Oral anticoagulants: mechanism of action, clinical effectiveness, and optimal therapeutic range

Characterization of ADME Gene Variation in Colombian Population by Exome Sequencing

In genes related to drug pharmacokinetics, molecular variations determine interindividual variability in the therapeutic efficacy and adverse drug reactions. The assessment of single-nucleotide variants (SNVs) is used with growing frequency in pharmacogenetic practice, and recently, high-throughput genomic analyses obtained through next-generation sequencing (NGS) have been recognized as powerful tools to identify common, rare and novel variants. These genetic profiles remain underexplored in Latin-American populations, including Colombia. In this study, we investigated the variability of 35 genes included in the ADME core panel (absorption, distribution, metabolism, and excretion) by whole-exome sequencing (WES) of 509 unrelated Colombian individuals with no previous reports of adverse drug reactions. Rare variants were filtered according to the minor allele frequencies (MAF) <1% and potential deleterious consequences. The functional impact of novel and rare missense variants was assessed using an optimized framework for pharmacogenetic variants. Bioinformatic analyses included the identification of clinically validated variants described in PharmGKB and ClinVar databases. Ancestry from WES data was inferred using the R package EthSEQ v2.1.4. Allelic frequencies were compared to other populations reported in the public gnomAD database. Our analysis revealed that rare missense pharmacogenetic variants were 2.1 times more frequent than common variants with 121 variants predicted as potentially deleterious. Rare loss of function (LoF) variants were identified in 65.7% of evaluated genes. Regarding variants with clinical pharmacogenetic effect, our study revealed 89 sequence variations in 28 genes represented by missense (62%), synonymous (22.5%), splice site (11.2%), and indels (3.4%). In this group, ABCB1, ABCC2, CY2B6, CYP2D6, DPYD, NAT2, SLC22A1, and UGTB2B7, are the most polymorphic genes. NAT2, CYP2B6 and DPYD metabolizer phenotypes demonstrated the highest variability. Ancestry analysis indicated admixture in 73% of the population. Allelic frequencies exhibit significant differences with other Latin-American populations, highlighting the importance of pharmacogenomic studies in populations of different ethnicities. Altogether, our data revealed that rare variants are an important source of variability in pharmacogenes involved in the pharmacokinetics of drugs and likely account for the unexplained interindividual variability in drug response. These findings provide evidence of the utility of WES for pharmacogenomic testing and into clinical practice.

Development of a Fluorescent Microfluidic Device Based on Antibody Microarray Read-Out for Therapeutic Drug Monitoring of Acenocoumarol

The development of a proof-of-concept point-of-care (PoC) device for the determination of oral anticoagulants determination is presented. Acenocoumarol (ACL) is prescribed to prevent certain cardiovascular diseases related to the prevention of deep vein thrombosis, pulmonary embolism, myocardial infarction, and stroke. Oral anticoagualant treatment (OAT) represents a population of 2% under treatment which has expenditures about $ 144 million in 2011. The main drawback for OAT is the associated narrow therapeutic window and the unpredictable dose-response relationship, which is one of the main causes for visiting the emergency room at the hospitals. In a previous work, family antibodies were produced for the simultaneous detection of ACL and warfarin (W) depending on the area of application. It was developed in different formats, indirect and direct, either with similar detectabilities and both assays quantifying the oral anticoagulants with high accuracy and reproducibility. We present the implementation of the already developed immunochemical method to a point-of-care (PoC) device to assist on the patient compliance assessment programs. In order to achieve this goal, a first development was performed implementing ACL ELISA assay into a microarray format with fluorescent read-out. The assay was successfully implemented achieving a LOD of 1.23 nM of ACL directly measured in human plasma. Then, a fully integrated microfluidic system is developed which incorporates the specific immunoreagents for the detection of ACL. The immunoreagents were attached onto the glass slide in a microarray format. The system is automatic, rapid, sensitive, and disposable that could help clinicians monitor patients under OAT. According to the fluorescent label of the ACL binding, the chip can be easily read with a scanner. The microfluidic system performed good according to the robust and reproducible signals, and subsequently yielded an accurate result.

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.

Evaluation of an Initiation Regimen of Warfarin for International Normalized Ratio Target 2.0 to 3.0

Background: he number of patients on warfarin therapy is rising steadily. Although warfarin is beneficial, it carries a high risk of bleeding, especially if the international normalized ratio (INR) values exceed 3.0. Currently, no warfarin initiation regimens have been developed for the Asian population, especially for Malaysians. Objective: This article describes the efficacy and safety of a new initiation regimen for warfarin among warfarin-naive patients. Method: Data were retrospectively collected from the ambulatory and inpatient settings. Results: A total of 165 patients who each had a target INR of 2.0 to 3.0 were included in the study. The mean age was 57.2 years and 94 patients were male. A total of 108 patients used Regimen 1 (5 mg/5 mg/3mg) and the rest of the patients used Regimen 2 (5 mg/3 mg/3 mg). Most patients used warfarin either for atrial fibrillation (52.1%) or for venous thromboembolism (29.7%). Overall, 88 of the patients had INR values above 50% from the baseline on Day 4. Additionally, 13 patients had INR values of >3.2, which required withholding and lower dose of warfarin. The predicted weekly maintenance warfarin dose (23 ± 0.5 mg/week) was found to have correlated closely with the actual maintenance dose (22.8 ± 0.5 mg/week; r ² = 0.75). Nearly two thirds (70.3%) of the patients achieved the target INR on Day 11. Conclusion: The warfarin initiation regimens in this study was simple, safe, and suitable to be used in both ambulatory and inpatient settings for managing warfarin therapy.

Interaction Between Chinese Medicine and Warfarin: Clinical and Research Update

Background: Warfarin is a commonly used oral anticoagulant. It has a narrow therapeutic window and wide variation in individualized dosing, and is used clinically for the treatment of thromboembolic diseases. Due to the widespread use of traditional Chinese medicine (TCM) in China and the complex composition and diverse mechanisms of action of TCM, the combination of TCM and warfarin in patients has led to fluctuations in the international normalized ratio of warfarin or bleeding. To ensure rational clinical use, we summarize the TCMs with which warfarin interacts and the possible mechanisms, with a view to providing a clinical reference. Aim of the study: To summarize the mechanisms by which Chinese herbal medicines affect the enhancement or weakening of the anticoagulant effect of warfarin, to provide theoretical references for clinicians and pharmacists to use warfarin safely and rationally, and to avoid the adverse effects associated with the combination of Chinese herbal medicines and warfarin. Methods: A computerized literature search of electronic databases, including PubMed, MEDLINE, Cochrane Library, Web of Science (WOS), China National Knowledge Infrastructure (CNKI) and WANFANG Data was performed. Key words used in the literature search were "warfarin", "Chinese medicine", "traditional Chinese medicine", "Chinese patent medicine" etc. and their combinations in a time limit from January 1, 1990 to May 1, 2021. A total of 64 articles were obtained following the selection process, including clinical reports, pharmacological experiments and in vitro experiments which were reviewed to determine the mechanism of the anticoagulant effect of herbal medicine on warfarin. Results: The mechanisms affecting the anticoagulant effect of warfarin are complex, and herbal medicines may enhance and diminish the anticoagulant effect of warfarin through a variety of mechanisms; thus, clinical use needs to be cautious. Some herbal medicines have shown inconsistent results in both in vivo and ex vivo experiments, pharmacology and clinical studies, and should be the focus of future research. Conclusion: With the widespread use of TCM, the combination of warfarin and TCM is more common. This article will promote clinicians' knowledge and understanding of the TCMs which interact with warfarin, in order to avoid the occurrence of adverse clinical treatment processes, and improve the efficacy and safety.

