Warfarin Dose Adjustment Research Articles

Effects of Switching Dose, Dose Variation, and Warfarin Interaction on the Incidence of Stroke Recurrence in Stroke Patients with Atrial Fibrillation

Atrial fibrillation (AF) significantly increases the risk of stroke, necessitating anticoagulation therapy. Warfarin, a commonly prescribed anticoagulant regimen, requires careful monitoring to ensure patient safety. This study aimed to assess the impact of dose switching, dose variation, and potential interactions with warfarin on the incidence of stroke recurrence in stroke patients with AF. The study retrospectively analyzed the treatment records of stroke patients with AF in outpatient settings over one year. The subjects comprised 314 patients who received warfarin prescriptions at two Indonesian Hospitals from January 1, 2015, to December 31, 2019. Out of these patients, 50 had recorded data regarding dose adjustments, variations, and interactions. They were divided into two groups: a case group (n=11) with stroke recurrence and a control group (n=39) without recurrence. Statistical analysis, including chi-square tests and odds ratio calculations, revealed that both warfarin dose switching (OR=7.6) and dose variation (OR=6.6) significantly influenced the incidence of stroke recurrence. It implies that inconsistencies or alterations in warfarin dosing substantially elevate the likelihood of experiencing another stroke, potentially due to inadequate anticoagulation leading to clot formation. Interestingly, the analysis of drug interactions did not significantly impact stroke recurrence. In summary, the recurrence of stroke in patients with AF is notably influenced by warfarin dose adjustments and variations rather than drug interactions. This study highlights the critical importance of precise dosing strategies and vigilant monitoring to enhance the efficacy of anticoagulant therapy in this high-risk population.

Effect of genetic factors on the interindividual variability of warfarin dosage requirements in Japanese patients after adjusting for renal function.

Renal function significantly influences the appropriate warfarin dosage. However, studies investigating the impact of genetic factors on warfarin dosage, considering renal function, are limited. This study aimed to assess the role of genetic polymorphisms in VKORC1, CYP2C9, CYP2C19, CYP4F2, GGCX, and APOE in warfarin dosage adjustment considering renal function. A total of 108 outpatients receiving warfarin treatment with controlled prothrombin time-targeted international normalized ratio (1.5-3.0) were included. Patient data, warfarin dosage, and laboratory results were collected from electronic medical records. Each SNP [VKORC1 rs9923231, CYP2C9 rs1057910, CYP4F2 rs2108622, CYP2C19* 2 (rs4244285) and* 3 (rs4986893), GGCX rs699664 and rs12714145, and APOE rs7421] was analyzed. Multiple regression analysis revealed estimated glomerular filtration rate as the most significant factor influencing warfarin dose (p <0.001) (β = -0.445). VKORC1 rs9923231 AA, CYP4F2 rs2108622 CT/TT, GGCX rs12714145 CT/TT, and CYP2C9 rs1057910 AC carriers were associated with warfarin dose (p <0.001, 0.015, 0.020, 0.038 and β = -0.317, 0.191, -0.188, -0.162, respectively); however, other genes showed no significant association. In conclusion, after adjusting for renal function, genetic factors of VKORC1 rs9923231, CYP4F2 rs2108622, GGCX rs12714145, and CYP2C9 rs1057910 were found to contribute to warfarin dosage, having impact in that order. In contrast, the contribution of other genes to warfarin dosage was absent or negligible.

Anticoagulation Bridging in Patients With Left Ventricular Assist Device: A Regional Analysis of HeartMate 3 Recipients.

Advances in left ventricular assist device technologies have led to an improvement in pump hemocompatibility and outcomes. Because of concerns of thromboembolic complications in prior generations of left ventricular assist devices, bridging with parenteral anticoagulants was routinely. Management strategies of subtherapeutic INRs and their effects on the current generation of devices deserve review. We performed analysis of the MOMENTUM 3 trial including 6 centers in the mid-America region. Patients with subtherapeutic INRs (INR < 2) occurring after the index admission underwent chart review to determine the management strategies taken by clinicians. Strategies were divided into two groups, bridging or nonbridging. Of the 225 patients included in the analysis, 130 (58%) patients had a total of 235 subtherapeutic international normalized ratio (INR) events. Most (n = 179, 76.2%) of these INRs were not bridged (n = 100 warfarin dose adjustment, n = 79 no change in warfarin dose). Among those INRs (n = 56, 23.8%) treated with bridging, approximately half (n = 30, 53.6%) were treated with subcutaneous agents and other half (n = 26, 46.4%) were treated with intravenous agents. There was no difference in individual outcomes or composite endpoints of death, rehospitalization, CVA, or bleeding events between the groups.

