; and INR control. Results A total of 481 drug-related problems were identified; 40% (n = 190) were related to warfarin treatment. Need for monitoring (30%; n = 145), lack of compliance (20%; n = 97) and need for patient education (19%; n = 90) were the top three problems identified. There was a significant correlation between frequency of the problems and number of chronic medications (Spearman Correlation 0.583, p < 0.001), number of comorbidities (Spearman Correlation 0.327, p = 0.001) and older age (Spearman Correlation 0.285, p = 0.04). A total of 475 recommendations were followed-up; 49% (n = 234) were referred for consideration by the physician. The percentage of recommendations accepted (84%; n = 397) was significantly higher than the percentage of recommendations not accepted (16%; n = 78) (p < 0.001). The time in therapeutic range improved significantly from 68.7% at t₁ to 79.8% at t₂ (p = 0.01). Conclusions The high percentage of accepted recommendations and the improvement in INR control indicate that a pharmacist-led medication use review service in community pharmacy contributes to improving anticoagulation therapy management in patients on warfarin.

Warfarin Dose and CYP2C Gene Cluster: An African Ancestral-Specific Variant Is a Strong Predictor of Dose in Black South African Patients

Warfarin is a widely prescribed anticoagulant with a narrow therapeutic index. The rs12777823G>A single-nucleotide polymorphism (SNP) in the CYP2C gene cluster has been shown to influence optimal warfarin doses in African Americans. We report here effects of rs12777823G>A SNP on warfarin dose requirements in two South African population groups, black Africans (BA) and mixed ancestry (MA). A total of 425 participants on warfarin treatment were enrolled in the study. The age group of the studied population ranged between 44 and 66 years, with 69% females enrolled. Genetic characterization of the rs12777823G>A was done using the TaqMan SNP genotyping assay. To further compare effects of rs12777823G>A to those of other SNPs, VKORC1 g.-1639G>A and 4 SNPs in CYP2C9 gene (i.e., CYP2C9 c.430C>T, c.1075A>C, c.449G>A, and c.1003C>T) were analyzed. The rs12777823A variant allele frequencies were 0.28 and 0.25 in the BA and MA, respectively. The rs12777823A/A genotype was associated with significantly (p = 0.002) reduced mean warfarin dosage (27 ± 5.3 mg/week) compared with the G/G genotype (45 ± 16.1 mg/week) among BA, but not among the MA. The rs12777823G>A is located in a nongenomic region, suggesting that this SNP might be in linkage disequilibrium with another, likely causal SNP that is present in BA only. Given ongoing worldwide efforts to identify clinically relevant human genetic variation impacting on optimal warfarin dose selection, the African ancestry-specific genetic variant in the CYP2C cluster and others warrant further research and consideration in development of future warfarin dosing algorithms for precision medicine guidelines.

A Survey on the Awareness and Attitude of Physicians on Direct Oral Anticoagulants in Qatar

Direct oral anticoagulants (DOACs) are more commonly prescribed since their introduction. Reports on inappropriate prescribing have been observed which may indicate poor awareness on these agents. In this study, we aim to evaluate the extent of the physicians' knowledge on DOACs and its possible impact on physicians' confidence to prescribe these medications. A prospective cross-sectional survey was developed based on the literature review. Eligible participants were physicians and surgeons currently practicing at Hamad General Hospital in Qatar. The survey included questions on demographic and professional characteristics. It also evaluated the awareness and attitudes regarding safety, efficacy, and prescribing of DOACs. Over 6-month period, 175 practitioners responded to the survey. Overall awareness score was moderate (61% ± 18%). These scores were in alignment with participants' self-satisfaction with knowledge on DOACs (66% were not satisfied) and participants' confidence toward prescribing DOACs (48% were not confident). Age, degree of education, and years of experience had significant positive influence on awareness score. This survey indicates that practitioners have moderate awareness on DOACs. Future work should focus on reassessing practitioners' knowledge after providing well-designed education campaigns.