Antithrombotic and Antiplatelet Drug Toxicity

Anticoagulant and antiplatelet drugs target a specific portion of the coagulation cascade or the platelet activation and aggregation pathway. The primary toxicity associated with these agents is hemorrhage. Understanding the pharmacology of these drugs allows the treating clinician to choose the correct antidotal therapy. Reversal agents exist for some of these drugs; however, not all have proven patient-centered outcomes. The anticoagulants covered in this review are vitamin K antagonists, heparins, fondaparinux, hirudin derivatives, argatroban, oral factor Xa antagonists, and dabigatran. The antiplatelet agents reviewed are aspirin, adenosine diphosphate antagonists, dipyridamole, and glycoprotein IIb/IIIa antagonists. Additional notable toxicities are also reviewed.

Development of a system to support warfarin dose decisions using deep neural networks

The first aim of this study was to develop a prothrombin time international normalized ratio (PT INR) prediction model. The second aim was to develop a warfarin maintenance dose decision support system as a precise warfarin dosing platform. Data of 19,719 inpatients from three institutions was analyzed. The PT INR prediction algorithm included dense and recurrent neural networks, and was designed to predict the 5th-day PT INR from data of days 1-4. Data from patients in one hospital (n = 22,314) was used to train the algorithm which was tested with the datasets from the other two hospitals (n = 12,673). The performance of 5th-day PT INR prediction was compared with 2000 predictions made by 10 expert physicians. A generator of individualized warfarin dose-PT INR tables which simulated the repeated administration of varying doses of warfarin was developed based on the prediction model. The algorithm outperformed humans with accuracy terms of within ± 0.3 of the actual value (machine learning algorithm: 10,650/12,673 cases (84.0%), expert physicians: 1647/2000 cases (81.9%), P = 0.014). In the individualized warfarin dose-PT INR tables generated by the algorithm, the 8th-day PT INR predictions were within 0.3 of actual value in 450/842 cases (53.4%). An artificial intelligence-based warfarin dosing algorithm using a recurrent neural network outperformed expert physicians in predicting future PT INRs. An individualized warfarin dose-PT INR table generator which was constructed based on this algorithm was acceptable.

Warfarin dose adjustment required after cannabidiol initiation and titration

PURPOSE

A case of a possible interaction between cannabidiol and warfarin is presented along with a brief overview of cytochrome enzymes involved in these drugs' metabolism.

SUMMARY

A 46-year-old male taking warfarin for treatment of a deep venous thrombosis was initiated on a Food and Drug Administration (FDA)-approved cannabidiol product (Epidiolex, Greenwich Biosciences) for intractable epilepsy. The patient's International Normalized Ratio (INR) was monitored closely during cannabidiol initiation and dose titration. The patient required a nearly 20% warfarin dose reduction to maintain an INR within the goal range after starting therapy with cannabidiol. There is 1 other case report describing a clinically significant interaction between cannabidiol (specifically Epidiolex) and warfarin in a patient receiving warfarin who was enrolled in a study involving the initiation and titration of cannabidiol; that patient developed a supratherapeutic INR of 6.86 and required a 30% reduction in the weekly warfarin dose to reachieve the goal INR.

CONCLUSION

A previously published report suggesting an interaction between cannabidiol and warfarin is supported by this case report. INR should be monitored frequently in patients taking warfarin who begin to take FDA-approved cannabidiol. Additional studies should be performed to clarify the interaction potential of cannabidiol and warfarin.

Impact of Interferons and Biological Drug Inhibitors of IL-2 and IL-6 on Small-Molecule Drug Metabolism Through the Cytochrome P450 System

OBJECTIVE

Assess the impact of interferons and interleukin (IL)-2 and IL-6 inhibitors on cytochrome P450 (CYP) drug metabolism in human subjects.

DATA SOURCES

PubMed search from 1980 to March 31, 2021, limited to human subjects and English language via search strategy: (biological drug names) [AND] (cytochrome [OR] CYP metabolism).

STUDY SELECTION AND DATA EXTRACTION

Narrative review of human studies assessing biological drugs in select classes that affect CYP drug metabolism.

DATA SYNTHESIS

Exogenous interferons suppress CYP1A2 (theophylline, caffeine, antipyrone) clearance by 20% to 49% in patients; have minimal impact on CYP3A4 (midazolam and dapsone), CYP2C9 (tolbutamide), or CYP2C19 (mephenytoin) metabolism; and increase CYP2D6 (debrisoquine, dextromethorphan) metabolism. Biological IL-2 inhibitors (basiliximab, daclizumab) have no effect on metabolism via CYP1A2 (caffeine), CYP2C9 (s-warfarin), CYP2C19 (omeprazole), CYP2D6 (dextromethorphan), and CYP3A4 (midazolam, tacrolimus) but may enhance CYP3A4 (cyclosporin) metabolism over time. IL-6 inhibitors (sirukumab, tocilizumab, sarilumab) significantly enhance metabolism via CYP2C9 (s-warfarin), CYP2C19 (omeprazole), and CYP3A4 (simvastatin, midazolam) and reduce metabolism via CYP1A2 (caffeine).

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Patients using interferons, IL-2, or IL-6 blocking drugs at steady state with CYP substrates could have altered drug metabolism and experience adverse events. With interferons and biological anti-inflammatory drugs, some isoenzymes will be inhibited, whereas others will be enhanced, and the magnitude of the effect can sometimes be significant. In clinical practice, clinicians may consider these metabolic changes as an additive effect to a patient's entire disease and medication profile when determining risk/benefit of treatment.

CONCLUSIONS

Interferon therapy or inflammatory suppression via IL-2 or IL-6 can alter steady-state concentrations of CYP-metabolized small-molecule drugs.

Incidence Rates of Bleeding and Emergency Surgery Due to Trauma or Fracture Among Japanese Patients with Non-valvular Atrial Fibrillation Receiving Oral Anticoagulation Therapy

Introduction

In patients with nonvalvular atrial fibrillation (NVAF) receiving oral anticoagulants (OACs), reversal of coagulopathy can be achieved with specific reversal drugs such as idarucizumab, which is indicated for use in patients treated with dabigatran for cases of life-threatening or uncontrolled bleeding or during emergency procedures that may cause serious bleeding. This study examined the incidence rate (IR) of emergency surgeries and major bleeding episodes associated with fractures and trauma in Japanese patients with NVAF receiving OACs.

Methods

This retrospective, non-interventional analysis of health insurance claims was conducted using data from 62,888 OAC-naive adult patients with NVAF who initiated dabigatran, warfarin, apixaban, rivaroxaban, or edoxaban between March 2011 and June 2016. The primary endpoint was overall IR of emergency surgery or major bleeding due to fracture or trauma.

Results

Overall IR of emergency surgery or major bleeding due to fracture or trauma considering outcomes until OAC discontinuation was 0.489 per 100 patient-years (PY) (95% confidence interval [CI] 0.406–0.572). Considering first OAC exposure only, the IR was 0.483 per 100 PY (95% CI 0.394–0.573). Emergency surgery/major bleeding events due to fracture or trauma was highest in those aged ≥ 75 years (0.611 per 100 PY [95% CI 0.481–0.741]).

Conclusions

Fewer than one in 200 patients per year with NVAF receiving OACs experience emergency surgeries and major bleeding episodes associated with fractures and trauma; however, the IR of these events is markedly higher in patients of advanced age.

Trial registration

ClinicalTrials.gov 207, NCT03254147.

