Warfarin Therapy in the HIV Medical Home Model: Low Rates of Therapeutic Anticoagulation Despite Adherence and Differences in Dosing Based on Specific Antiretrovirals

Abstract To determine the indications for, rates of therapeutic anticoagulation during, and complications of warfarin therapy in HIV-infected individuals, in whom long-term anticoagulation is frequently indicated. To identify risk factors for nonoptimal anticoagulation and to determine if warfarin dosing is differentially affected by specific antiretroviral agents. Retrospective study of a dedicated anticoagulation program at one of the largest clinics for HIV-infected individuals in the United States. Seventy-three HIV-infected individuals on warfarin were followed for a total of 911 visits. The rate of therapeutic internation normalized ratio (INR) levels was 34.5% when including only visits at which patients were assessed to be adherent with warfarin. In multivariable analysis, injection drug use at baseline was an independent risk factor for subtherapeutic INR (odds ratio [OR] 2.4, 95% confidence interval [CI] 1.3-4.7, p=0.01). Additionally, warfarin adherence was protective of both subtherapeutic (OR 0.4, 95% CI 0.2-0.6, p<0.0001) and supratherapeutic (OR 0.5, 95% CI 0.3-0.9, p=0.02) INR status. Efavirenz-based antiretroviral regimens were associated with lower weekly warfarin doses (46?mg) to maintain therapeutic INR compared to lopinavir/ritonavir-based regimens (68?mg; p=0.01) and atazanavir/ritonavir-based regimens (71?mg; p=0.007). Consistently therapeutic warfarin therapy is difficult to achieve in HIV-infected individuals, even with a dedicated anticoagulation program. Adherence to warfarin therapy is important but rates of therapeutic INR levels are nonetheless low. Lower warfarin dosing was required for efavirenz compared to two commonly used protease inhibitor-based regimens. Because of these factors, the emergence of new oral anticoagulants is an important development for HIV-infected individuals who require long term anticoagulation therapy.     

Cotreatment with lenvatinib and warfarin potassium caused prothrombin time prolongation

Lenvatinib is approved as a standard systemic therapy for unresectable hepatocellular carcinoma (HCC) patients; however, experience with lenvatinib in clinical practice is insufficient. We present the case of a patient with advanced HCC whose prothrombin time – international normalized ratio (PT‐INR) was elevated after cotreatment with lenvatinib and warfarin potassium. The patient was a 26‐year‐old man with congenital abnormalities who had to take warfarin potassium because he had a mechanical heart valve. He was diagnosed with unresectable HCC at 24 years old and was treated by transcatheter arterial chemoembolization and transcatheter arterial infusion. After some interventional radiology treatments, lenvatinib was started. After 4 days of treatment with lenvatinib and warfarin potassium, his PT‐INR increased to 4.13, and the treatment had to be stopped. No changes were observed in other Child–Pugh score factors. The elevation in the PT‐INR after cotreatment with lenvatinib and warfarin potassium was thought to be caused by pharmacological effects of concurrent use or pharmacological sensitivity to warfarin potassium in this patient with liver dysfunction. The PT‐INR must be monitored when lenvatinib is given to advanced HCC patients taking warfarin potassium.     

Initiation of warfarin therapy in elderly medical inpatients: a safe and accurate regimen

PURPOSE: Elderly patients are at high risk of over-anticoagulation when treated with warfarin, especially during treatment induction. We developed a simple low-dose regimen for starting warfarin therapy in elderly inpatients. The daily maintenance dosage is predicted from the international normalized ratio (INR) measured the day after the third daily intake of a 4-mg dose. We conducted a prospective multicenter study to evaluate the accuracy and safety of this regimen. METHODS: We studied 106 elderly (age >or=70 years) inpatients (mean [+/- SD] age, 85 +/- 6 years; range, 71 to 97 years) who had a target INR of 2.0 to 3.0. Accuracy in predicting the daily maintenance dose from INR value on day 3 was evaluated. RESULTS: The predicted daily maintenance warfarin dose (3.1 +/- 1.6 mg/d) correlated closely with the actual maintenance dose (3.2 +/- 1.7 mg/d; R(2) = 0.84). The predicted dose was equal to the actual dose in 77 patients (73%; 95% confidence interval [CI]: 64% to 81%) and within 1 mg in 101 patients (95%; 95% CI: 91% to 99%). The mean time needed to achieve a therapeutic INR was 6.7 +/- 3.3 days (median, 6.0 days); the mean time needed to achieve the maintenance dose was 9.2 +/- 4.5 days (median, 7.0 days). None of the patients had an INR >4.0 during this period. One fatal bleeding event was recorded in a patient with an INR in the therapeutic range. CONCLUSION: Our warfarin induction regimen was simple, safe, and accurate in predicting the daily maintenance warfarin dose in elderly hospitalized patients.     

