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Ujjin A, Wongcharoen W, Suwanagool A, Chai-Adisaksopha C. Optimal Strategies to Select Warfarin Dose for Thai Patients with Atrial Fibrillation. J Clin Med 2024; 13:2675. [PMID: 38731209 PMCID: PMC11084839 DOI: 10.3390/jcm13092675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 04/23/2024] [Accepted: 04/29/2024] [Indexed: 05/13/2024] Open
Abstract
Background: Warfarin has been the mainstay treatment for the prevention of stroke and systemic thromboembolism in patients with atrial fibrillation (AF). The optimal starting dose of warfarin remains unclear. Objective: To investigate the most optimal dosing strategies for warfarin starting dose in Thai patients with AF. Material and Methods: We enrolled consecutive AF patients who were starting on warfarin and resulting in a stable INR of 2.0-3.0 at two consecutive time points. We measured the dose of warfarin at which INR achieved the target range. The optimal dosage was defined as the difference from the actual dose within 20%. We compared strategies of warfarin dosing, including warfarin dosing formula, 2.5 mg, 3 mg and 5 mg doses. The primary endpoints were the proportions of patients in optimal, underdosing, and overdosing categories. Results: Among 1207 patients visiting the Outpatient Clinic between October 2011 and September 2021, 531 patients were identified with AF and INR in the therapeutic range of 2.0-3.0 on at least two consecutive visits. The mean age of participants was 68 ± 11 years, and men accounted for 44.4% of the population. The warfarin dosing formula resulted in optimal dosing in 37% and overdosing in 24% of cases, whereas the 2.5 mg, 3 mg and 5 mg doses resulted in optimal dosing in 36%, 39%, and 11%, and overdosing in 33%, 44% and 88% of patients, respectively (p < 0.01). Conclusions: In Thai patients with AF, the optimal warfarin starting dose may be 2.5 mg, 3 mg or a simplified warfarin dosing formula, whereas the 5 mg dose should be avoided due to the high risk of overdosing.
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Affiliation(s)
- Anunya Ujjin
- Division of Medicine, Neurological Institute of Thailand, Bangkok 10400, Thailand
| | - Wanwarang Wongcharoen
- Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 52000, Thailand
| | - Arisara Suwanagool
- Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Siriraj Hospital, Bangkok 10700, Thailand
| | - Chatree Chai-Adisaksopha
- Division of Hematology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 52000, Thailand
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Sridharan K, Banny RA, Husain A. Evaluation of Stable Doses of Warfarin in a Patient Cohort. Drug Res (Stuttg) 2020; 70:570-575. [PMID: 32820470 DOI: 10.1055/a-1228-5033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
BACKGROUND Definitions for stable dose of warfarin varies in the reported studies. International warfarin pharmacogenetic consortium (IWPC) algorithm was generated from the data based on these definitions. OBJECTIVE In the present study, we primarily evaluated whether any significant differences exist between the definitions for stable warfarin dose. METHODS A prospective cross-sectional study in adults receiving warfarin for at least 3 months was carried out. Stable doses of warfarin as defined in previous studies were compared with the standard definition. Bland-Altman plots, Pearson's correlation and intra-class coefficients (ICC) were used to assess the correlation, reliability and agreements between the doses. RESULTS Sixty-four patients were recruited. Twenty definitions were obtained from the previous studies. We observed that all but one showed very high or high positive correlations; and either excellent or good ICC. No significant differences between the doses initiated and predicted by IWPC algorithm. CONCLUSION We observed similar stable doses between the definitions except for one. Hence, IWPC algorithm may not have any bias associated with inclusion of any studies with variable definitions for stable warfarin dose.
