scholarly journals A Review of Warfarin Dosing and Monitoring

2018 ◽  
Vol 13 (1) ◽  
pp. 40-43 ◽  
Author(s):  
Khan Md Arif ◽  
Mohammad Ashiqur Rahman
Keyword(s):  
Venous Thromboembolism ◽  
Heart Valves ◽  
Warfarin Therapy ◽  
Thrombus Formation ◽  
Therapeutic Index ◽  
International Normalized Ratio ◽  
Major Surgery ◽  
Clotting Factors ◽  
Duration Of Treatment ◽  
Oral Anticoagulant Treatment

The anticoagulant drug warfarin is a vitamin K antagonist, coumarin derivative which inhibits the synthesis of clotting factors II, VII, IX, and X, as well as the naturally occurring endogenous anticoagulant proteins C and S. Warfarin is still considered the mainstay of oral anticoagulant treatment, it is a difficult drug to manage due to its narrow therapeutic index. An inappropriate management of patients can lead to subtherapeutic or supratherapeutic levels, increasing the risk of thromboembolic episodes or hemorrhagic episodes, respectively. Common indications for the use of warfarin include stroke prevention in atrial fibrillation, preventing thrombus formation in patients with heart valves and treatment of venous thromboembolism. When warfarin therapy is initiated for venous thromboembolism, it should be given the first day, along with a heparin product or fondaparinux. The heparin product or fondaparinux should be continued for at least five days and until the patient's international normalized ratio is at least 2.0 for two consecutive days. The international normalized ratio goal and duration of treatment with warfarin vary depending on indication and risk. Warfarin therapy should be stopped five days before major surgery and restarted 12 to 24 hours postoperatively. Bridging with low-molecular-weight heparin or other agents is based on balancing the risk of throm boembolism with the risk of bleeding.Faridpur Med. Coll. J. Jan 2018;13(1): 40-43

Patient Factors That Influence Warfarin Dose Response

2010 ◽  
Vol 23 (3) ◽  
pp. 194-204 ◽  
Author(s):  
Pamela J. White
Keyword(s):  
Dose Response ◽  
Warfarin Therapy ◽  
Anticoagulation Therapy ◽  
Warfarin Dose ◽  
Therapeutic Index ◽  
International Normalized Ratio ◽  
Patient Factors ◽  
Disease States ◽  
Treatment And Prevention ◽  
Number Of Factors

Warfarin has long been the mainstay of oral anticoagulation therapy for the treatment and prevention of venous and arterial thrombosis. The narrow therapeutic index of warfarin, and the complex number of factors that influence international normalized ratio (INR) response, makes optimization of warfarin therapy challenging. Determination of the appropriate warfarin dose during initiation and maintenance therapy requires an understanding of patient factors that influence dose response: age, body weight, nutritional status, acute and chronic disease states, and changes in concomitant drug therapy and diet. This review will examine specific clinical factors that can affect the pharmacokinetics and pharmacodynamics of warfarin, as well as the role of pharmacogenetics in optimizing warfarin therapy.

Influence of thrombophilia on risk of recurrent venous thromboembolism while on warfarin: results from a randomized trial

Blood ◽  
2008 ◽  
Vol 112 (12) ◽  
pp. 4432-4436 ◽  
Author(s):  
Clive Kearon ◽  
Jim A. Julian ◽  
Michael J. Kovacs ◽  
David R. Anderson ◽  
Philip Wells ◽  
...  
Keyword(s):  
Venous Thromboembolism ◽  
Warfarin Therapy ◽  
Factor V Leiden ◽  
International Normalized Ratio ◽  
Antiphospholipid Antibody ◽  
Factor V ◽  
Antithrombin Deficiency ◽  
Recurrent Venous Thromboembolism ◽  
Prothrombin Gene Mutation ◽  
Recurrent Vte