Clinical predictors of prolonged delay in return of the international normalized ratio to within the therapeutic range after excessive anticoagulation with warfarin

BACKGROUND: An elevated international normalized ratio (INR) increases the risk for major hemorrhage during warfarin therapy. Optimal management of patients with asymptomatic elevations in INR is hampered by the lack of understanding of the time course of INR decay after cessation of warfarin therapy. OBJECTIVE: To identify predictors of the rate of INR normalization after excessive anticoagulation. DESIGN: Retrospective cohort study. SETTING: Outpatient anticoagulant therapy unit. PATIENTS: Outpatients with an INR greater than 6.0 were identified from August 1993 to September 1998. Patients in whom two doses of warfarin were withheld and a follow-up INR was obtained on the second calendar day were enrolled. No patient received vitamin K(1). MEASUREMENTS: The INR was measured 2 days after an INR greater than 6.0 was recorded. RESULTS: Of 633 study patients with an initial INR greater than 6.0, 232 (37%) still had an INR of 4.0 or greater after two doses of warfarin were withheld. Patients who required larger weekly maintenance doses of warfarin were less likely to have an INR of 4.0 or greater on day 2 (adjusted odds ratio per 10 mg of warfarin, 0.87 [95% CI, 0.79 to 0.97]). Other risk factors for having an INR of 4.0 or greater on day 2 included age (odds ratio per decade of life, 1.18 [CI, 1.01 to 1.38]), index INR (odds ratio per unit, 1.25 [CI, 1.14 to 1.37]), decompensated congestive heart failure (odds ratio, 2.79 [CI, 1.30 to 5.98]), and active cancer (odds ratio, 2.48 [CI, 1.11 to 5.57]). CONCLUSIONS: Steady-state warfarin dose, advanced age, and extreme elevation in INR are risk factors for prolonged delay in return of the INR to within the therapeutic range. Decompensated congestive heart failure and active cancer greatly increase this risk.     

"The end of good luck'--long-term survival without anticoagulation: a case report and review of the literature

Long-term anticoagulation in patients with metallic prosthetic valve disease is required according to current guidelines. We describe a patient with a functioning mitral mechanical valve without anticoagulation for 27 years. A 46-year-old man admitted to the emergency department with complains of palpitation. The patient had a mitral valve replacement because of severe mitral stenosis. He discontinued warfarin treatment 1 month after surgery because of the unavailability of this drug in Turkey. Transthoracic echocardiography revealed functioning metalic mitral valve with a mean gradient of 9 mm Hg. Fluoroscopy showed normal excursions of the mechanical mitral valve. Transesophageal echocardiography was performed and revealed fresh thrombus formation in the left atrial appendix. Admission international normalized ration (INR) level was 1.79. Due to the higher INR level and long-term survival, genetic analysis of warfarin polymorphism was performed. There was a homozygous mutation in the vitamin K epoxide reductase complex 1 (VKORC1) 1173C>T and 1639G>A genotypes. The possible explanations of long-term survival and baseline higher INR level were linked to the mutation in warfarin metabolism. We also briefly review the literature.     