Anti-coagulation Drug Warfarin Contributes to Severe Adverse Outcomes in Prolonged Unsupervised Use: A Double-edged Sword

Anti-coagulation medications are widely used in clinical practice, especially in the United States as cardiac-related emergencies are on the rise. An overarching caveat in using anti-coagulation drugs as a long-term treatment regimen, such as warfarin, is that patients are closely monitored by their primary care provider. Routine monthly laboratory examinations are strictly required to assess the international normalized ratio (INR) which measures prothrombin time (PT), providing insight into how long it takes for blood to clot. A 58-year-old Caucasian male presented with non-traumatic acute quadriplegia with cord compression starting at the 3rd cervical (C3) level and continuing throughout the entire spinal cord. Radiological studies revealed severe cervical stenosis from C3 to C7 resulting from a posterior spinal mass, thoracic and lumbar spine studies revealed a compressive posterior acute epidural hematoma (EDH) compressing the thoracic spinal cord from T6 to T10 with signal change, as well as a L4-S1 posterior acute epidural hematoma compressive of the cauda equina. Upon detailed review of our patient’s history it became evident that our patient had been on a prolonged and unsupervised warfarin (Coumadin) regimen for congestive heart failure without primary care follow-up or routine laboratory testing. Our patient was a prime surgical candidate for an immediate two-stage decompression, hematoma evacuation and instrumentated fusion surgery. Post-operatively, our patient regained leg strength to 2/5 and arm strength to 4+/5.

Signals of bleeding among direct-acting oral anticoagulant users compared to those among warfarin users: analyses of the post-marketing FDA Adverse Event Reporting System (FAERS) database, 2010-2015

Purpose

To analyze and compare the signals of bleeding from the use of direct-acting oral anticoagulants (DOACs) in the US Food and Drug Administration Adverse Event Reporting System (FAERS) database over 5 years.

Methods

Reports of bleeding and of events with related terms submitted to the FAERS between October 2010 and September 2015 were retrieved and then analyzed using the reporting odds ratio (ROR). The signals of bleeding associated with DOAC use were compared with the signals of bleeding associated with warfarin use utilizing the FAERS databases.

Results

A total of 1,518 reports linked dabigatran to bleeding, accounting for 2.7% of all dabigatran-related reports, whereas 93 reports linked rivaroxaban to bleeding, which accounted for 4.4% of all rivaroxaban-related reports. The concurrent proportion of bleeding-related reports for warfarin was 3.6%, with a total of 654 reports. The association of bleeding and of related terms with the use of all three medications was significant, albeit with different degrees of association. The ROR was 12.30 (95% confidence interval [CI] 11.65–12.97) for dabigatran, 15.61 (95% CI 14.42–16.90) for warfarin, and 18.86 (95% CI 15.31–23.23) for rivaroxaban.

Conclusions

The signals of bleeding varied among the DOACs, and the bleeding signal was higher for rivaroxaban and lower for dabigatran compared to that for warfarin.

The pharmacoepigenomics informatics pipeline defines a pathway of novel and known warfarin pharmacogenomics variants

AIM

'Pharmacoepigenomics' methods informed by omics datasets and pre-existing knowledge have yielded discoveries in neuropsychiatric pharmacogenomics. Now we evaluate the generality of these methods by discovering an extended warfarin pharmacogenomics pathway.

MATERIALS & METHODS

We developed the pharmacoepigenomics informatics pipeline, a scalable multi-omics variant screening pipeline for pharmacogenomics, and conducted an experiment in the genomics of warfarin.

RESULTS

We discovered known and novel pharmacogenomics variants and genes, both coding and regulatory, for warfarin response, including adverse events. Such genes and variants cluster in a warfarin response pathway consolidating known and novel warfarin response variants and genes.

CONCLUSION

These results can inform a new warfarin test. The pharmacoepigenomics informatics pipeline may be able to discover new pharmacogenomics markers in other drug-disease systems.