Abstract We sought to determine whether thrombophilic defects increase recurrent venous thromboembolism (VTE) during warfarin therapy. Six hundred sixty-one patients with unprovoked VTE who were randomized to extended low-intensity (international normalized ratio [INR], 1.5-1.9) or conventional-intensity (INR, 2.0-3.0) anticoagulant therapy were tested for thrombophilia and followed for a mean of 2.3 years. One or more thrombophilic defects were present in 42% of patients. The overall rate of recurrent VTE was 0.9% per patient-year. Recurrent VTE was not increased in the presence of factor V Leiden (hazard ratio [HR], 0.7; 95% CI, 0.2-2.6); the 20210G>A prothrombin gene mutation (HR, 0); antithrombin deficiency (HR, 0); elevated factor VIII (HR, 0.7; 95% CI, 0.1-5.4); elevated factor XI (HR, 0.7; 95% CI, 0.1-5.0), or elevated homocysteine (HR, 0.7; 95% CI, 0.1-5.3), but showed a trend to an increase with an antiphospholipid antibody (HR, 2.9; 95% CI, 0.8-10.5). Compared with patients with no thrombophilic defects, the rate of recurrence was not increased in the presence of one (HR, 0.7; 95% CI, 0.2-2.3) or more than one (HR, 0.7; 95% CI, 0.2-3.4) defect. We conclude that single or multiple thrombophilic defects are not associated with a higher risk of recurrent VTE during warfarin therapy.

scholarly journals Genetic-based dosing in orthopedic patients beginning warfarin therapy

Blood ◽  
2007 ◽  
Vol 110 (5) ◽  
pp. 1511-1515 ◽  
Author(s):  
Eric A. Millican ◽  
Petra A. Lenzini ◽  
Paul E. Milligan ◽  
Leonard Grosso ◽  
Charles Eby ◽  
...  
Keyword(s):  
Warfarin Therapy ◽  
Smoking Status ◽  
Warfarin Dose ◽  
Therapeutic Index ◽  
International Normalized Ratio ◽  
Narrow Therapeutic Index ◽  
Therapy Initiation ◽  
Estimated Blood Loss ◽  
Epoxide Reductase ◽  
Orthopedic Patients

AbstractHigh variability in drug response and a narrow therapeutic index complicate warfarin therapy initiation. No existing algorithm provides recommendations on refining the initial warfarin dose based on genetic variables, clinical data, and international normalized ratio (INR) values. Our goal was to develop such an algorithm. We studied 92 patients undergoing primary or revision total hip or knee replacement. From each patient we collected a blood sample, clinical variables, current medications, and preoperative and postoperative laboratory values. We genotyped for polymorphisms in the cytochrome P450 (CYP) 2C9 and vitamin K epoxide reductase (VKORC1) genes. Using stepwise regression, we developed a model for refining the warfarin dose after the third warfarin dose. The algorithm explained four fifths of the variability in therapeutic dose (R2adj of 79%). Significant (P > .05) predictors were INR value after 3 doses (47% reduction per 0.25-unit rise), first warfarin dose (+7% per 1 mg), CYP2C9*3 and CYP2C9*2 genotype (−38% and −17% per allele), estimated blood loss (interacting with INR3), smoking status (+20% in current smokers), and VKORC1 (−11% per copy of haplotype A). If validated, this model should provide a safer, more effective process for initiating warfarin therapy.

Monitoring Warfarin Therapy with the International Normalized Ratio

1994 ◽  
Vol 28 (2) ◽  
pp. 242-244 ◽  
Author(s):  
Patricia A. Howard
Keyword(s):  
Ct Scan ◽  
Heart Valves ◽  
Warfarin Therapy ◽  
Medical Center ◽  
Current System ◽  
International Normalized Ratio ◽  
Bleeding Complications ◽  
Warfarin Dosage ◽  
Local Hospital ◽  
Traditional System

OBJECTIVE: To report a case of suboptimal warfarin monitoring. CASE SUMMARY: A patient with a history of rheumatic heart disease and a mechanical mitral valve was admitted to the local hospital complaining of left-sided weakness. At the time, she was receiving warfarin 5 mg/d. Upon admission her prothrombin time (PT) was 15 s. An initial computed tomography (CT) scan of the head was negative. On the basis of the initial findings, it was unclear whether the symptoms were caused by a cerebrovascular accident (CVA). The patient was transferred to the University Medical Center for a more thorough evaluation. The diagnosis of CVA was confirmed by a repeat CT scan seven days after the event. On the basis of the information obtained from the local hospital, it was determined that the initial PT of 15 s converted to an International Normalized Ratio (INR) of 1.5, which is below the recommended range for patients with mechanical heart valves. Prior to discharge, the warfarin dosage was increased to obtain an INR in the recommended range of 2.5–3.5. DISCUSSION: This case illustrates the problems that exist with the current system of PT reporting and the potential advantages of using the INR. Variations in the sensitivity of the thromboplastin reagents used to perform the PT may result in misinterpretation of the level of anticoagulation and errors in warfarin dosage adjustments. The potential for suboptimal anticoagulation is greatly increased in patients, such as the one reported here, who are having PTs performed by multiple laboratories. CONCLUSIONS: To maximize efficacy and minimize the risk of bleeding complications, warfarin therapy must be individualized and closely monitored. Standardization of PT monitoring through the use of the INR would significantly reduce the potential for suboptimal anticoagulation associated with the traditional system of reporting.