Polymorphism Detection of VKORC1 (Vitamin K Epoxide Reductase Complex, Subunit 1) Gene for Warfarin Dose Adjustment in Egyptian Patients with Budd Chiari and/or Portal Vein Thrombosis: A Single Center Experience

Background Budd–Chiari syndrome is a heterogeneous group of disorders characterized by hepatic venous outflow obstruction at the level of the hepatic venules, the large hepatic veins, the inferior vena cava till its junction with the right atrium. The classic triad of abdominal pain, ascites, and hepatomegaly is observed in the vast majority of patients with Budd-Chiari syndrome, but it is nonspecific. Warfarin was introduced into clinical practice in the 1950s, and has been the most widely prescribed oral anti-coagulant for prevention and treatment of thrombotic diseases despite its significant side effects as (bleeding tendency, drug drug interaction). Vitamin K epoxide reductase complex subunit1 (VKORC1), a membrane protein located in hepatocytes, has an important role in the anabolism of vitamin K, which is essential for blood coagulation. Objectives The aim beyond this study is to evaluate effect of the allelic frequency of the VKORC1 (G1639A) polymorphic genes by real time PCR on response of Egyptian patients with Budd–Chiari syndrome or PVT to Warfarin. Patients and Methods The studied patients were selected from patients presented to Budd chiari study group clinic.tropical medicine department in Ain Shams University hospitals. Within 6 months from july 2020 to December 2020, total number of cases during the study period was 50 cases fulfilling the inclusion criteria Results The mean age of the patients was (32.40 ± 9.69) slightly more common in males. The chronic presentation represented 60% of the patients and the acute represented 32%.The most common cause of budd chiarri syndrome was MTHFRD (52%) followed by FVLM (36%) then Primary ant phospholipid antibody syndrome (26%). Patients with the −1639 promoter polymorphism GG genotype had lower dose requirements, whereas the AG/AA genotypes had higher dose. Conclusion Identifying these polymorphisms in patients prior to starting the therapy may help clinicians choose the appropriate warfarin dose &amp; decrease its adverse effects.

Drug interactions between ALK inhibitors and warfarin with concurrent use of bucolome: a case report

BackgroundAlectinib, crizotinib, and ceritinib, are anaplastic lymphoma kinase-tyrosine kinase inhibitors (ALK-TKIs) that exhibit high protein binding, and their metabolism is associated with the cytochrome P450 (CYP) isoenzymes 2C9 or 3A4. The plasma protein binding rate of warfarin, which is used to prevent and treat venous thromboembolism, is also high. Warfarin is a racemate of S-warfarin and R-warfarin, which are metabolized by CYP2C9 and CYP3A4, respectively. Reports on the drug interactions between each of the above-mentioned ALK-TKIs and warfarin with concurrent use of bucolome are currently lacking.Case presentation.We report a case of a patient receiving warfarin and bucolome, whose international normalized ratio (INR) increased after sequential treatment with alectinib, crizotinib, and ceritinib. The patient was a 61-year-old man with a history of aortic valve regurgitation, who was receiving warfarin treatment following aortic valve replacement. Bucolome, which can enhance the effect of warfarin, was also used simultaneously. The patient was diagnosed with primary lung adenocarcinoma, and ALK rearrangement was detected during second-line chemotherapy. After progression of the disease with chemotherapy, sequential treatment with alectinib, crizotinib, and ceritinib was initiated. Pretreatment INR values were in the therapeutic range (target INR of 2–3) but increased to supratherapeutic levels each time after initiation of alectinib, crizotinib, or ceritinib treatment. Adjustment of warfarin dose or discontinuation of bucolome were necessary to maintain the therapeutic INR range. There were no serious bleeding events or substantial changes in dietary intake.Displacement of plasma protein binding or competitive inhibition of metabolism by alectinib, crizotinib, and ceritinib could increase the plasma concentration of the unbound form of warfarin, resulting in high INR values. In addition, alectinib, crizotinib, and ceritinib might cause displacement of bucolome from plasma proteins, followed by displacement of warfarin or inhibition of warfarin metabolism caused by the unbound form of bucolome.ConclusionsClose monitoring of INR and adjustment of warfarin dosage are needed during treatment with alectinib, crizotinib, or ceritinib in patients who receive warfarin with concurrent use of bucolome.

Anticoagulation Management in Patients Receiving Warfarin at Private Cardiac Centers in Addis Ababa, Ethiopia.