Impact of warfarin discharge education program on hospital readmission and treatment costs

Background Although warfarin is highly effective, management of patients prescribed warfarin is complex due to its narrow therapeutic window. Objective To evaluate the impact of a formal warfarin discharge education program (WDEP) on hospital readmission and treatment costs in patients who received warfarin therapy. Setting Robert Wood Johnson University Hospital Somerset in Somerville, New Jersey, USA. Method In this interventional cohort study, patients were assigned to either the WDEP group or the usual care group. The effects of the WDEP on readmission within 90 days after discharge were analyzed using Cox proportional hazards models. Factors influencing treatment cost were identified using generalized linear model with log-link function and gamma distribution. Main outcome measure Hospital readmission within 90 days and treatment costs associated with hospital readmission. Results Among 692 eligible patients, 203 in each group were matched using propensity scores and there were no statistically significant differences in the patient baseline characteristics between two groups. The risk of all-cause readmission within 90 days was significantly lower in the WDEP group compared to the usual care group (relative risk = 0.46, 95% CI 0.28-0.76). The treatment costs associated with hospital readmission in the WDEP group were 19% lower than those in the usual care group after adjusting for the study variables. Conclusion A formal, individualized WDEP provided by pharmacists resulted in significant reduction of readmission and treatment costs. The economic burden of treatment costs associated with warfarin can be controlled if well-organized warfarin education is provided to patients who received warfarin therapy.

Novel venous thromboembolic disease (VTED) prophylaxis for total knee arthroplasty-aspirin and fish oil

Background

Despite the demonstrated success of multiple anticoagulation therapies for post-operative prophylaxis of thromboembolic disease in lower extremity arthroplasties, each modality comes with a unique set of limitations. Thus, the ideal anticoagulation medication which provides adequate therapy with minimal cost, complications, or added patient work is yet to be defined. One promising novel thrombophylactic supplement is fish oil, as many preliminary clinical trials have demonstrated a protective effect of fish oil against thrombosis in multiple clinical settings. In addition, others have demonstrated synergistic effect when combined with aspirin. However, there are paucity of studies that compared combined aspirin and fish oil therapy for venous thromboembolism prophylaxis with other pharmacological agents, especially in the field of orthopaedics. Therefore, this study evaluated: (I) risk of post-operative deep vein thrombosis (DVT) and pulmonary embolism (PE), and (II) bleeding complications; among patients who had primary total knee arthroplasty (TKA) and received one of the following regimens: (i) 325 mg aspirin and mechanical pulsatile stocking; (ii) rivaroxaban; or (iii) 325 mg aspirin and 1,000 mg fish oil.

Methods

This was a 6-year prospective study analyzing the postoperative thromboembolic prophylaxis received by patients who underwent primary TKA. Patients who had a previous history of thromboembolic disease were excluded from the study due to an increased risk of recurrent clot formation. A total of 850 patients were enrolled. A total of 300 patients enrolled between October 2011 and June 2013 received 325 mg aspirin and mechanical pulsatile stocking, while 250 patients enrolled between June 2013 and December 2014 received rivaroxaban. A total of 300 patients enrolled between January 2015 and July 2017 received 325 mg aspirin and 1,000 mg fish oil. Major venous thromboembolic events (VTEs) and bleeding complications within the first 90 days post-operatively were recorded in each cohort. The odds ratios (ORs) and 95% confidence intervals (CIs), for thromboembolic and bleeding events were calculated and compared between the aspirin and fish oil cohort vs. aspirin and pulsatile stocking cohort, and aspirin and fish oil cohort vs. rivaroxaban cohort. A P value of <0.05 was used to determine statistical significance.

Results

A total of 25 DVT events were recorded including 1 of 300 (0.33%) in the aspirin and fish oil cohort, 22 of 300 (7.33%) in the aspirin and pulsatile stocking cohort and 2 of 250 (0.8%) in the rivaroxaban cohort. When comparing ORs, patients who received aspirin and fish oil demonstrated significantly lower risk for thromboembolic events when compared to the aspirin and pulsatile stocking group (OR: 0.045; 95% CI: 0.0061-0.3394; P<0.05). When compared to the rivaroxaban cohort the ORs did not differ significantly (OR: 0.416; 95% CI: 0.0376-4.6223; P>0.05). In addition, no PE events were recorded in any of the cohorts. When compared to rivaroxaban, the fish oil and aspirin cohort demonstrated significantly lower incidence of bleeding episodes (1 of 300, 0.33% vs. 30 of 250 patients, 12%; OR: 0.0278; 95% CI: 0.0038-0.2051; P<0.05). No bleeding events were recorded in the aspirin and pulsatile stocking cohort.