scholarly journals Long-Term Management of Venous Thromboembolism: Lessons from EINSTEIN CHOICE and Other Extension Trials

2019 ◽  
Vol 119 (05) ◽  
pp. 689-694 ◽  
Author(s):  
Jeffrey Weitz ◽  
Noel Chan
Keyword(s):  
Venous Thromboembolism ◽  
Randomized Clinical Trials ◽  
Vitamin K Antagonists ◽  
Oral Anticoagulants ◽  
International Normalized Ratio ◽  
Choice Trial ◽  
Major Surgery ◽  
Risk Of Recurrence ◽  
Coagulation Monitoring ◽  
Risk Of Bleeding

Many patients with venous thromboembolism (VTE) are at risk of recurrence if anticoagulant therapy is stopped. Whereas 3 months of anticoagulation treatment is sufficient for patients with VTE provoked by major surgery or trauma, in many cases a longer course is needed. Extended therapy with vitamin K antagonists (VKAs) requires frequent coagulation monitoring and dose adjustments to ensure that the international normalized ratio (INR) remains within the therapeutic range; furthermore, there is a risk of major bleeding even if a therapeutic INR is maintained. Therefore, more convenient and safer anticoagulants are needed.The non-VKA oral anticoagulants (NOACs)—apixaban, dabigatran, edoxaban and rivaroxaban—simplify extended therapy because they can be given in fixed doses without routine coagulation monitoring. Randomized clinical trials have demonstrated the efficacy and safety of NOACs for extended VTE treatment, but bleeding remains a concern. Patients and physicians may, therefore, be reluctant to continue anticoagulation beyond 3 to 6 months except in patients at high risk of recurrence. Acetylsalicylic acid (ASA) is often prescribed instead of an anticoagulant because of its perceived lower risk of bleeding; however, the recent EINSTEIN CHOICE trial demonstrated that once-daily rivaroxaban at a dose of either 20 or 10 mg reduced the risk of recurrent VTE by 70% compared with ASA without significantly increasing the risk of bleeding. In this review, we discuss the EINSTEIN CHOICE trial in the context of previous trials for extended VTE treatment and examine some of the lessons that can be applied to clinical practice.

scholarly journals Assessment of Anticoagulation Control Association with Warfarin Knowledge and Demographic Features of Iranian Population

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Mohammad Esmaeel Zangenehfar ◽  
Iman Harirforoosh ◽  
Bahram Mohebbi ◽  
Zahra Khajali
Keyword(s):  
Heart Valves ◽  
Health Care Systems ◽  
Therapeutic Index ◽  
International Normalized Ratio ◽  
Cross Sectional Study ◽  
Anticoagulation Clinic ◽  
Prosthetic Heart Valves ◽  
Cross Sectional ◽  
Vein Thrombosis ◽  
Anticoagulation Control

Background: Warfarin is the most commonly used oral anticoagulant for patients with atrial fibrillation, prosthetic heart valves, and deep vein thrombosis with a narrow therapeutic index. Due to the importance of patients’ adherence to treatment and also regular measurements of International normalized ratio (INR), this can have a significant impact on the quality of anticoagulation control. Objectives: The primary aim of this study was to assess the association between warfarin knowledge and time in therapeutic range (TTR) in patients on warfarin anticoagulation for at least 6 months who were referred to anticoagulation clinic in Rajaie Heart Center during 2016 - 2017. Methods: In this cross-sectional study, 620 patients who had been referred to the outpatient Rajaie Hospital anticoagulant clinic and had been taking warfarin for over six months were asked to fill two questionnaires named anticoagulation knowledge assessment (AKA) during a 12-week period. After obtaining the necessary permits, TTR (by Rosendal method) was calculated using the INR results of patients. Results: A total of 620 patients completed the questionnaire. The relation between warfarin knowledge and anticoagulation control was not significant. The mean age of the study population was 52.45 SD ± 14.01 years. This study showed a significant relationship between TTR, duration of warfarin usage (PV = 0.03) and the underlying cause of this usage (PV = 0.016). Conclusions: Prevention of chronic diseases is one of the most important priorities of the health care systems. Reduction in complications such as thrombosis and bleeding can be achieved by efforts to promote patient’s knowledge. By recognition of relation between warfarin knowledge and social and demographic indicators, patient’s education gap can be detected and also planned for dissolving. This study showed that although many of the patients visited in anticoagulation clinic have poor anticoagulation control, but a major part of them have good knowledge of warfarin usage.