Anticoagulants are the cornerstone therapy for thromboembolism prevention and treatment. Warfarin is the frequently prescribed drug and remains the oral anticoagulant of choice in low- and middle-income countries, including Ethiopia. It is a narrow therapeutic index drug that needs high-quality anticoagulation monitoring with frequent international normalization ratio (INR) testing. The study aimed to assess anticoagulation management with warfarin among adult outpatients at two selected private cardiac centers in Addis Ababa, Ethiopia. A hospital-based retrospective study design that enrolled 374 patients receiving warfarin was employed at two private cardiac centres in Addis Ababa, Ethiopia. The time in the therapeutic range (TTR) was calculated using the Rosendaal method. The data were analyzed using Statistical Package for Social Science version 25. The mean age of the patients was 57 years, and 218 (58.3%) participants were females. Out of 3384 INR tests, 1562 (46.5%) were within the therapeutic range and the mean percentage of TTR was 47.24%. Only 25.67% of the patients spent their TTR ≥ 65%. The present study revealed that dose adjustments were required 1764 times. In non-therapeutic INR values of 1764 that required warfarin dose adjustment, 59.7% of the doses were adjusted. About 262 (70.1%) of co-prescribed medications had interaction with warfarin. Sixty-four patients (17.11%) experienced bleeding events. Anticoagulation management with warfarin was suboptimal in private cardiac Addis Ababa, Ethiopia, private cardiac centers. Warfarin adjustment practice for nontherapeutic INR values was not minimal, and many patients encountered bleeding during their course of therapy.

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

BackgroundThe objective of this study was to evaluate the quality of anticoagulation by the time in therapeutic range (TTR) for patients with 12-week INR follow-up interval.Materials and methodsFrom January 2018 to December 2020, a selective group of patients who underwent mechanical valve replacement and followed up at our anticoagulation clinic for adjustment of warfarin dose were enrolled. The incidences of complications of anticoagulation therapy were reported by linearized rates. TTR was calculated by the Rosendaal linear interpolation method.ResultsTwo hundred and seventy-four patients were eligible for this study. The mean age of these patients was 52.8 ± 12.7 years, and 65.7% (180 cases) of them were females. The mean duration of warfarin therapy was 16.7 ± 28.1 months. A total of 1309 INR values were collected, representing 66789 patient days. In this study, the mean TTR was 63.7% ± 18.6%, weekly doses of warfarin were 20.6 ± 6.0 mg/weekly, and the mean monitoring interval for the patient was 53.6 ± 27.1 days. There were 153 cases in good TTR group (TTR ≥ 60%) and 121 cases in poor TTR group (TTR < 60%). The calculated mean TTR in both groups was 42.6% ± 22.1% and 74.8% ± 10.4%, respectively. Compared with the TTR ≥ 60% group, the TTR < 60% group exhibited a more prevalence of female gender (p = 0.001), atrial fibrillation (p < 0.001), NYHA ≥ III (p < 0.001), and lower preoperative left ventricular ejection fraction (LVEF, p = 0.032). In multivariate analysis, female gender (p = 0.023) and atrial fibrillation (p = 0.011) were associated with TTR < 60%. The incidence of major bleeding and thromboembolic events was 2.7% and 1.1% patient-years, respectively. There was one death which resulted from cerebral hemorrhage. The incidence of death was 0.5% patient-years. The difference in anticoagulation-related complications between the TTR < 60% group and the TTR ≥ 60% group was not statistically significant.ConclusionFor patients with stable international normalized ratio monitoring results who are follow-up at anticoagulation clinics, a 12-week monitoring interval has an acceptable quality of anticoagulation. The female gender and atrial fibrillation were associated with TTR < 60%.

Associated factors and safety of the rapidly achieving first therapeutic target of warfarin in hospitalized patients: a retrospective cohort study.

Warfarin is a commonly used anticoagulant drug in clinical practice. Rapidly achieving the first therapeutic international normalized ratio (INR) of warfarin may reduce the hospital length of stay. However, little research has been carried out to evaluate the influencing factors and the safety of rapidly achieving the first therapeutic INR target of warfarin. To investigate the associated factors and the safety of rapidly achieving the first therapeutic INR target of warfarin. A retrospective cohort study was conducted in inpatients who took warfarin from November 2018 to October 2019. Patients' information was retrieved from medical records. 487 patients were included. The mean achieving first therapeutic target time was 6.0 ± 3.2 days (median, 5.0 days). Age > 65 years, body mass index < 24kg/m2, and initial warfarin dose ≥ 3mg/d were independent factors associated with the rapidly achieving first INR target of warfarin therapy. The incidence of INR ≥ 4 was higher in patients achieving the first INR target rapidly than those achieving the first INR target slowly, while there were no significant differences in bleeding events between the two groups. Hospitalized patients aged > 65 years, with a body mass index < 24kg/m2, or receiving an initial warfarin dose ≥ 3mg/d were more likely to achieve the first INR target of warfarin rapidly. Closer INR monitoring and appropriate warfarin dose adjustment are recommended to improve the safety for patients achieving the first INR ≥ 1.8 within 6 days after beginning oral warfarin.