Patients with an abnormal heart rhythm (nonvalvular atrial fibrillation [NVAF]) have a higher risk of blood clots and stroke (which is when the blood supply to part of the brain is blocked). To reduce these risks, patients can take anticoagulants that slow or prevent the formation of blood clots. However, if the patient needs major emergency surgery or has a severe injury, the anticoagulants can increase their risk of bleeding, which can sometimes be life-threatening. There are drugs (e.g., idarucizumab) that can be used to reverse the effects of anticoagulants in this type of emergency. What we don’t know is how many NVAF patients in Japan who are on anticoagulants have emergency surgeries or major bleeding after an injury, and therefore may require a reversal drug. The authors looked at Japanese health insurance claim data from 62,888 adult patients with NVAF who started taking an anticoagulant. They found that, annually, approximately 0.5% of the patients had emergency surgery or a major bleed associated with a fracture or injury. In very elderly patients (aged at least 75 years), the annual percentage was approximately 0.6%, which was almost double the annual percentage in patients aged less than 65 years. The authors concluded that, even though the number of people requiring a reversal agent are quite small, it is important to have an effective reversal agent for patients on anticoagulants, particularly older patients.

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.

Review of Therapeutic Options for the Prevention of VTE in Total Joint Arthroplasty

Hip and knee arthroplasty patients are at high risk of perioperative venous thromboembolic events (VTE). VTE has been well studied in this population and it is recommended that total joint arthroplasty recipients receive chemoprophylactic anticoagulation due to risk factors inherent to the surgical intervention. There are few concise resources for the orthopedic surgeon that summarize data regarding post-operative anticoagulation in the context of currently available therapeutic options and perioperative standards of practice. The periodic reexamination of literature is essential as conclusions drawn from studies predating perioperative protocols that include early mobilization and sequential compression devices as standards of practice in total joint arthroplasty are no longer generalizable to modern-day practice. We reviewed a large number of recently published research studies related to post-operative anticoagulation in total joint arthroplasty populations that received a high Level of Evidence grade. Current literature supports the use of oral aspirin regimens in place of more aggressive anticoagulants, particularly among low risk patients. Oral aspirin regimens appear to have the additional benefit of lower rates of bleeding and wound complications. Less consensus exists among high risk patients and more potent anticoagulants may be indicated. However, available evidence does not demonstrate clear superiority among current options, all of which may place patients at a higher risk of bleeding and wound complications. In this situation, chemoprophylactic selection should reflect specific patient needs and characteristics.

Platelet-Based Drug Delivery for Cancer Applications

Platelets can be considered as the "guardian of hemostasis" where their main function is to maintain vascular integrity. In pathological conditions, the hemostatic role of platelets may be hijacked to stimulate disease progression. In 1865, Armand Trousseau was a pioneer in establishing the platelet-cancer metastasis relationship, which he eventually termed as Trousseau's Syndrome to describe the deregulation of the hemostasis-associated pathways induced by cancer progression (Varki, Blood. 110(6):1723-9, 2007). Since these early studies, there has been an increase in experimental evidence not only to elucidate the role of platelets in cancer metastasis but also to create novel cancer therapies by targeting the platelet's impact in metastasis. In this chapter, we discuss the contribution of platelets in facilitating tumor cell transit from the primary tumor to distant metastatic sites as well as novel cancer therapies based on platelet interactions.

Improving warfarin therapy through implementation of a hospital-based pharmacist managed clinic in Jamaica

Background

Pharmacist managed warfarin clinics can improve the anticoagulation status of non-valvular patients. The first of such services was implemented at the Cornwall Regional Hospital in Jamaica in 2013.

Objectives

To assess the anticoagulation control of patients on warfarin therapy over six months in the pharmacist managed warfarin clinic at Cornwall Regional Hospital.

Methods

Retrospective docket review for the period January 2014 to December 2016 was done to include data of patients attending routine clinic appointments for at least six months. Age, gender, date of visit, indication for warfarin therapy, warfarin dose and International Normalized Ratio readings were extracted. Percentage time spent in therapeutic range (TTR) was calculated by month for six months using the Rosendaal linear interpolation method. Patient anticoagulation status was categorized as poor (TTR<40%), moderate (TTR=40-64%) or good (TTR≥65%) and anticoagulation status at three months and six months was compared.

Results

For the period of assessment, 52 patients were identified; the median age was 58 years and 36 patients were males. Deep vein thrombosis was the main indication for therapy (22 of 52) and median warfarin weekly dose ranged was 15.0-130 mg. At time of recruitment most of the patients were outside the target INR range (43 of 52). Within one month, the median TTR attained was 31% [IQR 62-10]. This significantly improved by second month to 60% [IQR 82-23] (p=0.001). By month three, the proportion of patients in good, moderate and poor anticoagulant status was 19/51, 15/51 and 17/51 respectively, which at six months changed to 23/51, 12/51. 16/51 respectively; thus, although coagulation status improved from month one to three, there was no significant improvement from month three to month six (p=0.31).

Conclusions

The pharmacist managed warfarin clinic monitoring services were successful in attaining TTRs >40% and sustaining these values over six months. The services should therefore be encouraged.

Effects of coagulation factor VII polymorphisms on warfarin sensitivity and responsiveness in Jordanian cardiovascular patients during the initiation and maintenance phases of warfarin therapy

Purpose

This study aims to investigate the relationships between genetic polymorphisms of the coagulation factor VII (FVII) gene and warfarin responsiveness and sensitivity.

Patients and methods

The study population consisted of 417 subjects (207 Jordanian cardiovascular patients and 210 healthy individuals). Cardiovascular patients were classified into two groups: those sensitive to warfarin dosage (sensitive, moderate, and resistant) and those responsive to warfarin based on International Normalized Ratios (INRs; poor, good, and extensive responders). The HVR4 polymorphism of the FVII gene was genotyped.

Results

Our results showed that there are significant differences between patients and controls according to both genotypic and allelic frequencies (P<0.0001) in the genetic susceptibility study. Moreover, the pharmacogenetics study reported that HVR4 had no association with warfarin sensitivity or responsiveness during the initiation and maintenance phases of therapy, the only significant differences were in the INR outcome measured during the maintenance phase of therapy (P=0.012).

Conclusion

Our data suggests lacking of association between the HVR4 polymorphism in the FVII gene and warfarin sensitivity and responsiveness during the initiation and maintenance phases of therapy. It is possible that these patients carry additional mutations in genes involved in the coagulation pathway.

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.

Pharmacokinetics of new oral anticoagulants: implications for use in routine care

INTRODUCTION

Since 2008, new oral anticoagulants (NOACs) have been approved for the prevention of venous thromboembolism (VTE) in patients receiving hip or knee replacement surgery, prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation (NVAF), treatment of deep vein thrombosis (DVT), and pulmonary embolism (PE). Premarketing randomized clinical trials (RCTs) of NOACs demonstrated their non-inferiority in terms of efficacy vs. warfarin (traditional oral anticoagulant - TOA), with lower risk of serious adverse drug reactions, especially cerebral hemorrhages. In clinical practice, pharmacokinetic aspects of NOACs have to be carefully taken into account to optimize the benefit-risk profile of these drugs. Areas covered: An overview of major issues related to pharmacokinetics of NOACs, such as drug-drug interactions, over- and underdosage in special populations (e.g. elderly, underweight, and chronic kidney disease patients), and impact on adherence and persistence to NOACs therapy and ultimately clinical outcomes in real-world setting, is provided. Expert opinion: NOACs have been proven to be a better option than traditional anticoagulants due to better tolerability and ease of use. However, given specific pharmacokinetic characteristics, NOAC therapy has to be carefully tailored and monitored in relation to patient characteristics with the final goal of maximizing benefits and minimizing risks.