Khat Chewing Effect on the International Normalized Ratio in Patients with Mechanical Heart Valves under Warfarin Therapy

2020 ◽  
Vol 23 (11) ◽  
pp. 1487-1491
Author(s):  
Sultan Abdulwadou ◽  
Nouradden Noman Alja ◽  
Abdulwahab Omer Hussa ◽  
Khalid Mohammed A ◽  
Suliman Gafar Sali
Keyword(s):  
Heart Valves ◽  
Warfarin Therapy ◽  
International Normalized Ratio ◽  
Mechanical Heart Valves ◽  
Khat Chewing

scholarly journals Extended-Duration Low-intensity Apixaban to Prevent Recurrence in Patients with Provoked Venous Thromboembolism: Design of the HI-PRO Trial

2021 ◽  
Author(s):  
Behnood Bikdeli ◽  
Heather Hogan ◽  
Ruth Morrison ◽  
John Fanikos ◽  
Umberto Campia ◽  
...  
Keyword(s):  
Risk Factors ◽  
Venous Thromboembolism ◽  
Standard Dose ◽  
Major Surgery ◽  
Duration Of Treatment ◽  
Double Blind ◽  
Safety Outcome ◽  
Low Intensity ◽  
Peripheral Ischemia ◽  
Extended Duration

Patients with acute venous thromboembolism (VTE) in the setting of transient provoking factors are typically treated with short-term anticoagulation. However, the risk of recurrence may be increased in the presence of enduring risk factors. In such patients, the optimal duration of treatment remains uncertain. HI-PRO is a single-center, double-blind randomized trial. Patients with deep vein thrombosis (DVT) or pulmonary embolism (PE) following a major provoking factor, including major surgery or major trauma, who completed at least 3 months of standard-dose therapeutic anticoagulation and have at least one enduring risk factor (such as obesity or heart failure), will be considered for inclusion. Patients will be randomized to apixaban 2.5 mg twice daily or placebo for 12 months. The primary efficacy outcome will be symptomatic recurrent VTE –a composite of DVT and/or PE at 12 months after randomization. Secondary efficacy outcomes include a composite of death due to cardiovascular causes, nonfatal myocardial infarction, stroke or systemic embolism, major adverse limb events, or coronary or peripheral ischemia requiring revascularization at 12 months, and individual components of these outcomes. The primary safety outcome is major bleeding according to the International Society on Thrombosis and Haemostasis definition. The study plans to enroll 600 patients (300 per arm) to have 80% power for detecting a 75% relative risk reduction in the primary outcome. Active recruitment began in March 2021. HI-PRO will provide clinically meaningful data on whether patients with provoked VTE and enduring risk factors have fewer adverse clinical outcomes if prescribed low-intensity extended duration anticoagulation.

Association between VEGFA gene polymorphisms and bleeding complications in patients maintaining therapeutic international normalized ratio

2019 ◽  
Vol 20 (9) ◽  
pp. 659-667 ◽  
Author(s):  
Jeong Yee ◽  
Woorim Kim ◽  
Byung Chul Chang ◽  
Jee Eun Chung ◽  
Kyung Eun Lee ◽  
...  
Keyword(s):  
Gene Polymorphisms ◽  
Bleeding Complication ◽  
Heart Valves ◽  
Warfarin Therapy ◽  
International Normalized Ratio ◽  
Mechanical Heart Valves ◽  
Bleeding Complications ◽  
Wild Type ◽  
Vegfa Gene

Aim: This study was designed to identify the possible effects of VEGFA polymorphisms on the occurrence of bleeding complications in patients with mechanical heart valves who have achieved therapeutic international normalized ratio (INR). Materials & methods: 13 SNPs of VEGFA were analyzed. Uni- and multi-variate analyses were conducted to identify associations between polymorphisms and bleeding complications. Results & conclusion: Patients with the CC genotype of rs35410204 had an approximately tenfold higher bleeding complication than those with the T allele. For rs866236, patients who had wild-type homozygotes showed an approximately 2.9-fold higher bleeding complication than C allele carriers. This study demonstrated that bleeding complications during warfarin therapy are associated with VEGFA polymorphisms in patients with mechanical heart valves.

Sign in / Sign up

Export Citation Format

Share Document