Monitoring Therapy with Vitamin K Antagonists in Patients with Lupus Anticoagulant: Effect on Different Tests for INR Determination

Background: Lupus anticoagulant (antiphospholipid antibodies) is associated with venous and arterial thrombosis in patients with and without autoimmune disorders. Vitamin K antagonists are the treatment of choice in patients with thrombosis, of which the dose is titrated by INR monitoring. Several recent reports suggest that the presence of the lupus anticoagulant disturbs the INR test and may lead to unreliable results with a large variation in INR values, dependent on the reagents used.Methods: We studied 11 lupus anticoagulant positive patients and 11 lupus anticoagulant negative patients, all using vitamin K antagonists. The INR value was determined using seven different tests and the variation in INR values was compared between the two groups. The amidolytic Factor X levels were used as an phospholipid independent measure for intensity of warfarin therapy. Factor VII and X activity were measured to assess the stability of warfarin therapy.Results: The variation of the results with different INR tests within one patient was minimal and comparable in the two groups for INR's in the therapeutic range. The coefficient of variation for the cases and control group was 10.43 and 9.35, respectively. Variation in both groups increased at supratherapeutic levels of anticoagulation and when the anticoagulation was unstable (measured with Factor X/Factor VII ratio). The relationship between INR values and Factor X analysis revealed no influence of the lupus anticoagulant.Conclusions: In this study, lupus anticoagulant antibodies do not disturb INR laboratory tests. Differences in INR measurements are seen in patients with a high intensity of anticoagulation and in patients who either just started or in whom no stable anticoagulation has been achieved.Abbreviated Abstract. This study investigates the influence of lupus anticoagulant on INR determination tests in patients treated with warfarin. Eleven cases and eleven lupus anticoagulant negative control patients, also on warfarin therapy, were included. Seven INR results per patient were obtained using different laboratory tests. A factor X assay was performed to obtain an independent measure for the intensity of warfarin therapy.The variation of INR results between the cases and controls revealed no difference in these groups. In addition, the relationship between INR values and Factor X analysis indicated no influence of the lupus anticoagulant. What was observed was an increased difference in INR values in patients with a high intensity of anticoagulation and in patients who either just started or in whom no stable anticoagulation has been achieved     

A retrospective analysis of the periprocedural management of oral anticoagulants in patients undergoing interventional radiology procedures

Limited evidence is available to guide periprocedural management of oral anticoagulants in the setting of interventional radiology (IR) procedures. For direct oral anticoagulants, therapy interruption (TI) is based on medication half-life and procedural bleeding risk. Periprocedural management of warfarin includes INR monitoring, and possible bridging with parenteral anticoagulants. It is unknown if these recommendations apply to IR procedures. To evaluate bleeding complications and thromboembolic events following periprocedural management of the factor Xa (FXa) inhibitors or warfarin in patients undergoing IR procedures. We performed a retrospective, observational study at NYU Langone Health (NYULH) of all adult patients who underwent an IR procedure from January 2015 to July 2017 and were receiving apixaban, rivaroxaban, or warfarin. Patients who were pregnant or who had a mechanical heart valve were excluded. At NYULH, TI is not required for FXa inhibitors, and an INR?<?3 is recommended for patients on warfarin undergoing low risk procedures. For moderate/high risk procedures, TI for 48 h or 72 h with reduced renal function, is recommended for FXa inhibitors, and an INR?<?1.5 is recommended for patients on warfarin. We evaluated 350 IR procedures, with a total of 174 low bleeding risk and 176 moderate/high bleeding risk. The 30-day major bleeding rate was 0.9%, clinically relevant non-major bleeding rate was 3%, minor bleeding rate was 1% and thromboembolic event rate was 1%. The periprocedural oral anticoagulation management strategy at NYULH appears safe given the low 30-day incidence of bleeding and thromboembolic events.     

Improving the safety profile of warfarin

Since warfarin remains the predominate drug administered for long-term anticoagulation, optimizing therapy for maximum antithrombotic effect with minimal bleeding risk continues to challenge clinicians. Genetic differences exist that affect an individual's response to warfarin. The clinician can use genetic information in the future, along with current approaches to improved monitoring and dose schedules, to maintain even more successfully the appropriate therapeutic range for anticoagulation. The international normalized ratio (INR) is a good indicator of warfarin effect and addressing a high INR result often prevents bleeding complications. However, even with a therapeutic INR, patients are still at risk for bleeding. This review will discuss optimizing warfarin dosing, reducing an elevated INR, and managing the anticoagulated patient who has a bleeding event.     