Association of VKORC1 and CYP2C9 single-nucleotide polymorphisms with warfarin dose adjustment in Saudi patients.

Despite its wide usage, warfarin therapy remains challenging due to its narrow therapeutic index, inter-individual response variability, and risk of bleeding. Previous reports have suggested that polymorphisms in VKORC1 and CYP2C9 genes could influence warfarin therapy. Herein, we investigated whether VKORC1-1173C>T, CYP2C9*2, and CYP2C9*3 gene polymorphisms are associated with warfarin dose adjustment and related bleeding events. This cross-sectional study was conducted on Saudi adults receiving warfarin for more than 1month. Their demographics and relevant clinical data were obtained. Genotyping for VKORC1-1173C>T, CYP2C9*2, and CYP2C9*2 genotypes was performed. Patients who are homozygous for the mutant T allele VKORC1 T/T required the lowest warfarin daily maintenance dose, compared to VKORC1 C/T and VKORC1 C/C. Similarly, there was a significant reduction in warfarin daily maintenance dose among CYP2C9*1/*3 and CYP2C9*1/*2 groups compared to CYP2C9*1/*1. However, we found no significant correlation between the studied polymorphisms and warfarin-associated bleeding. Similar to other populations, the VKORC1 and CYP2C9 gene polymorphisms are significantly associated with warfarin dosage in Saudi patients. The presence of at least one copy of the mutant alleles for VKORC1-1173C>T, CYP2C9*2, and CYP2C9*3 is associated with a significant reduction in warfarin maintenance dose.

Association of VKORC1 and CYP2C9 single-nucleotide polymorphisms with warfarin dose adjustment in Saudi patients.

Despite its wide usage, warfarin therapy remains challenging due to its narrow therapeutic index, inter-individual response variability, and risk of bleeding. Previous reports have suggested that polymorphisms in VKORC1 and CYP2C9 genes could influence warfarin therapy. Herein, we investigated whether VKORC1-1173C>T, CYP2C9*2, and CYP2C9*3 gene polymorphisms are associated with warfarin dose adjustment and related bleeding events. This cross-sectional study was conducted on Saudi adults receiving warfarin for more than 1month. Their demographics and relevant clinical data were obtained. Genotyping for VKORC1-1173C>T, CYP2C9*2, and CYP2C9*2 genotypes was performed. Patients who are homozygous for the mutant T allele VKORC1 T/T required the lowest warfarin daily maintenance dose, compared to VKORC1 C/T and VKORC1 C/C. Similarly, there was a significant reduction in warfarin daily maintenance dose among CYP2C9*1/*3 and CYP2C9*1/*2 groups compared to CYP2C9*1/*1. However, we found no significant correlation between the studied polymorphisms and warfarin-associated bleeding. Similar to other populations, the VKORC1 and CYP2C9 gene polymorphisms are significantly associated with warfarin dosage in Saudi patients. The presence of at least one copy of the mutant alleles for VKORC1-1173C>T, CYP2C9*2, and CYP2C9*3 is associated with a significant reduction in warfarin maintenance dose.

Does ramadan fasting affect the therapeutic and clinical outcomes of warfarin? a systematic review and meta-analysis.

Warfarin's therapeutic effect is affected by many factors, including diet modifications. The impact of Ramadan fasting on warfarin is controversial. The aim of this systematic review and meta-analysis was to investigate the effect of Ramadan fasting on patients taking warfarin. A literature search was done in PubMed, WOS, Scopus, and Embase from inception to May 24, 2021. All relevant studies measuring the international normalized ratio (INR), time in therapeutic range (TTR), or the number of patients within therapeutic range before, during, and after Ramadan were assessed by full-text screening for achieving all of the inclusion criteria. We used the Newcastle-Ottawa Scale for quality assessment and RevMan 5.4 software for meta-analysis. A total of five studies with 446 patients were included in the meta-analysis. The patients served as their own control. Our pooled analyses showed no significant difference during Ramadan compared to pre-Ramadan (MD: 0.08; 95% CI: - 0.00, 0.15; P = 0.06) and post-Ramadan (MD: - 0.00; 95% CI: - 0.14, 0.14; P = 1.00, respectively). There was only a significant increase in the risk ratio of supratherapeutic INR when comparing post-Ramadan vs. pre-Ramadan (RR: 1.69; 95% CI: 1.22, 2.33; P = 0.001). However, there was no significant risk for supratherapeutic INR during Ramadan compared to pre-Ramadan or post-Ramadan; the number of patients within the therapeutic range of INR during Ramadan compared to pre-Ramadan; and TTR during Ramadan, pre-Ramadan, and post-Ramadan. Ramadan fasting did not affect INR level, TTR, or the number of patients within the therapeutic range before, during, and after Ramadan. However, there was a possibility of achieving a supratherapeutic INR post-Ramadan compared to pre-Ramadan. Therefore, INR monitoring and warfarin dose adjustments accordingly are recommended after Ramadan.