Conclusions

This study demonstrated the potentially synergistic anti-thromboembolic effect of aspirin and fish oil in the prevention of post-operative venous thromboembolism in primary TKA patients. Based on the results from this study, the authors conclude that the combination of aspirin and fish oil maybe an excellent thromboprophylactic modality for patients to use after TKA. These results warrant further, larger prospective studies analyzing the use of fish oil supplements in VTE prophylaxis.

Potential Underprediction of Warfarin Drug Interaction From Conventional Interaction Studies and Risk Mitigation: A Case Study With Epacadostat, an IDO1 Inhibitor

Drug-drug interaction (DDI) studies involving warfarin are typically conducted with subtherapeutic doses of warfarin to ensure the safety of volunteers. However, this approach may potentially have a systemic bias of underestimating pharmacodynamic (PD) DDI effect on warfarin at therapeutic levels of anticoagulation. We demonstrate here the utility of model-based DDI prediction for a clinically relevant warfarin regimen, using the example of epacadostat (INCB024360), the first-in-class indoleamine 2,3-dioxygenase 1 inhibitor in clinical development as a novel orally active immuno-oncological therapy. Observed data from a dedicated clinical DDI study using subtherapeutic warfarin suggested warfarin pharmacokinetics (PK), but not PD (anticoagulation), was significantly affected by concomitant epacadostat. However, subsequent PK/PD modeling and simulations indicated a clinically important DDI effect on warfarin PD at a higher baseline of the international normalization ratio (INR) and enabled recommendation of warfarin dose adjustment that is dependent on epacadostat dosing regimen and target INR.

Warfarin Dosing Algorithms Underpredict Dose Requirements in Patients Requiring ≥7 mg Daily: A Systematic Review and Meta-analysis

There is preliminary evidence to suggest that some published warfarin dosing algorithms produce biased maintenance dose predictions in patients who require higher than average doses. We conducted a meta-analysis of warfarin dosing algorithms to determine if there exists a systematic under- or overprediction of dose requirements for patients requiring ≥7 mg/day across published algorithms. Medline and Embase databases were searched up to September 2015. We quantified the proportion of over- and underpredicted doses in patients whose observed maintenance dose was ≥7 mg/day. The meta-analysis included 47 evaluations of 22 different warfarin dosing algorithms from 16 studies. The meta-analysis included data from 1,492 patients who required warfarin doses of ≥7 mg/day. All 22 algorithms were found to underpredict warfarin dosing requirements in patients who required ≥7 mg/day by an average of 2.3 mg/day with a pooled estimate of underpredicted doses of 92.3% (95% confidence interval 90.3-94.1, I² = 24%).

Clinical Pharmacokinetics and Pharmacodynamics of Lenalidomide

Lenalidomide is a lead therapeutic in multiple myeloma and deletion 5q myelodysplastic syndromes and shows promising activities in other hematologic malignancies. This article presents a comprehensive review of the clinical pharmacokinetics and pharmacodynamics of lenalidomide. Oral lenalidomide is rapidly and highly absorbed (>90 % of dose) under fasting conditions. Food affects oral absorption, reducing area under the concentration-time curve (AUC) by 20 % and maximum concentration (C max) by 50 %. The increase in AUC and C max is dose proportional, and interindividual variability in plasma exposure is low to moderate. Lenalidomide distributes into semen but is undetectable 3 days after stopping treatment. Biotransformation of lenalidomide in humans includes chiral inversion, trivial hydroxylation, and slow non-enzymatic hydrolysis. Approximately 82 % of an oral dose is excreted as lenalidomide in urine within 24 h. Lenalidomide has a short half-life (3-4 h) and does not accumulate in plasma upon repeated dosing. Its pharmacokinetics are consistent across patient populations, regardless of the type of hematologic malignancy. Renal function is the only important factor affecting lenalidomide plasma exposure. Lenalidomide has no QT prolongation risk at approved doses, and higher plasma exposure to lenalidomide is associated with increased risk of neutropenia and thrombocytopenia. Despite being a weak substrate of P-glycoprotein (P-gp) in vitro, lenalidomide does not have clinically significant pharmacokinetic interactions with P-gp substrates/inhibitors in controlled studies. The AUC-matched dose adjustment is recommended for patients with renal impairment at the start of therapy. No dose adjustment for lenalidomide is needed on the basis of age, ethnicity, mild hepatic impairment, or drug-drug interactions.