Phenotyping of CYP 4501A2 Activity by Total Overnight Salivary Caffeine Assessment (TOSCA) in Patients on Warfarin Treatment: A Cross-Sectional Study

Warfarin is an oral anticoagulant, commonly used for primary and secondary prevention of venous and arterial thromboembolic events. The drug is characterized by narrow therapeutic index, widespread individual variability in clinical response, and high rates of adverse events, particularly bleeding complications. For these reasons, a close monitoring of the dosage, using the frequent assessment of coagulation status by means of International Normalized Ratio value, is mandatory. Warfarin is metabolized by hepatic cytochrome P-450. High CYP 450 activity may lead to low drug concentration and requires high warfarin doses to reach efficacy; conversely, low CYP 450 activity is responsible for high drug concentration and needs for low doses to avoid potential toxicity risks. The major isoforms of CYP involved in the metabolism of warfarin sodium are CYP1A2 (for the R-warfarin) and CYP2C9 (for the S-warfarin). The probes for testing CYP1A2 are phenacetin and caffeine while for CYP2C9 tolbutamide. Although S-warfarin has major activity, it was decided to exclude its phenotyping for ethical issues, being mandatory to use a drug (tolbutamide). Instead, it was chosen to test the 1A2 isoform, as the activity of the latter isoform could be investigated by using caffeine contained in the caffeinated beverages. Specifically, a single-point concentration of salivary caffeine (total overnight salivary caffeine assessment [TOSCA]) after an overnight period of the caffeinated beverages abstinence was utilized. In the present study, 75 nonsmoker patients regularly receiving warfarin sodium were enrolled. The results have showed a significant association of the warfarin dose with TOSCA values (coefficient = -0.15, standard error = 0.04, 95% confidence interval = -0.24 to -0.06, t = -3.23, P = .002). In conclusion, the phenotyping of CYP1A2 by TOSCA could be useful, if further proven, to help manage patients on warfarin in order to lessen severe adverse events.

Evaluation of anticoagulant agents for the treatment of human metapneumovirus infection in mice

Thrombin has been demonstrated to be involved in several viral diseases including human metapneumovirus (hMPV) infections. We previously showed that immediate administration of thrombin inhibitor argatroban post-infection protected mice against hMPV disease. This current work aims at determining whether warfarin and heparin, two other anticoagulants inhibiting thrombin formation and activities, may also be used for treatment against hMPV in vivo. We found that immediate injections of argatroban, warfarin or heparin after virus challenge protected mice against hMPV infection, as evidenced by decreased or no mortality, less weight loss, reduced viral load and attenuated inflammation. However, delayed treatments starting 1 day post-infection with argatroban or warfarin almost did not impact the survival whereas delayed treatment with heparin induced an increased mortality during infection. Moreover, these treatments also did not reduce weight loss, viral replication and inflammation. In agreement with these results, thrombin generation was decreased upon immediate anticoagulant treatments but was unaltered upon delayed treatments. Thus, thrombin generation occurs at the onset of hMPV infection and thrombin inhibition may be only useful for the treatment of this disease when initiated in the early stage. In this case, heparin is not recommended because of its reduced efficacy on mortality in infected mice whereas argatroban and warfarin appear as safe and effective drugs for the treatment of hMPV disease. The antiviral and anti-inflammatory effects of argatroban occur via thrombin-dependent pathways whereas the mechanisms by which warfarin exerts its beneficial effects against hMPV infection were not elucidated and need to be further studied.

Bleeding in patients who underwent scheduled second-look endoscopy 5 days after endoscopic submucosal dissection for gastric lesions

Background

Bleeding after endoscopic submucosal dissection (ESD) in antithrombotic drug users is still one of the important issues to be solved. We performed scheduled second-look endoscopy (SLE) 5 days after ESD, when the resumption of antithrombotic agents is assumed to have achieved a steady state, rather than on the day after ESD. We investigated bleeding incidence and the status of ulcers.

Methods

A total of 299 lesions in 299 patients subjected to ESD for gastric neoplasms were enrolled. A double dose of proton pump inhibitors was administered after ESD. SLE was planned 5 days after ESD. Post-ESD bleeding occurring before SLE was defined as early phase post-ESD bleeding, whereas bleeding after SLE was defined as later phase post-ESD bleeding. Forrest IIa and IIb ulcers are defined as high-risk ulcers requiring prophylactic hemostasis. We investigated risk factors for post-ESD bleeding, particularly focusing on the use of antithrombotic agents and the presence of high-risk ulcers requiring prophylactic hemostasis during SLE.

Results

Under a double dose of proton pump inhibitors, early phase post-ESD bleeding occurred in 2.3% of non-users (5/218) and 6.2% of users of antithrombotic agents (5/81). High-risk ulcers were found in 19.0% of the cases during scheduled SLE (55/289). Later phase bleeding occurred in 5.5% of cases [2.8% of non-users (6/213) and 13.2% of users of antithrombotic agents (10/76)]. Cox regression analysis revealed that the risk factor for post-ESD bleeding was antithrombotic treatment (HR: 3.56; 95% CI: 1.63–8.02, p = 0.002) alone. Among patients with high-risk ulcers, a statistically significant increase in bleeding was observed in the later phase in patients under antithrombotic therapy, compared to those not receiving any antithrombotic agents (p = 0.001).

Conclusions

Antithrombotic treatment is a risk factor for post-ESD bleeding despite SLE being scheduled 5 days after ESD. Later phase post-ESD bleeding was observed in 13.2% of the patients under antithrombotic treatment even after prophylactic hemostasis for high-risk ulcers.

Trial registration

This study was registered in the UMIN Clinical Trials Registry System (000023306). Retrospectively registered on 23rd July 2016.

microRNAs in the haemostatic system: More than witnesses of thromboembolic diseases?

MicroRNAs (miRNAs) are small endogenous RNAs that post-transcriptionally regulate gene expression. In the last few years, these molecules have been implicated in the regulation of haemostasis, and an increasing number of studies have investigated their relationship with the development of thrombosis. In this review, we discuss the latest developments regarding the role of miRNAs in the regulation of platelet function and secondary haemostasis. We also discuss the genetic and environmental factors that regulate miRNAs. Finally, we address the potential use of miRNAs as prognostic and diagnostic tools in thrombosis.

Clinical verification of Lou type warfarin pharmacokinetic dosing algorithms equation

Warfarin is the most commonly used oral anti-coagulant in clinic practice. However, it is difficult to recommend the correct dosage due to its narrow therapeutic window. The aim of the present study was to verify the clinical value of the Lou type equation, using pharmacogenetics‑based warfarin dosing algorithms to appropriately predict the actual maintenance dose. A total of 87 Chinese Han patients who required treatment with warfarin were enrolled and randomly divided into the experimental and control groups. In the experimental group, the first 3 doses of warfarin were calculated according to the Lou type equation. While in the control group, these 3 treatments were performed following the doctors' recommendations. Then the dose of warfarin was gradually adjusted to the stable dose according to the changes in the international standardized ratio. At the end of the 50 day experimental period, there were a greater number of patients in the experimental group who exhibited a stable blood concentration of warfarin than those in the control group (83.35 and 64.4%, respectively). In addition, the mean and median times for patients to obtain a stable dose in the experimental group were significantly shorter than those in the control group (mean, 18.2±1.7 and 27.3±2.0 days; and median, 11.7±1.1 and 20.5±1.8 days, respectively). The adverse reaction rate of the experimental group (9.5%) was markedly lower than that of the control group (26.7%). The occurrence of adverse reactions in the experimental group was also significantly later when compared with the control group (43.9±1.6 and 38.6±1.5 days, respectively). Furthermore, there was no significant difference between the average predicted dose (3.4±1.1 mg/day) and the average actual dose (3.5±1.4 mg/day; P=0.313). In conclusion, using the Lou type warfarin pharmacokinetic dosing algorithm equation to administer warfarin markedly shortened the adjustment time of warfarin to reach a stable dose and reduced the adverse reactions rate, thus supporting clinical feasibility.