A smartphone application for remote adjustment of warfarin dose: Development and usability study

AimThe aim of this article is (a) to design and develop a smartphone app called Alfalfa that can provide remote dose adjustment (b) to evaluate its usability. BackgroundPatients taking warfarin need to spend substantial time, money, and energy frequently visiting the hospital in order to adjust its dose. Internet technology may be able to provide convenient dose adjustment services for these patients. MethodsWe thought and discussed repeatedly about how to ensure the safety and effectiveness of remote administration of warfarin, and finally designed and developed the Alfalfa app. In addition, patients and medical practitioners were invited to participate in a system usability scale (SUS) to assess the usability of Alfalfa. ResultsAs of July 5, 2021, the number of Alfalfa accounts was 1736, including 1624 patients and 112 medical staff, and it provided a total of 12,968 remote dose adjustments. A total of 26 people participated in the questionnaire, including 15 patients and 11 medical staff. The results of SUS show that the usability score of patient terminal and medical terminal is 61.8 and 82.7, respectively. And age does not affect the usability of patient terminal. The usability of the Alfalfa app was rated similarly by younger and older adults (63.5 vs. 58.5, P = .535). ConclusionsThis study proves that the Alfalfa app can be used for remote management of warfarin. The usability of medical terminal is acceptable to medical practitioners, while the usability of patient terminal needs further improvement. Trial registrationChiCTR1900021920.

Performance Evaluation of Warfarin Dose Prediction Algorithms and Effects of Clinical Factors on Warfarin Dose in Chinese Patients.

The clinical utility of warfarin dose prediction algorithms remains controversial, our purpose is to evaluate the performance of warfarin dose prediction algorithms and the effects of clinical factors on warfarin dose in Chinese patients. Clinical data of 217 patients who received warfarin treatment were used to assess 6 warfarin dose prediction algorithms (OHNO, IWPC [International Warfarin Pharmacogenetics Consortium], HUANG, KIM, BRESS, and MIAO). The predicted dose (PD) was compared with the warfarin optimal dose (WOD, defined as the dose that maintains the international normalized ratio within the target range of 2.0-3.0). A multiple regression analysis with WOD as the dependent variable was performed to evaluate the effects of clinical factors on warfarin dose. The mean absolute error analysis ranked the predictive accuracies of the algorithms as OHNO > IWPC > HUANG > KIM > BRESS > MIAO. Stratified analysis indicated that HUANG most accurately predicted that patients required lower WODs (≤3 mg/d), whereas OHNO was the most effective in predicting medium WODs (3-5 mg/d). KIM was effective in predicting high WODs (>5 mg/d). Multiple linear regression analysis showed that VKORC1 (rs9923231) and body mass index were significantly positively correlated with WOD, whereas concurrent atrial fibrillation status, CYP2C9*3 (rs1057910), and sex were significantly negatively correlated with WOD. In Chinese patients, OHNO should be given priority during the prediction and selection of warfarin dose. When using OHNO to predict warfarin dose (≤3 mg/d or >5 mg/d), HUANG or KIM algorithms can provide precise predictions. At the same time, physicians should pay close attention to clinical factors, such as VKORC1 (rs9923231), concurrent atrial fibrillation status, CYP2C9*3 (rs1057910), body mass index, and sex, to improve warfarin dose adjustment strategies in Chinese patients.