Satisfaction with and adherence to warfarin treatment: A cross-sectional study among Sudanese patients

Background

Satisfaction with and adherence to oral anticoagulant treatment are important measures that decrease morbidity and mortality. Higher satisfaction and adherence to warfarin therapy was found to be associated among other factors with good International Normalized Ratio (INR) control.

Objectives

To assess patient satisfaction with and adherence to oral anticoagulant therapy and to identify predictors of the two studied domains.

Methods

A cross-sectional study was conducted at the Cardiothoracic Clinic in Alshaab Teaching Hospital; Khartoum; Sudan during March-April 2015. A representative sample of patients on oral anticoagulant treatment was recruited. Data was collected through face-to-face interview method using oral Anti-Clot Treatment Scale (ATCS) to measure satisfaction and the 4-items Morisky Scale to measure adherence to therapy. Data was processed using SPSS. Logistic regression analysis was performed. P value <0.05 was considered statistically significant.

Results

A total of 93 patients was included, of them 46 were males. Overall, 47 (50.5%) were classified as satisfied with anti-clot treatment. Patients attained secondary and above educational level were approximately 8 times more satisfied with their anti-clot treatment, compared to those educated below this level, [OR 7.9 (2.9–21.7), P < 0.001]. Similarly, patients currently working were found to be approximately 3 times more satisfied with warfarin therapy, compared those who had no jobs, [OR 2.9 (1.1–7.6), P = 0.035]. Overall, 5.4% of the patients were found to be adherent to warfarin therapy. No definite background characteristic variable was found to be associated with adherence to treatment. No association was found between patient satisfaction and adherence to treatment, (P = 0.490).

Conclusions

Ensuring health education on warfarin together with continuous patients motivation are needed, specifically among patients with low educational level. Efficient multidisciplinary effort from all healthcare providers is needed to make warfarin treatment more successful.

Pharmacogenetic-guided Warfarin Dosing Algorithm in African-Americans

We aim to develop warfarin dosing algorithm for African-Americans. We explored demographic, clinical, and genetic data from a previously collected cohort of 163 African-American patients with a stable warfarin dose. We explored 2 approaches to develop the algorithm: multiple linear regression and artificial neural network (ANN). The clinical significance of the 2 dosing algorithms was evaluated by calculating the percentage of patients whose predicted dose of warfarin was within 20% of the actual dose. Linear regression model and ANN model predicted the ideal dose in 52% and 48% of the patients, respectively. The mean absolute error using linear regression model was estimated to be 10.8 mg compared with 10.9 mg using ANN. Linear regression and ANN models identified several predictors of warfarin dose including age, weight, CYP2C9 genotype *1/*1, VKORC1 genotype, rs12777823 genotype, rs2108622 genotype, congestive heart failure, and amiodarone use. In conclusion, we developed a warfarin dosing algorithm for African-Americans. The proposed dosing algorithm has the potential to recommend warfarin doses that are close to the appropriate doses. The use of more sophisticated ANN approach did not result in improved predictive performance of the dosing algorithm except for patients of a dose of ≥49 mg/wk.