Safe introduction of warfarin for thrombotic prophylaxis in atrial fibrillation requiring only a weekly INR

A new protocol for initiating warfarin therapy was introduced to reduce the workload in the Anticoagulant Clinic. A total of 200 outpatients, with a median age of 74 years, requiring anticoagulation for atrial fibrillation, commenced warfarin 3 mg daily for 1 week. Patients were initially seen weekly, and subsequent warfarin doses were dictated by the International Normalized Ratio (INR) on days 8 and 15; 84% of patients followed the protocol correctly: of these 86% had an INR > or =2 by day 15 and >98% had INR >2 by day 22. By day 22, 58% of patients achieved a stable dose, 85% by day 29 and >95% by day 36. Day 8 INR was predictive of the final maintenance dose required. No patient suffered any thrombotic or haemorrhagic complications in the first month: only three patients had an INR >3 on day 8, and 11 patients had an INR >4 on day 15. Patient age and sex were not sufficiently related to warfarin requirement to provide useful predictive information. This protocol, requiring only weekly INRs, has proved safe and effective for outpatient warfarinization, and has reduced clinic attendances in this population.     

Triple Antithrombotic Therapy in Patients With Left Ventricular Assist Devices

Data on the efficacy and safety of the combination of warfarin and dual-antiplatelet therapy compared with warfarin and mono-antiplatelet therapy (MAPT) in patients with left ventricular assist devices (LVAD) remains scarce. Single-center study of 130 consecutive patients with durable LVAD. Baseline demographics, antithrombotic and antiplatelet regimen, and outcomes were compared between patients receiving warfarin plus dual-antiplatelet therapy (Group 1) and warfarin plus MAPT (Group 2). Antiplatelet therapy was assessed at hospital discharge post-LVAD implant and included aspirin, clopidogrel and dipyridamole. Outcomes at 1-year were assessed in each group. All patients were on aspirin and warfarin. No significant differences with regards to age, gender or ethnicity were noted at baseline between the two groups. Group 1 was more likely to have higher lactate dehydrogenase LDH levels at discharge and a history of stroke. No significant differences in international normalized ratio INR, hemoglobin or hematocrit were noted at discharge. During the study period, 48 patients had gastrointestinal bleeding events: 28 of 68 (41.2%) in Group 1 vs 20 of 62 (32.2%) in Group 2 (P = 0.293). At 1year, no statistically significant differences were noted in gastrointestinal bleeding (Group 1=27.90% vs Group 2 = 25.80, P = 0.784), ischemic stroke (Group 1 = 8.8% vs group 2 = 6.5%, P = 0.612), hemorrhagic stroke (Group 1 = 4.4% vs group 2 = 3.2%, P = 0.725) or mortality (Group 1 = 5.9% vs Group 2 = 1.6%, P = 0.206). Rates of pump thrombosis however were lower in Group 1 (Group 1 = 0% vs Group 2 = 6.5%, P = 0.033). Our study showed a high prevalence of triple-therapy antithrombotic use in LVAD patients with no significant differences in bleeding, stroke or survival. However, the risk for pump thrombosis was lower at 1-year when compared to patient receiving MAPT.     

Low-dose oral vitamin K to normalize the international normalized ratio prior to surgery in patients who require temporary interruption of warfarin

Background In patients who require warfarin interruption before surgery and have an elevated international normalized ratio (INR) before surgery, low-dose vitamin K may normalize the INR in time for surgery. Patients and methods In a retrospective cohort study, we assessed the efficacy of 1 mg oral vitamin K to normalize the INR for surgery and whether resistance to re-anticoagulation occurs when warfarin is restarted after surgery. We studied a cohort of patients with an INR 1.4–1.9 on the day before surgery who received 1 mg oral vitamin K (vitamin K group), and a comparator group of patients with a normal INR (≤1.3) on the day before surgery who did not receive vitamin K (no vitamin K group). In both patient groups, we determined the proportion of patients with a normalized INR on the day of surgery and compared the mean INR after surgery when warfarin was resumed. Results Of 43 patients in the vitamin K group, the INR was normalized (≤1.3) in 33 patients (76.6; 95% confidence interval [CI]: 64.1–89.4), and the INR was normal or near-normal (≤1.4) in 39 patients (90.7; 95% CI: 82.0–99.4) on the day of surgery. The mean (standard deviation) INR in the vitamin K and no vitamin K group 4–8 days after surgery was 1.75 (0.34) and 1.59 (0.36), respectively (P = 0.56). Conclusions In patients requiring interruption of warfarin for surgery, 1 mg oral vitamin K on the day before surgery can normalize the INR by the day of surgery and may not confer resistance to warfarin re-anticoagulation after surgery.     