Creating a genotype-based dosing algorithm for acenocoumarol steady dose

Acenocoumarol is a commonly prescribed anticoagulant drug for the prophylaxis and treatment of venous and arterial thromboembolic disorders in several countries. In counterpart of warfarin, there is scarce information about pharmacogenetic algorithms for steady acenocoumarol dose estimation. The aim of this study was to develop an algorithm of prediction for acenocoumarol.The algorithm was created using the data from 973 retrospectively selected anticoagulated patients and was validated in a second independent cohort adding up to 2,683 patients. The best regression model to predict stable dosage in the Primary Cohort included clinical factors (age and body mass index, BSA) and genetic variants (VKORC1, CYP2C9* and CYP4F2 polymorphisms) and explained up to 50% of stable dose. In the validation study the clinical algorithm yielded an adjusted R2=0.15 (estimation´s standard error=4.5) and the genetic approach improved the dose forecast up to 30% (estimation´s standard error=4.6). Again, the best model combined clinical and genetic factors (R2= 0.48; estimation´s standard error=4) which provided the best results of doses estimates within 20% of the real dose in patients taking lower (≤7mg/week) or higher (≥25mg/week) acenocoumarol doses. In conclusion, we developed a prediction algorithm using clinical data and three polymorphisms in VKORC1, CYP2C9* and CYP4F2 genes that provided a steady acenocoumarol dose for about 50% of patients in the Validation Cohort. Such algorithm was especially useful to patients who need higher or lower acenocoumarol doses, those patients with higher time required until their stabilisation and are more prone to suffer a treatment derived complication.

Genotype-guided therapy improves initial acenocoumarol dosing

A few trials so far have evaluated the effectiveness of algorithms designed to calculate doses in oral anticoagulant therapy, with negative or contradictory results. We compared a genotype-guided algorithm vs physician management for the initiation of acenocoumarol. In a twoarm, prospective, randomised study with patients with atrial fibrillation who started therapy, the first dose was administered to all patients according to the physician’s criteria. At 72 hours, the corresponding dose was calculated based on INR in the standard care group (SC, N=92), whereas genetic data (VKORC1, CYP2C9 and CYP4F2) were also considered for the genotype-guided dosing (pharmacogenetic) group (PGx, N=87) by using an algorithm previously validated in 2,683 patients. The primary outcomes were: patients with steady dose, the time needed to reach the same and the percentage of therapeutic INRs. After 90 days, 25 % of the SC and 39 % of the PGx patients reached the steady dose (p=0.038). Kaplan-Meier analysis showed that PGx group needed fewer days to reach therapeutic INR (p=0.033). Additionally, PGx had a higher percentage of therapeutic INRs than SC patients (50 % and 45 %, respectively) (p=0.046). After six months the proportion of steadily anticoagulated patients remained significantly higher in PGx (p=0.010). In conclusion, genotype-guided dosing was associated with a higher percentage of patients with steady dose than routine practice when starting oral anticoagulation with acenocoumarol.

Oral warfarin intake affects skin inflammatory cytokine responses in rats

Warfarin is an anticoagulant used in prevention/prophylaxis of thromboembolism. Besides the effects on coagulation, non-hemorrhagic reactions have also been documented. Although cutaneous reactions were reported in some patients, the impact on skin immunity was not explored. In the present paper, the effect of 30-day oral warfarin intake on skin cytokine responses in rats was analyzed. Increased release of inflammatory cytokines (TNF, IL-1β and IL-10) was noted by skin explants from rats which received warfarin, but without effect on IL-6. No impact on epidermal cell cytokine secretion was seen, except a tendency of an increase of IL-6 response to stimulation with microbial product lipopolysaccharide (LPS). Topical application of contact allergen dinitrochlorobenzene (DNCB) resulted in slight (numerical solely) increase of TNF release by skin explants of warfarin-treated animals, while epidermal cells responded by increased secretion of all four cytokines examined. The data presented provide new information on the potential of oral warfarin to modulate skin innate immune activity.

Phytonadione Education Program in a Community Hospital

Purpose

Pharmacists and physicians were educated regarding updated guidelines on phytonadione indications, dosing, and routes of administration. Study objectives were to evaluate the use of phytonadione in a community hospital, educate pharmacists and physicians about phytonadione use, and assess the value of education in terms of patient outcomes.

Methods

Baseline and follow-up data on phytonadione indications, dosages, and routes of administration were collected. Pretests and post-tests were administered before and after an education session. A Pharmacy and Therapeutics newsletter article highlighting the appropriate use of phytonadione was published.

Results

The baseline and follow-up medication use evaluations (MUEs) revealed that 53% and 62% of patients had an appropriate indication for phytonadione, respectively (P = 0.181). Among patients with an appropriate indication, 44% were administered an appropriate dose in the baseline group and 46% in the follow-up (P = 0.876). The baseline MUE revealed that 20% of phytonadione routes of administration were appropriate; 18% were considered appropriate in the follow-up (P = 0.842). Pharmacists' knowledge showed improvement after education efforts, with the mean score improving from 57% to 93.4% from pretest to post-test (P < 0.05) and the median score changing from 50% to 100%.

Conclusion

Improving pharmacists' knowledge is beneficial and necessary; however, it was not enough to change practice in this study. Additional steps must be taken to encourage routine application of the knowledge.

Oral warfarin affects some aspects of systemic immunomodulation with topical dinitrochlorobenzene (DNCB) in rats

PURPOSE

The efficacy of topical dinitrochlorobenzene (DNCB) in the treatment of some skin dermatoses is based both on local and systemic effects. It is not known, however, whether it can be applied to patients receiving some other therapy associated with systemic immunomodulation. The aim of the present paper using a rat model was to examine whether oral warfarin (WF) intake, as shown by others and by us, had an immunomodulatory potential to interfere with effects of topical DNCB as systemic immunotherapy.

MATERIALS AND METHODS

Rats received 3.5 mg/l of WF sodium in drinking water for 30 days and were thereafter skin-sensitized with 0.4% DNCB. Changes in the oxidative activity (myeloperoxidase/MPO, reduction of nitroblue tetrazolium/NBT and nitric oxide/NO production) as well as tumor necrosis factor (TNF) production by peripheral blood polymorphonuclear cells (PMN) were measured and compared with PMN from sensitized unexposed to WF rats.

RESULTS

WF intake enhanced some aspects of PMN activity (intracellular MPO activity and unstimulated NO production) as well as their responsiveness to exogenous stimulation (NBT reduction and TNF production from sensitized animals). However, WF also decreased PMN responsiveness of NO production to stimulation. WF affected NO and TNF production solely by PMN, as no effect on these activities of peripheral blood mononuclear cells was seen.

CONCLUSION

Having in mind that polymorphonuclear leukocytes are the most abundant cell type in peripheral blood in humans, increase of basic aspects of PMN activity described in the present paper might be relevant for consideration of using WF as therapeutic modality in patients topically treated with DNCB.