From a DOAC to Warfarin: Reasons Why Patients Switch

1. IntroductionThe introduction of direct oral anticoagulants (DOACs) has led to their widespread use for stroke prevention in patients with non-valvular atrial fibrillation (AF) and as first-line treatment in acute venous thromboembolism (VTE), and also as secondary thromboprophylaxis in patients with a history of VTE. In addition, many patients previously taking vitamin K antagonists (VKAs) have switched to a DOAC for reasons including erratic international normalised ratio (INR) control, medication interactions, convenience, possible lower major bleeding risk and possible improved stroke prevention rates. Although DOACs are well tolerated, little is known about the numbers of patients switching from a DOAC to (or back to) a VKA or the reasons for doing so.2. MethodsThis study was an analysis of prospectively-collected data from a four-year period surveying a computer-based VKA (warfarin) dose adjustment clinic in a large city centre hospital. The primary objective was to identify the reasons for patients switching from a DOAC to warfarin. Secondary objectives included assessing indication for anticoagulant therapy and choice of DOAC. The time in therapeutic range (TTR) once switched back to VKA and clinical events following commencement of warfarin were also determined.3. ResultsIn our VKA clinic with 1791 patients annually under review, 39 patients were identified as having switched from a DOAC to warfarin. The mean age of the patients was 68.5 years +/- 13.8 and the majority (N=24) were female. AF was the most common condition necessitating anticoagulation (N=24); VTE accounted for 12 cases; arterial thromboembolism (N=2) and cardiac thrombus (N=1) were less common causes and one patient had been started on a DOAC in the setting of valvular replacement. Of the patients who were switched to warfarin, seven (17.9%) had originally been anticoagulated with a VKA prior commencing on a DOAC. In terms of anticoagulant choice, the majority of patients (N = 27) were taking rivaroxaban with 6 patients each on dabigatran and apixaban. The causes for switching in this cohort are outlined in table 1. Interesting cases of note include one patient who had a splenic infarction while taking rivaroxaban for atrial fibrillation and one patient who developed a new thumb arterial embolus while taking rivaroxaban for a PE.Following warfarin commencement, there was a total of eight clinical events reported (21.1% of patients). There were seven bleeding events recorded with two serious events necessitating hospital admission and five minor events; in five of these (71.4%), the original reason for switching back to warfarin had been a bleed while on a DOAC. One further patient had a high INR necessitating administration of vitamin K. The mean TTR of this cohort was 61.4% +/- 22.3. 33 patients (84.6%) of patients still attend the warfarin clinic, with cessation of anticoagulant therapy having occurred in three patients (7.7%) and death occurring in one patient (2.6%); two patients (5.1%) have been recommenced on a DOAC.4. DiscussionDOACs have several advantages over warfarin for many patients; they do not require monitoring and the dose remains stable. Index trials have demonstrated at least non-inferiority to warfarin in stroke prevention in non-valvular AF and treatment of VTE, with at least no significant difference in bleeding outcomes. However, warfarin can be an attractive option in complicated cases as it can be rapidly reversed, and there continues to be greater levels of clinician experience with its use. In the present study, we report data regarding the switch back to warfarin in a DOAC cohort, an area into which little research has been conducted. There were only 39 patients reported over a four-year period; this represents only a small minority of the full cohort. As expected, the majority of patients required a switch because of re-thrombosis or a bleeding event. Patients also required an appropriate switch in situations outside of the licence of the DOACs i.e. renal deterioration or valvular AF. The authors are not aware of any data regarding arterial embolisation in rivaroxaban users, and acute hepatitis has been rarely described in rivaroxaban use. These data confirm that switching from a DOAC to warfarin is seldom deemed necessary by clinicians. However, familiarity and experience may guide therapy in complicated cases, and vigilance is required to ensure adherence to the licence when prescribing a DOAC. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Safety of warfarin therapy in children with coronary aneurysm due to Kawasaki disease