Warfarin dose reduction vs watchful waiting for mild elevations in the international normalized ratio

BACKGROUND: Whether clinicians should decrease the warfarin dose in response to a mild, asymptomatic elevation in the international normalized ratio (INR) is unknown. OBJECTIVES: The study objectives were as follows: (1) to evaluate the safety of an anticoagulation service (ACS) policy advocating that the warfarin dose not be changed for isolated, asymptomatic INRs of < or = 3.4; (2) to compare the dosing strategies of an ACS and primary care providers (PCPs); and (3) to quantify the relationship between reduction of the warfarin dose and the subsequent fall in the INR. DESIGN AND SETTING: Randomized controlled study of health maintenance organization outpatients who were receiving warfarin. PATIENTS: We identified 231 patients with a target INR of 2.5 and an isolated, asymptomatic INR between 3.2 and 3.4. Our ACS monitored 103 of the patients; PCPs monitored the remaining 128 patients. MEASUREMENTS: From all 231 patients, we obtained INRs and warfarin dosing history. From the 103 ACS enrollees, we also recorded adverse events. RESULTS: One ACS patient had epistaxis in the 30 days after the elevated INR. Twenty-three percent of ACS enrollees and 47% of PCP patients reduced their warfarin dose (p < 0.001). The median follow-up INRs were similar in both cohorts: 2.7 in the ACS enrollees and 2.6 in the PCP patients. However, in a subgroup analysis of 190 patients who presented with an INR of 3.2 or 3.3, ACS enrollees were more likely to have a follow-up INR in the range of 2 to 3 (p = 0.03). The median follow-up INR was 2.7 in 148 patients who maintained their warfarin dose, 2.5 in 77 patients who decreased their dose by 1 to 20%, and 1.7 in 6 patients who decreased their dose by 21 to 43% (p < 0.001). CONCLUSIONS: These findings support maintaining the same warfarin dose in asymptomatic patients with an INR of < or = 3.3, and reducing the dose for patients who have a greater INR or an increased risk of hemorrhage. Warfarin dose reductions > 20% should be avoided for mildly elevated INRs.     

Management and dosing of warfarin therapy

When initiating warfarin therapy, clinicians should avoid loading doses that can raise the International Normalized Ratio (INR) excessively; instead, warfarin should be initiated with a 5-mg dose (or 2 to 4 mg in the very elderly). With a 5-mg initial dose, the INR will not rise appreciably in the first 24 hours, except in rare patients who will ultimately require a very small daily dose (0.5 to 2.0 mg). Adjusting a steady-state warfarin dose depends on the measured INR values and clinical factors: the dose does not need to be adjusted for a single INR that is slightly out of range, and most changes should alter the total weekly dose by 5% to 20%. The INR should be monitored frequently (eg, 2 to 4 times per week) immediately after initiation of warfarin; subsequently, the interval between INR tests can be lengthened gradually (up to a maximum of 4 to 6 weeks) in patients with stable INR values. Patients who have an elevated INR will need more frequent testing and may also require vitamin K1. For example, a nonbleeding patient with an INR of 9 can be given low-dose vitamin K1 (eg, 2.5 mg phytonadione, by mouth). Patients who have an excessive INR with clinically important bleeding require clotting factors (eg, fresh-frozen plasma) as well as vitamin K1.     