Evaluation of pharmacokinetic and pharmacodynamic interactions when lenalidomide is co-administered with warfarin in a randomized clinical trial setting

BACKGROUND AND OBJECTIVE

Lenalidomide is an oral immunomodulatory drug used to treat multiple myeloma and some other hematological malignancies. Warfarin is often used concomitantly as prophylaxis against potential venous thromboembolism associated with lenalidomide treatment. The objective of this study was to evaluate the pharmacokinetic and pharmacodynamic drug interactions between lenalidomide and warfarin in healthy volunteers.

METHODS

This was a double-blind, placebo-controlled, randomized, two-period crossover study. Eighteen healthy male and female subjects were treated with 10 mg/day lenalidomide or placebo for 9 days. A single oral 25 mg dose of warfarin was administered on Day 4 of each treatment period. Blood was sampled to determine international normalized ratio (INR), prothrombin time (PT), and area under the plasma concentration-time curve (AUC) and maximum plasma concentration (C max) warfarin and lenalidomide.

RESULTS

The 90 % confidence intervals (CI) for the ratio of AUC or Cmax geometric means between co-administration with lenalidomide and placebo were within the 80-125 % bioequivalence bounds for R-warfarin and S-warfarin. The 90 % CI for the ratio of area under the INR curve from time zero until 144 hours after dosing (AUCINR, 0-144) or the peak INR geometric means between co-administration with lenalidomide versus placebo was also within the 85-125 % bounds. Additionally, the AUC and C max values of lenalidomide were not altered by co-administration with warfarin.

CONCLUSION

Co-administration of lenalidomide with warfarin did not alter the plasma exposure or anticoagulant effect to warfarin or the plasma exposure to lenalidomide, indicating that no dose adjustment of either drug is needed when these two drugs are co-administered.

Warfarin overdose: a 25-year experience

Warfarin, a vitamin K antagonist, is widely used for the prophylaxis and treatment of thromboembolic disease. While guidelines exist for management of a supratherapeutic international normalized ratio following therapeutic warfarin use, these guidelines are not designed for management of the acute warfarin overdose. There is a paucity of literature describing the latter. The primary objective of this manuscript is to characterize the coagulopathy and describe the bleeding events that occur after a warfarin overdose. A secondary goal is to describe the amount of vitamin K administered to patients presenting with warfarin overdoses. A retrospective chart review of patients admitted with an acute warfarin overdose at two tertiary care medical centers in the USA was conducted. Clinical characteristics were abstracted, and bleeding categories (major, minor, trivial) were defined a priori. Twenty-three patients were admitted during the time period; males accounted for 15/23 (62.5 %) subjects. The median (interquartile range (IQR)) age was 43 (32-48.5) years. Seventeen subjects received vitamin K, with a median (IQR) dose of 15 (10-50) mg. The maximal total amount of vitamin K administered to a single patient during the index hospitalization was 110 mg. Three bleeding events occurred; one classified as major, and two as minor. All patients made a full recovery. In this case series of acute warfarin overdose, nearly all patients developed a coagulopathy, and nearly three-quarters of patients received vitamin K. Bleeding events occurred in a minority of patients.

A review of a priori regression models for warfarin maintenance dose prediction

A number of a priori warfarin dosing algorithms, derived using linear regression methods, have been proposed. Although these dosing algorithms may have been validated using patients derived from the same centre, rarely have they been validated using a patient cohort recruited from another centre. In order to undertake external validation, two cohorts were utilised. One cohort formed by patients from a prospective trial and the second formed by patients in the control arm of the EU-PACT trial. Of these, 641 patients were identified as having attained stable dosing and formed the dataset used for validation. Predicted maintenance doses from six criterion fulfilling regression models were then compared to individual patient stable warfarin dose. Predictive ability was assessed with reference to several statistics including the R-square and mean absolute error. The six regression models explained different amounts of variability in the stable maintenance warfarin dose requirements of the patients in the two validation cohorts; adjusted R-squared values ranged from 24.2% to 68.6%. An overview of the summary statistics demonstrated that no one dosing algorithm could be considered optimal. The larger validation cohort from the prospective trial produced more consistent statistics across the six dosing algorithms. The study found that all the regression models performed worse in the validation cohort when compared to the derivation cohort. Further, there was little difference between regression models that contained pharmacogenetic coefficients and algorithms containing just non-pharmacogenetic coefficients. The inconsistency of results between the validation cohorts suggests that unaccounted population specific factors cause variability in dosing algorithm performance. Better methods for dosing that take into account inter- and intra-individual variability, at the initiation and maintenance phases of warfarin treatment, are needed.