Objective: To investigate the safety of warfarin for Kawasaki disease (KD) with coronary artery aneurysm (CAA) and its prognosis. Methods: Twenty one children with KD complicated with giant CAA, multiple CAA in one coronary artery or thrombosis in coronary artery were enrolled in this prospective study. Warfarin was used to control the goal international normalized ratio (INR) ranging from 2.0 to 3.0. The CAA diameter, number, location and thrombus in coronary artery were recorded at the beginning of treatment, 1, 2, 3, 4 weeks and 2, 3, 6, 12 months after treatment, as well as the influence on INR, electrocaroliogram, creatine kinase-MB (CK-MB), troponin I. Standardized warfarin bleeding risk training and management was implemented. Children were divided into implementation group and non-implementation group according to the status of actual implementation of their parents. The incidence of bleeding events was compared between the two groups. Comparisons between groups were performed using a Rank sum test and a Fisher exact test. Results: In the 21 patients (15 males and 6 females), the age of onset ranged from 2 months to 6 years. There were 4 cases with grade Ⅱ, 7 cases with grade Ⅲ, 7 cases with grade Ⅳ and 3 cases with grade Ⅴ according to the severity of coronary arterial lesions before treatment. The time of clinical detection of thrombus in 10 children with thrombosis ranged from the fourth day to the fourth month. The dose distribution of warfarin was 0.06-0.10 mg/(kg·d), and the INR was 1.80-2.59. Among the 10 cases with thrombus, 8 cases had disappearance of thrombi and 2 cases with grade Ⅴ had thrombus organization to different degree. After treatment, the coronary artery ectasia of the 4 cases with grade Ⅱ all returned to normal. Among the 7 cases with grade Ⅲ, 3 cases of coronary artery aneurysms returned to normal, and 4 cases did not change. Among the 7 cases with grade Ⅳ , 5 cases of coronary artery aneurysms shrank to grade Ⅲ, and 2 cases remained unchanged. Three cases with grade Ⅴ lesions had no changes in aneurysm. Neither new thrombus nor new CAA was detected during the treatment. There was no significant change in electrocardiogram before and after treatment. No statistically significant difference was found regarding the troponin I (0.07 (0-3.01) vs. 0.04 (0-0.29) μg/L, Z=0.932, P>0.05) and CK-MB (20.6 (11.2-58.2) vs. 29.0 (16.7-47.0) U/L, Z=1.906, P>0.05) before and after treatment. The incidence of bleeding events in the implementation group was significantly lower than that in the non-implementation group (2/15 vs. 4/6, Fisher=5.689, P=0.031). Conclusions: The application of goal INR of 2.0-3.0 and adjustment of warfarin dose according to the severity of CAA combined with standardized and strict warfarin bleeding risk training and management, can increase the safety of warfarin therapy in children with KD, improve the prognosis of coronary artery lesions, promote the dissolution of thrombi, prevent new thrombosis, and effectively reduce the incidence of bleeding complication.

A physiologically based pharmacokinetic/pharmacodynamic modeling approach for drug-drug interaction evaluation of warfarin enantiomers with sorafenib

Sorafenib was suggested to cause drug-drug interaction (DDI) with the common anticoagulant, warfarin based on published studies. The inhibition on CYP2C9 enzyme was thought to be the mechanism, but further studies are warranted. Thus, a mechanistic PBPK/PD model for warfarin enantiomers was developed to predict DDI potential with sorafenib, aiming at providing reference for the rational use of both drugs.PBPK models of warfarin enantiomers were constructed by Simcyp software. A mechanistic PK/PD model was built in NONMEM software. PBPK model of sorafenib was fitted via a top-down method. The final PBPK/PD model of warfarin enantiomers was verified and validated by different dosing regimens, ethnicities and genetic polymorphisms, and used to perform DDI simulations between warfarin racemate and sorafenib among general populations and sub-populations with various CYP2C9 and VKORC1 genotypes. Results suggested low DDI risk between warfarin and sorafenib for general populations. Potentially serious consequence was seen for those carrying both CYP2C9 ∗2 and ∗3 and VKORC1 A/A genotypes.This PBPK/PD modeling approach for warfarin enantiomers enabled DDI evaluation with sorafenib. Close monitoring and warfarin dosage adjustment were recommended for patients carrying mutant genotypes. The novel model could be applied to investigate other drugs that may interact with warfarin.

Adjustment of Warfarin Dose after Bariatric Surgery in Patients on Long-Term Anticoagulants: A Single Institution Experience

Adjustment of Warfarin Dose after Bariatric Surgery in Patients on Long-Term Anticoagulants: A Single Institution Experience

Efficacy of Point-of-Care for INR Testing Compared to Standard Laboratory Methods at a Tertiary Care Hospital in Saudi Arabia.

Regular testing of the international normalized ratio (INR) is essential for people taking vitamin K antagonists as part of anticoagulation therapy. This study was undertaken to ascertain the efficacy of point-of-care testing (POCT)-INR versus conventional core laboratory testing in terms of result adequacy, waiting-time reduction, and patient satisfaction enhancement at the thrombosis clinic of the outpatient Medical Specialties Department in King Fahad Medical City, Saudi Arabia. The study was conducted prospectively for 6 months (from June 2017 to December 2017) on 182 eligible participants out of 250 entitled patients who were attending the thrombosis clinic for warfarin dose adjustment and who fulfilled all the prerequisites for performing dual testing by fingerstick at the clinic and venipuncture by the core laboratory. The data-capturing template created on Microsoft Excel recorded turnaround times (TATs), clinical concordance of INR result variables by POCT, and laboratory methods. Individual patient experience was recorded to gauge satisfaction rate, and all the data were analyzed statistically. Of 182 patients included in the study, overall good concord was observed between POCT whole blood and laboratory plasma INR results with median bias of 0.07 and 92.3% agreement using acceptability criteria for clinical concordance of Clinical Laboratory Standards Institute (CLSI) 14-A and International Standards Organization (ISO) 17593-2007, respectively. Marked improvement in terms of patient's time spent at the clinic was noted, with substantial reduction from 180 to ∼30 minutes (p < 0.001). Survey questionnaire responses indicated that POCT of INR was highly convenient and enhanced patient experience in terms of shorter wait time, minimal invasive procedures, and immediate result availability (p < 0.001). Predominantly, participants (75.4%) endorsed and expressed a strong preference for the POCT procedure over conventional laboratory testing. Whole blood INR testing for warfarin dose adjustment with validated POCT devices is adequately comparable to the core laboratory results. It also simplifies workflow steps at the thrombosis clinic, enhancing patient experience and convenience via the immediate availability of results, a less invasive procedure, and a marked reduction in waiting time. However, caution is needed with regard to higher INR results (≥4.7), which call for core laboratory confirmation.