Long-term continuous-flow left ventricular assist devices (LVAD) as bridge to heart transplantation

Heart transplantation (HTx) is the treatment of choice for end-stage heart failure but the limited availability of heart’s donors still represents a major issue. So long-term mechanical circulatory support (MCS) has been proposed as an alternative treatment option to assist patients scheduled on HTx waiting list bridging them for a variable time period to cardiac transplantation—the so-called bridge-to-transplantation (BTT) strategy. Nowadays approximately 90% of patients being considered for MCS receive a left ventricular assist device (LVAD). In fact, LVAD experienced several improvements in the last decade and the predominance of continuous-flow over pulsatile-flow technology has been evident since 2008. The aim of the present report is to give an overview of continuous-flow LVAD utilization in the specific setting of the BTT strategy taking into consideration the most representative articles of the scientific literature and focusing the attention on the evolution, clinical outcomes, relevant implications on the HTx strategy and future perspectives of the continuous-flow LVAD technology.     

Appraisal of current vitamin K dosing algorithms for the reversal of over-anticoagulation with warfarin: the need for a more tailored dosing regimen

Warfarin is the most commonly prescribed oral anticoagulant in the UK for the treatment and prevention of thromboembolic disorders. Vitamin K administration is an effective way of reversing excessive anticoagulation. Over-anticoagulated patients present with a wide range of international normalized ratio (INR) values and may respond differently to a fixed dose of vitamin K. Current dosing algorithms for vitamin K administration in the non-urgent treatment of over-anticoagulation do not take this variability in response into account. Consequently, over a third of over-anticoagulated patients still remain outside their target INR 24 h after treatment. Such patients are therefore prone to either haemorrhage (if the patient is still over-anticoagulated) or thromboembolism (if the INR reversal is over-corrected). A number of factors such as patient age, body weight, co-morbidity, frailty, warfarin daily dose and CYP2C9 and VKORC1 polymorphism could affect response to vitamin K and thus the rate and extent of INR reversal. There is a need for a more individualized approach to the reversal of over-anticoagulation in asymptomatic or mildly haemorrhagic patients in order to improve the safety of warfarin therapy.     

Evaluation of a warfarin initiation protocol for older people

Abstract
A protocol for initiation of warfarin therapy, targeted specifically for older people and based on individual responses to initial warfarin doses, was evaluated in a case-control study. People within the protocol group: (i) received higher initial doses of warfarin, (ii) reached an international normalized ratio (INR) of 2 more quickly, (iii) spent more time with INR of 2−3 in the first week and (iv) were less likely to be over-anticoagulated. However, the proportion of people who reached an INR of 2 too quickly (in <4 days) was no greater. The protocol correctly predicted the maintenance dose range of warfarin in over 70% of cases. (Intern Med J 2003; 33: 465−467)     

Improving Warfarin Management Within the Medical Home: A Health-System Approach

Background

Anticoagulation clinics have been considered the optimal strategy for warfarin management with demonstrated improved patient outcomes through increased time in therapeutic international normalized ratio (INR) range, decreased critical INR values, and decreased anticoagulation-related adverse events. However, not all health systems are able to support a specialized anticoagulation clinic or may see patient volume exceed available anticoagulation clinic resources. The purpose of this study was to utilize an anticoagulation clinic model to standardize warfarin management in a primary care clinic setting.

Paper-based dosing algorithms for maintenance of warfarin anticoagulation

We examined the quality of anticoagulation produced by two paper-based warfarin dosing algorithms in a randomized clinical trial of warfarin therapy. Fifty-eight patients were randomized to receive warfarin at a target international normalized ratio (INR) range of 2.1–3.0 and were followed for an average of 2.7 years. As a proportion of total patient-time, the percentage of time spent above, within, and below the therapeutic range was 11%, 71%, and 19% respectively. Fifty-six patients were randomized to receive warfarin at a higher target INR range (3.1–4.0) and had INRs within the therapeutic range for 40% of total patient time. We conclude that the performance, minimal cost, and ease-of-use of these algorithms make them well-suited for patient management within primary-care and research settings. Dr Crowther is a Career Investigator of Heart and Stroke Foundation of Canada This study was supported by the Canadian Institutes for Health Research.     

Warfarin and cranberry juice: an interaction?

Herein, the case is reported of a persistently elevated INR consequent to an interaction between warfarin and cranberry juice in a patient with a prosthetic mitral valve. The elevation in INR was noted two weeks after the patient began to drink cranberry juice. Subsequent symptoms included postoperative bleeding problems. The bleeding was thought due to a biologically plausible interaction between the drug and the juice. It was concluded that patients taking warfarin should limit their cranberry juice intake.