Strain differences in intestinal toxicity of warfarin in rats

Intestinal hemorrhage characterizes effectiveness of warfarin (WF) as rodenticide and is among adverse effects of therapy in humans. Having in mind genetic variations in the effectiveness of WF in wild rats and in the doses required for therapeutic effect, strain differences in the intestinal toxicity of oral warfarin in rats were examined in this study. High WF dose (3.5mg/l) led to mortality in Albino Oxford (AO) rats, with no lethality in Dark Agouti (DA) rats. Higher values of prothrombin time were noted at low WF dose (0.35mg/l) in the former strain. Leukocyte infiltration in intestine noted at this dose in both strains was associated with oxidative injury and more pronounced anti-oxidative response in AO rats. Suppression of mesenteric lymph node cell proliferation and IFN-γ and IL-10 production in AO rats and lack of these effects in DA rats, represent different strategies to protect vulnerable intestine from harmful immune responses.

Novel oral anticoagulants for acute coronary syndrome

Acute coronary syndrome (ACS) is a cardiovascular condition with a multifactorial pathophysiology that includes atherosclerotic plaques, platelet activation and thrombin production, among others. Thrombin production and the prothrombotic state of ACS patients have provided a role for anticoagulants to treat patients during the acute event and has led to subsequent research for the post-acute state. Warfarin has an indication for ACS, however, it is restricted to specific patients and many factors limit its use. Therefore, novel oral anticoagulants (NOACs) are being explored for ACS. Limitations for the use of NOACs in ACS are centered on the increased risk of bleeding that occurs when these agents are added to the current standard of care with dual antiplatelet therapy. Rivaroxaban is the only NOAC that has achieved approval in Europe for this indication with none of the NOAC currently approved in the US for use in ACS. Ongoing studies for rivaroxaban and apixaban may provide evidence to further clarify the place in therapy for NOAC agents in ACS management.

Hematology in palliative medicine

Advanced cancer and life-limiting chronic nonmalignant diseases are associated with a number of hematological problems. Anemia and coagulation disorders, principally venous thrombosis and thrombocytopenia, are most commonly observed. Patients undergoing chemotherapy and bone marrow transplant have unique problems that include neutropenias and chemotherapy-induced drug toxicities, which will not be covered in this article.

An expanded pharmacogenomics warfarin dosing table with utility in generalised dosing guidance

Pharmacogenomics (PGx) guided warfarin dosing, using a comprehensive dosing algorithm, is expected to improve dose optimisation and lower the risk of adverse drug reactions. As a complementary tool, a simple genotype-dosing table, such as in the US Food and Drug Administration (FDA) Coumadin drug label, may be utilised for general risk assessment of likely over- or under-anticoagulation on a standard dose of warfarin. This tool may be used as part of the clinical decision support for the interpretation of genetic data, serving as a first step in the anticoagulation therapy decision making process. Here we used a publicly available warfarin dosing calculator (www.warfarindosing.org) to create an expanded gene-based warfarin dosing table, the CPMC-WD table that includes nine genetic variants in CYP2C9, VKORC1, and CYP4F2. Using two datasets, a European American cohort (EUA, n=73) and the Quebec Warfarin Cohort (QWC, n=769), we show that the CPMC-WD table more accurately predicts therapeutic dose than the FDA table (51 % vs 33 %, respectively, in the EUA, McNemar's two-sided p=0.02; 52 % vs 37 % in the QWC, p<1×10(-6)). It also outperforms both the standard of care 5 mg/day dosing (51 % vs 34 % in the EUA, p=0.04; 52 % vs 31 % in the QWC, p<1×10(-6)) as well as a clinical-only algorithm (51 % vs 38 % in the EUA, trend p=0.11; 52 % vs 45 % in the QWC, p=0.003). This table offers a valuable update to the PGx dosing guideline in the drug label.

Prediction of bleeding events in patients with venous thromboembolism on stable anticoagulation treatment

Attempts at identifying patients with an elevated risk of bleeding while on anticoagulation following acute venous thromboembolism (VTE) have largely been unsuccessful thus far. We sought to develop a clinical prediction score for bleeding during stable anticoagulation treatment after acute VTE.

We performed a post hoc analysis of the pooled RE-COVER studies, two double-blind randomised “sister” trials evaluating dabigatran versus standard treatment in 5107 VTE patients.

A score was derived from patients randomised to dabigatran using logistic regression analysis covering the complete follow-up period. The final model, named VTE-BLEED, included six variables and yielded a c-statistic of 0.72 (95% CI 0.67–0.76). Patients from the derivation cohort in the low-risk group (<2 points; 74% of the derivation population) had a bleeding incidence of 2.8% compared to 12.6% in the elevated-risk group (OR 5.0; 95% CI 3.5–7.1). The score proved accurate for our primary end-point, i.e. prediction of major bleeding after day 30 (“stable” anticoagulation), both in patients on dabigatran (c-statistic 0.75, 95% CI 0.61–0.89) and those on warfarin (0.78, 95% CI 0.68–0.86; p=0.77 for difference).

The new VTE-BLEED score accurately predicted major bleeding events in VTE patients on stable anticoagulation with both dabigatran and warfarin.

Self-monitoring and self-management of oral anticoagulation

BACKGROUND

The introduction of point-of-care devices for the management of patients on oral anticoagulation allows self-testing by the patient at home. Patients who self-test can either adjust their medication according to a pre-determined dose-INR (international normalized ratio) schedule (self-management), or they can call a clinic to be told the appropriate dose adjustment (self-monitoring). Increasing evidence suggests self-testing of oral anticoagulant therapy is equal to or better than standard monitoring. This is an updated version of the original review published in 2010.

OBJECTIVES

To evaluate the effects on thrombotic events, major haemorrhages, and all-cause mortality of self-monitoring or self-management of oral anticoagulant therapy compared to standard monitoring.

SEARCH METHODS

For this review update, we re-ran the searches of the Cochrane Central Register of Controlled Trials (CENTRAL), 2015, Issue 6, the Cochrane Library, MEDLINE (Ovid, 1946 to June week 4 2015), Embase (Ovid, 1980 to 2015 week 27) on 1 July 2015. We checked bibliographies and contacted manufacturers and authors of relevant studies. We did not apply any language restrictions .

SELECTION CRITERIA

Outcomes analysed were thromboembolic events, mortality, major haemorrhage, minor haemorrhage, tests in therapeutic range, frequency of testing, and feasibility of self-monitoring and self-management.

DATA COLLECTION AND ANALYSIS

Review authors independently extracted data and we used a fixed-effect model with the Mantzel-Haenzel method to calculate the pooled risk ratio (RR) and Peto's method to verify the results for uncommon outcomes. We examined heterogeneity amongst studies with the Chi(2) and I(2) statistics and used GRADE methodology to assess the quality of evidence.

MAIN RESULTS

We identified 28 randomised trials including 8950 participants (newly incorporated in this update: 10 trials including 4227 participants). The overall quality of the evidence was generally low to moderate. Pooled estimates showed a reduction in thromboembolic events (RR 0.58, 95% CI 0.45 to 0.75; participants = 7594; studies = 18; moderate quality of evidence). Both, trials of self-management or self-monitoring showed reductions in thromboembolic events (RR 0.47, 95% CI 0.31 to 0.70; participants = 3497; studies = 11) and (RR 0.69, 95% CI 0.49 to 0.97; participants = 4097; studies = 7), respectively; the quality of evidence for both interventions was moderate. No reduction in all-cause mortality was found (RR 0.85, 95% CI 0.71 to 1.01; participants = 6358; studies = 11; moderate quality of evidence). While self-management caused a reduction in all-cause mortality (RR 0.55, 95% CI 0.36 to 0.84; participants = 3058; studies = 8); self-monitoring did not (RR 0.94, 95% CI 0.78 to 1.15; participants = 3300; studies = 3); the quality of evidence for both interventions was moderate. In 20 trials (8018 participants) self-monitoring or self-management did not reduce major haemorrhage (RR 0.95, 95% CI, 0.80 to 1.12; moderate quality of evidence). There was no significant difference found for minor haemorrhage (RR 0.97, 95% CI 0.67 to 1.41; participants = 5365; studies = 13). The quality of evidence was graded as low because of serious risk of bias and substantial heterogeneity (I(2) = 82%).