The Magnitude of the Warfarin‐Amiodarone Drug‐Drug Interaction Varies With Renal Function: A Propensity‐Matched Cohort Study

Amiodarone inhibits warfarin metabolism and is associated with major bleeding during warfarin therapy. Managing this drug-drug interaction (DDI) is challenging because of substantial interpatient variability in DDI magnitude. Because renal dysfunction induces changes in drug metabolism and protein binding that could alter cytochrome P450 inhibition mechanisms, we hypothesized that renal dysfunction alters the impact of the warfarin-amiodarone DDI. We tested this question in a propensity-matched cohort study of hospitalized patients with atrial fibrillation. Patients were queried from an electronic health record database. Renal function was estimated with creatinine clearance (CrCl). Warfarin response was measured with the warfarin sensitivity index (WSI), a dose-normalized international normalized ratio (INR) measure, and was modeled with multilevel mixed-effects linear regression. Time to supratherapeutic INR (>4) was modeled using Cox regression. Propensity score matching resulted in 4,518 patients administered amiodarone and 4,518 controls. Amiodarone's effect on warfarin response varied threefold across the renal function range, increasing WSI by 36% in patients with normal renal function (CrCl 115mL/minute), but by only 11.8% in patients with severe renal dysfunction (CrCl 15mL/minute). Similarly, amiodarone had a strong effect in patients with normal renal function (hazard ratio (HR) 1.80; 1.23, 2.64), but a negligible effect on supratherapeutic INR hazard in patients with severe renal dysfunction (HR 1.01; 0.75, 1.37). These results suggest that renal function is a novel factor that explains substantial variability in the warfarin-amiodarone DDI. This information could inform warfarin dosage adjustment and monitoring and may have implications for the selection of oral anticoagulation agents in patients treated with amiodarone.

A cross-sectional evaluation of five warfarin anticoagulation services in Uganda and South Africa.

Warfarin is the most commonly prescribed oral anticoagulant in sub-Saharan Africa and requires ongoing monitoring. The burden of both infectious diseases and non-communicable diseases is high and medicines used to treat comorbidities may interact with warfarin. We describe service provision, patient characteristics, and anticoagulation control at selected anticoagulation clinics in Uganda and South Africa. We evaluated two outpatient anticoagulation services in Kampala, Uganda and three in Cape Town, South Africa between 1 January and 31 July 2018. We collected information from key staff members about the clinics' service provision and extracted demographic and clinical data from a sample of patients' clinic records. We calculated time in therapeutic range (TTR) over the most recent 3-month period using the Rosendaal interpolation method. We included three tertiary level, one secondary level and one primary level anticoagulation service, seeing between 30 and 800 patients per month. Care was rendered by nurses, medical officers, and specialists. All healthcare facilities had on-site pharmacies; laboratory INR testing was off-site at two. Three clinics used warfarin dose-adjustment protocols; these were not validated for local use. We reviewed 229 patient clinical records. Most common indications for warfarin were venous thrombo-embolism in 112/229 (49%), atrial fibrillation in 74/229 (32%) and valvular heart disease in 30/229 (13%). Patients were generally followed up monthly. HIV prevalence was 20% and 5% at Ugandan and South African clinics respectively. Cardiovascular comorbidity predominated. Furosemide, paracetamol, enalapril, simvastatin, and tramadol were the most common concomitant drugs. Anticoagulation control was poor at all included clinics with median TTR of 41% (interquartile range 14% to 69%). TTR was suboptimal at all included sites, despite frequent patient follow-up. Strategies to improve INR control in sub-Saharan patients taking warfarin are needed. Locally validated warfarin dosing algorithms in Uganda and South Africa may improve INR control.