A Proposal for an Individualized Pharmacogenetic-Guided Warfarin Dosage Regimen for Puerto Rican Patients Commencing Anticoagulation Therapy

Warfarin is the current standard of care in oral anticoagulation therapy. It is commonly prescribed to treat venous thromboembolism, pulmonary embolism, acute myocardial infarction, and to decrease the risk of stroke in atrial fibrillation. Warfarin therapy is challenging because of marked and often unpredictable inter-individual dosing variations that effectively reach and maintain adequate anticoagulation. Several researchers have developed pharmacogenetic-guided maintenance dose algorithms that incorporate genetics and individual patient characteristics. However, there is limited information available concerning dosing during warfarin initiation. This is considered the most clinically challenging therapeutic phase. In such, the risk of recurrent thromboembolism and hemorrhage are elevated. The objective of this retrospective study is to predict the individual initial doses for Puerto Rican patients (n=175) commencing anticoagulation therapy at Veterans Affairs Caribbean Healthcare System (VACHS) using pharmacogenetic/pharmacokinetic-driven model. A pharmacogenetic driven model (R2=0.4809) was developed in Puerto Rican patients and combined with pharmacokinetic formulas that enabled us to predict the individual initial doses for patients (n=121) commencing anticoagulation therapy. WinNonlin® pharmacokinetic-pharmacodynamic simulations were carried out to determine the predictability of this model. This model demonstrated promising results with few (n=10) simulations outside of their respective therapy range. A customized pharmacogenetic-based warfarin maintenance dose algorithm (R2=0.7659) was developed in a derivation cohort of 131 patients. The predictability of this developed pharmacogenetic algorithm was compared with the International Warfarin Pharmacogenomics Consortium (IWPC) algorithm and it demonstrated superior predictability within our study population.

Managing anticoagulation for atrial fibrillation: current issues and future strategies

Although warfarin is superior to aspirin in reducing the risk of stroke in patients with atrial fibrillation, it can increase major bleeds. Hence, physicians stratify patients according to stroke risk to ensure a net benefit. In this review, the CHA(2) DS(2) -VASc stratification scheme used in the latest European Society of Cardiology (2010/12) guidelines will be explained. The greater sensitivity of this scheme, compared to the previous CHADS(2) , more closely delineates patients for whom warfarin is appropriate. The review also anticipates that there will be a wider range of patients who may benefit from the new oral anticoagulants, which show similar or superior efficacy and/or safety to warfarin with a significant reduction in intracranial haemorrhage and do not require routine coagulation monitoring. The role of conventional and new anticoagulant options will also be discussed.

The effectiveness and safety of fixed low-dose prothrombin complex concentrates in patients requiring urgent reversal of warfarin

BACKGROUND

A rapid method of reversal is required for patients on warfarin who suffer acute bleeding or require emergency surgery. Prothrombin complex concentrates (PCCs) have recently been recommended by the Canadian Blood Services for use at a fixed low dose of 1000 IU of Factor (F)IX activity. The main goal of this study was to investigate both the effectiveness and the safety of fixed low-dose PCCs.

STUDY DESIGN AND METHODS

We retrospectively reviewed charts from 103 patients who received PCCs for reversal of warfarin therapy.

RESULTS

A total of 103 patients were treated with PCC at a single fixed dose of 1000 IU of F IX activity. Fifty patients (48.5%) had a final international normalized ratio (INR) response of not more than 1.5 and an additional 45 patients (43.7%) had a final INR response between 1.6 and 2.0. However, 86 patients (83.5%) had an excellent clinical response consisting of control of bleeding without the requirement of additional measures. In a multivariable model, patients who received fresh-frozen plasma and patients who were given doses greater than 1000 IU of PCC were both identified as predictors of a poor clinical response (odds ratio [OR] 3.48, 95% confidence interval [CI] 0.76-15.89, p = 0.11; and OR 10.8, 95% CI 2.08-56.28, 95% CI, p = 0.005, respectively). There were five adverse events up to 30 days after PCC use.