AUTHORS' CONCLUSIONS

Participants who self-monitor or self-manage can improve the quality of their oral anticoagulation therapy. Thromboembolic events were reduced, for both those self-monitoring or self-managing oral anticoagulation therapy. A reduction in all-cause mortality was observed in trials of self-management but not in self-monitoring, with no effects on major haemorrhage.

[Spontaneous hematoma of right angle of the transverse mesocolon: exceptional complication of anticoagulant therapy with vitamin K]

L'hématome spontané du méso de l'angle colique droit et du transverse est une complication rare du traitement anticoagulant par antivitamine K. Nous rapportons un cas d'hématome spontané du méso de l'angle colique droit et du transverse associé à un hémopéritoine de grande abondance chez un patient traité par antivitamine K pour embolie pulmonaire consécutive à une fracture des plateaux tibiaux droits. Le diagnostic doit être fait en urgence. L’échographie abdominale et la tomodensitométrie confirment le diagnostic. Le traitement non opératoire est la règle. Le traitement chirurgical est indiqué en cas de complications telles que la rupture de l'hématome.

Intestinal toxicity of oral warfarin intake in rats

Though warfarin is extensively used in the prevention and treatment of thromboembolic processes in humans, adverse effects of warfarin therapy have been recognized. Intestinal hemorrhage is one of the hazards of anticoagulant therapy, but the mechanisms of warfarin toxicity are virtually unknown. In this work, the effects of 30 days oral warfarin (0.35 mg/l and 3.5 mg/l) intake on rat's gut were examined. Both doses resulted in prolongation of prothrombin time. Systemic effects of higher warfarin dose (increases in plasma AST, proteinuria, hematuria, changes in peripheral blood hematological parameters) were seen. Warfarin intake resulted in histologically evident tissue damage, leukocyte infiltration and intestinal inflammation [increases in myeloperoxidase activity, malondialdehyde content, superoxide dismutase and catalase activity, proinflammatory cytokine (IFN-γ, IL-17) concentrations in intestinal homogenates]. In contrast, suppression of gut-draining mesenteric lymph node (MLN) cell activity [proliferation responsiveness, production of IFN-γ and IL-17 to T lymphocyte mitogen Concanavalin A stimulation] was noted. Inhibition of regulatory cytokine IL-10 production by MLN cells, suggests commitment of MLN to the suppression of all inflammatory activities and creation of the microenvironment which is non-permissive for induction of potentially harmful immune response. These novel findings indicate the need of staying alert for (adverse) effects of warfarin therapy.

Point-of-care diagnostics for niche applications

Point-of-care or point-of-use diagnostics are analytical devices that provide clinically relevant information without the need for a core clinical laboratory. In this review we define point-of-care diagnostics as portable versions of assays performed in a traditional clinical chemistry laboratory. This review discusses five areas relevant to human and animal health where increased attention could produce significant impact: veterinary medicine, space travel, sports medicine, emergency medicine, and operating room efficiency. For each of these areas, clinical need, available commercial products, and ongoing research into new devices are highlighted.

Genetic polymorphisms of pharmacogenomic VIP variants in Li nationality of southern China

OBJECTIVES

The present study aimed to screen members of the Li nationality in southern China for genotype frequencies of VIP variants and to determine differences between the Li ethnicity and global human population samples in HapMap.

METHODS

In this study, we genotyped 77 very important pharmacogenetic (VIP) variants selected from the pharmacogenomics knowledge base (PharmGKB) in members of the Li population and compared our data with other eleven populations from the HapMap data set.

RESULTS

Our results showed that VDR rs1540339, VKORC1 rs9934438, and MTHFR rs1801133 were most different in Li compared with most of the eleven populations from the HapMap data set. Furthermore, population structure and F-statistics (Fst) analysis also showed differences between the Li and other HapMap populations, and the results suggest that the Li are most genetically similar to the CHD population, and the least similar to the YRI in HapMap.

CONCLUSIONS

The findings of our study complement the pharmacogenomics database with information on members of the Li ethnicity and provide a stronger scientific basis for safer drug administration, which may help clinicians to predict individual drug responses, thereby avoiding the risk of adverse effects and optimizing efficacy in this population.

A phase I clinical trial of the effect of belinostat on the pharmacokinetics and pharmacodynamics of warfarin

PURPOSE

Belinostat is a potent small molecule inhibitor that exerts its antitumor effect through inhibition of histone deacetylase. The purpose of this study was to evaluate the pharmacokinetics and pharmacodynamics of warfarin (as a reference drug metabolized by CYP2C9) in the presence and absence of belinostat.

METHODS

We conducted a phase I, single-center, open-label, drug-drug interaction study between belinostat and warfarin. In part I, patients were given warfarin 5 mg orally (day-14 and 3) and belinostat 1000 mg/m(2) (days 1 through 5). Patients receiving benefit continued belinostat on days 1 through 5 every 21 days until disease progression, unacceptable toxicity, or per patient preference.

RESULTS

A total of 18 patients were treated. With belinostat, the least-squared means for maximum concentration (C max), area under the curve0-∞, and area under the curve0-t of R-warfarin were slightly increased. However, for the more potent S-warfarin isomer, the same parameters were primarily contained within the pre-specified equivalence limits of 0.80 and 1.25, indicating there was no statistically significant interaction between S-warfarin and belinostat. The most common adverse events were nausea, vomiting, and fatigue. Three grade 3 adverse events (diarrhea 5.6 %, nausea 5.6 %, and vomiting 5.6 %) were thought to be treatment related. Progression-free survival ranged from 0.2 to 13.8 months in all patients.

CONCLUSIONS

Belinostat did not significantly affect the pharmacokinetics and pharmacodynamics of warfarin, indicating no clinically relevant effect on the enzymatic activity of CYP2C9.

Clinical Factors and Perioperative Strategies Associated with Outcome in Preinjury Antiplatelet and Anticoagulation Therapy for Patients with Traumatic Brain Injuries

Objective

Long-term oral anticoagulation or antiplatelet therapy has been used with increasing frequency in the elderly. These patients are at increased risk of morbidity and mortality from expansion of intracranial hemorrhage. We conducted a single-center retrospective case control study to evaluate risk factors associated with outcomes and to identify the differences in outcome in traumatic brain injury between preinjury anticoagulation use and without anticoagulation.

Methods

A retrospective study of patients who underwent craniotomy or craniectomy for acute traumatic cerebral hemorrhage, between January 2005 and December 2014 was performed.

Results

A consecutive series of 50 patients were evaluated. The factors significantly differed between the two groups were initial Prothrombin Time-International Normalized Ratio, initial platelet count, initial Glasgow Coma Scale score, and postoperative intracranial bleeding. Mean Glasgow Outcome Scale (GOS) score were similar between the two groups. In the patient with low-energy trauma only, no significant differences in GOS score, postoperative bleeding and many other factors were observed. The contributing factors to postoperative bleeding was preinjury anticoagulation and its adjusted odds ratio was 12 [adjusted odds ratio (OR), 12.242; p=0.0070]. The contributing factors to low GOS scores, which mean unfavorable neurological outcomes, were age (adjusted OR, 1.073; p=0.039) and Rotterdam scale score for CT scans (adjusted OR, 3.123; p=0.0020).