CONCLUSION

At a fixed dose of 1000 IU of F IX activity, PCC seems to be effective and safe but randomized controlled trials, specifically examining different doses of PCC, are required to confirm the above observations.

Emergency management of bleeding associated with old and new oral anticoagulants

As major prescribers of oral anticoagulants, cardiologists must be familiar with strategies to manage bleeding, the principal complication associated with all anticoagulants, and to reverse anticoagulant effects in acute-care settings. The purpose of this manuscript is to review currently available information regarding dabigatran and rivaroxaban, the 2 novel oral anticoagulants approved to date in the United States. Further, we suggest reasonable interventions for the clinician faced with a patient who suffers a major bleeding event while receiving one of these agents. Data sources were peer-reviewed publications, US Food and Drug Administration documents in the public domain, and approved US prescribing information for dabigatran (Pradaxa) and rivaroxaban (Xarelto). Strategies for management of bleeding and reversal of anticoagulant effects from warfarin include vitamin K, fresh frozen plasma, and prothrombin complex concentrates. For rivaroxaban and dabigatran, appropriate therapies include support and observation, which are likely to be effective for the majority of patients because of the short half-lives of these agents. In severe life-threatening hemorrhage, clotting-factor substitutes may be appropriate in certain situations. Validated protocols specific to each agent remain to be developed.

Factors affecting medication adherence and anticoagulation control in Korean patients taking warfarin

BACKGROUND AND RESEARCH OBJECTIVE

Poor adherence in patients taking warfarin may be one of the most common barriers to obtain favorable anticoagulation outcomes. This study was conducted to identify factors affecting medication adherence and their relationships with anticoagulation control in Korean patients taking warfarin.

SUBJECTS AND METHODS

In a cross-sectional survey, 204 patients taking warfarin who had visited an outpatient clinic of a cardiovascular center located in Seoul, Korea, were included as research subjects. Medication adherence, knowledge about warfarin, self-efficacy, and patient understanding of the international normalized ratio (INR) were investigated. Participants' medical records were also reviewed to identify clinical characteristics including comorbid conditions, warfarin regimen, and INR.

RESULTS AND CONCLUSIONS

When medication adherence was defined as taking warfarin according to medical advice (frequency, dosage, time, and precautions), 56 (27.5%) of 204 respondents were adherent. The adherent group had a greater understanding about warfarin than the nonadherent group as measured by 10 survey items (7.20 ± 1.70 vs 6.56 ± 1.84; P < .05) and had significantly higher self-efficacy (P < .000). However, medication adherence was not associated with good anticoagulation level as measured by INR. The results show that knowledge about warfarin and self-efficacy exert significant influence on medication adherence, and yet medication adherence did not predict therapeutic anticoagulation control. Further studies are needed to identify factors predicting favorable anticoagulation control in patients taking warfarin.

Warfarin therapeutic monitoring: is 70% time in the therapeutic range the best we can do?

WHAT IS KNOWN AND OBJECTIVE

Warfarin, an oral anticoagulant, which has been in clinical use for over sixty years, remains a challenge for clinicians to utilize, given the multiplicity of items which can limit its efficacy. Our objective is to review the evidence and comment on whether INR control can be better than has been currently reported in various studies.

COMMENT

The duration of time a patient's international normalized ratio (INR) is maintained within the therapeutic range (time in the therapeutic range, TTR) for his or her particular indication for the drug impacts the effectiveness and safety of warfarin therapy. Maintaining a therapeutic INR while on warfarin is difficult, and numerous studies employing various strategies confirm the challenge, but not the impossibility of achieving a TTR above 70%.

WHAT IS NEW AND CONCLUSION

Maintaining a therapeutic INR requires a dedicated multi-faceted approach. With diligence, skill and various therapeutic strategies, a TTR >70% can be achieved.