Conclusion

Preinjury anticoagulation therapy contributed significantly to the occurrence of postoperative bleeding. However, preinjury anticoagulation therapy in the patients with low-energy trauma did not contribute to the poor clinical outcomes or total hospital stay. Careful attention should be given to older patients and severity of hemorrhage on initial brain CT.

New insights into the mechanisms of action of aspirin and its use in the prevention and treatment of arterial and venous thromboembolism

The antithrombotic action of aspirin has long been recognized. Aspirin inhibits platelet function through irreversible inhibition of cyclooxygenase (COX) activity. Until recently, aspirin has been mainly used for primary and secondary prevention of arterial antithrombotic events. The aim of this study was to review the literature with regard to the various mechanisms of the newly discovered effects of aspirin in the prevention of the initiation and development of venous thrombosis. For this purpose, we used relevant data from the latest numerous scientific studies, including review articles, original research articles, double-blinded randomized controlled trials, a prospective combined analysis, a meta-analysis of randomized trials, evidence-based clinical practice guidelines, and multicenter studies. Aspirin is used in the prevention of venous thromboembolism (VTE), especially the prevention of recurrent VTE in patients with unprovoked VTE who were treated with vitamin K antagonists (VKAs) or with non-vitamin K antagonist oral anticoagulants (NOACs). Numerous studies have shown that aspirin reduces the rate of recurrent VTE in patients, following cessation of VKAs or NOACs. Furthermore, low doses of aspirin are suitable for long-term therapy in patients recovering from orthopedic or other surgeries. Aspirin is indicated for the primary and secondary prevention as well as the treatment of cardiovascular diseases, including acute coronary syndrome, myocardial infarction, peripheral artery disease, acute ischemic stroke, and transient ischemic attack (especially in atrial fibrillation or mechanical heart valves). Aspirin can prevent or treat recurrent unprovoked VTEs as well as VTEs occurring after various surgeries or in patients with malignant disease. Recent trials have suggested that the long-term use of low-dose aspirin is effective not only in the prevention and treatment of arterial thrombosis but also in the prevention and treatment of VTE. Compared with VKAs and NOACs, aspirin has a reduced risk of bleeding.

New oral anticoagulants: their advantages and disadvantages compared with vitamin K antagonists in the prevention and treatment of patients with thromboembolic events

Despite the discovery and application of many parenteral (unfractionated and low-molecular-weight heparins) and oral anticoagulant vitamin K antagonist (VKA) drugs, the prevention and treatment of venous and arterial thrombotic phenomena remain major medical challenges. Furthermore, VKAs are the only oral anticoagulants used during the past 60 years. The main objective of this study is to present recent data on non-vitamin K antagonist oral anticoagulants (NOACs) and to analyze their advantages and disadvantages compared with those of VKAs based on a large number of recent studies. NOACs are novel direct-acting medications that are selective for one specific coagulation factor, either thrombin (IIa) or activated factor X (Xa). Several NOACs, such as dabigatran (a direct inhibitor of FIIa) and rivaroxaban, apixaban and edoxaban (direct inhibitors of factor Xa), have been used for at least 5 years but possibly 10 years. Unlike traditional VKAs, which prevent the coagulation process by suppressing the synthesis of vitamin K-dependent factors, NOACs directly inhibit key proteases (factors IIa and Xa). The important indications of these drugs are the prevention and treatment of deep vein thrombosis and pulmonary embolisms, and the prevention of atherothrombotic events in the heart and brain of patients with acute coronary syndrome and atrial fibrillation. They are not fixed, and dose-various strengths are available. Most studies have reported that more advantages than disadvantages for NOACs when compared with VKAs, with the most important advantages of NOACs including safety issues (ie, a lower incidence of major bleeding), convenience of use, minor drug and food interactions, a wide therapeutic window, and no need for laboratory monitoring. Nonetheless, there are some conditions for which VKAs remain the drug of choice. Based on the available data, we can conclude that NOACs have greater advantages and fewer disadvantages compared with VKAs. New studies are required to further assess the efficacy of NOACs.

Assessment of bleeding during minor oral surgical procedures and extraction in patients on anticoagulant therapy

Introduction:

The risk of postoperative hemorrhage from oral surgical procedures has been a concern in the treatment of patients who are receiving long-term anticoagulation therapy. A study undertaken in our institution to address questions about the amount and severity of bleeding associated with minor outpatient oral surgery procedures by assessing bleeding in patients who did not alter their anticoagulant regimen.

Subjects and Methods:

Eighty-three patients receiving long-term anticoagulant therapy visited Department of Oral and Maxillofacial Surgery from May 2010 to October 2011 for extractions and minor oral surgical procedures. Each patient was required to undergo preoperative assessment of prothrombin time (PT) and measurement of the international normalized ratio. Fifty-six patients with preoperative PT values within the therapeutic range 3–4 were included in the study. The patients’ age ranged between 30 and 75 years. Application of surgispon was done following the procedure. Extraction of teeth performed with minimal trauma to the surrounding tissues, the socket margins sutured, and sutures removed after 5 days.

Results:

There was no significant incidence of prolonged or excessive hemorrhage and wound infection and the healing process was normal.

Simplified Warfarin Dose-response Pharmacodynamic Models

Warfarin is a frequently used oral anticoagulant for long-term prevention and treatment of thromboembolic events. Due to its narrow therapeutic range and large inter-individual dose-response variability, it is highly desirable to personalize warfarin dosing. However, the complexity of the conventional kinetic-pharmacodynamic (K-PD) models hampers the development of the personalized dose management. To avert this challenge, we propose simplified PD models for warfarin dose-response relationship, which is motivated by ideas from control theory. The simplified models were further applied to longitudinal data of 37 patients undergoing anticoagulation treatment using the standard two-stage approach and then compared with the conventional K-PD models. Data analysis shows that all models have a similar predictive ability, but the simplified models are most parsimonious.

Serum albumin binding analysis and toxicological screening of novel chroman-2,4-diones as oral anticoagulants

Two chroman-2,4-dione derivatives, namely 2a and 2f, were tested as in vivo anticoagulants by seven days of continuous per os application to adult male Wistar rats in a concentration of 20 mg/kg of body weight. Derivatives were selected from a group of six previously intraperitoneally applied compounds on the basis of presenting remarkable activity in a concentration of 2 mg/kg of body weight. The derivatives 2a and 2f are VKORC1 inhibitors, and comparison of the absorption spectra, association, and dissociation constants suggested that the compounds will be bound to serum albumin in the same manner as warfarin is, leading to transfer towards the molecular target VKORC1. After oral administration, the compounds proved to be anticoagulants comparable with warfarin, inasmuch as the measured prothrombin times for 2a and 2f were 56.63 and 60.08 s, respectively. The INR values of 2a and 2f ranged from 2.6 to 2.8, recommending them as useful therapeutics in the treatment of patients suffering from thromboembolic events and atrial fibrillation. The high percentage of binding and high binding affinity of 2a and 2f towards serum albumin reduced the risk of induced internal bleeding. Several kinds of toxicity studies were performed to investigate whether or not 2a and 2f can cause pathological changes in the liver, kidneys, and DNA. The catalytic activity of serum enzymes, concentration and catalytic activity of liver and kidney oxidative stress markers and enzymes, respectively, as well as the observed hepatic and renal morphological changes indicated that the compounds in relation to warfarin induced irrelevant hepatic toxicity, no increment of necrosis, and inconsiderable oxidative damage in the liver and kidneys. Estimation of DNA damage using the comet assay confirmed that 2a and 2f caused no clinically significant genotoxicity. The higher activity and lower toxicity of 2f recommended this compound as a better drug candidate than 2a.