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Affiliation(s)
- Kannan Sridharan
- Department of Pharmacology & Therapeutics, College of Medicine and Medical Sciences, Arabian Gulf University, Manama, Kingdom of Bahrain
| | - Rashed Al Banny
- Department of Cardiology, Salmaniya Medical Complex, Ministry of Health, Manama, Kingdom of Bahrain
| | - Aysha Husain
- Department of Cardiology, Salmaniya Medical Complex, Ministry of Health, Manama, Kingdom of Bahrain.,RCSI-Bahrain, Manama, Kingdom of Bahrain
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Shoji M, Suzuki S, Otsuka T, Arita T, Yagi N, Semba H, Kano H, Matsuno S, Kato Y, Uejima T, Oikawa Y, Matsuhama M, Yajima J, Yamashita T. A Simple Formula for Predicting the Maintenance Dose of Warfarin with Reference to the Initial Response to Low Dosing at an Outpatient Clinic. Intern Med 2020; 59:29-35. [PMID: 31511484 PMCID: PMC6995699 DOI: 10.2169/internalmedicine.3415-19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Objective The pharmacodynamic effect of warfarin varies among individuals, and its maintenance dose is widely distributed. Although many formulae for predicting the maintenance dose of warfarin have been developed, most of them are complex and not in practical use. Methods and Materials Among 12,738 new patients visiting the Cardiovascular Institute between 2004 and 2009, we identified 127 patients (66.6±8.8 years, 89 men) with atrial fibrillation for whom warfarin was newly started with an initial dose of 2 mg/day and the international normalized ratio (INR) at 1 year after warfarin was started was within the therapeutic range. The prediction models for the maintenance dose were developed by an exponential equation and a first-order equation. Results The initial response of the INR to the dose of 2 mg/day (initial INR) ranged from 1.00-3.24 (mean 1.43), while the maintenance dose of warfarin ranged from 0.5-14 mg (mean 3.8 mg). The maintenance dose showed an exponential correlation to the initial INR: (predicted maintenance dose) =5.522× (initial INR) -1.556 (R2=0.795, p<0.001). Excluding the patients with a poor response to the initial dose (initial INR <1.1, n=32) permitted a simple correlation with a first-order approximation: (predicted maintenance dose) =-2.009× (initial INR) +6.172 (R2=0.706, p<0.001). Conclusion We developed a simple formula for predicting the maintenance dose of warfarin using the initial response of the INR to low-dose warfarin.
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Affiliation(s)
- Masaaki Shoji
- Department of Cardiovascular Medicine, National Cancer Center Hospital, Japan
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Shinya Suzuki
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Takayuki Otsuka
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Takuto Arita
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Naoharu Yagi
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Hiroaki Semba
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Hiroto Kano
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Shunsuke Matsuno
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Yuko Kato
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Tokuhisa Uejima
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Yuji Oikawa
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Minoru Matsuhama
- Department of Cardiovascular Surgery, The Cardiovascular Institute, Japan
| | - Junji Yajima
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
| | - Takeshi Yamashita
- Department of Cardiovascular Medicine, The Cardiovascular Institute, Japan
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Saleh MI, Alzubiedi S. Dosage Individualization of Warfarin Using Artificial Neural Networks. Mol Diagn Ther 2014; 18:371-9. [DOI: 10.1007/s40291-014-0090-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Mueller JA, Patel T, Halawa A, Dumitrascu A, Dawson NL. Warfarin Dosing and Body Mass Index. Ann Pharmacother 2014; 48:584-8. [DOI: 10.1177/1060028013517541] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Background: Warfarin is still the most commonly used anticoagulant for the treatment of venous thromboembolism and other hypercoagulable states. Warfarin metabolism is affected by multiple factors, including diet, medications, and individual patient characteristics. As both underdosing and overdosing can increase risks to patients, several studies have attempted to develop dosing protocols. However, few have investigated how patient weight and body mass index (BMI) affect warfarin dosing. Objective: The objective of this study was to determine the association between BMI and the total weekly dose (TWD) of warfarin. Methods: In this retrospective study, we identified patients taking warfarin who had an international normalized ratio (INR) within the therapeutic range to assess if there was a significant correlation between TWD, that is, maintenance warfarin dosing, and BMI in obese and nonobese patients. Results: A total of 831 patients were studied, with a BMI range between 13.4 and 63.1 kg/m2. We found that BMI is positively correlated with the total weekly warfarin dose. Our study showed that for each 1-point increase in BMI, the weekly warfarin dose increased by 0.69 mg. We found that the average warfarin weekly dose in this population can be estimated using the formula: 12.34 + 0.69 × BMI. Conclusion: There is an association between BMI and the TWD of warfarin. This could have dosing implications for both patients and prescribers, as patients with a high BMI will be expected to require higher doses of warfarin to maintain a therapeutic INR.
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Fung E, Patsopoulos NA, Belknap SM, O'Rourke DJ, Robb JF, Anderson JL, Shworak NW, Moore JH. Effect of genetic variants, especially CYP2C9 and VKORC1, on the pharmacology of warfarin. Semin Thromb Hemost 2012; 38:893-904. [PMID: 23041981 DOI: 10.1055/s-0032-1328891] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The genes encoding the cytochrome P450 2C9 enzyme (CYP2C9) and vitamin K-epoxide reductase complex unit 1 (VKORC1) are major determinants of anticoagulant response to warfarin. Together with patient demographics and clinical information, they account for approximately one-half of the warfarin dose variance in individuals of European descent. Recent prospective and randomized controlled trial data support pharmacogenetic guidance with their use in warfarin dose initiation and titration. Benefits from pharmacogenetics-guided warfarin dosing have been reported to extend beyond the period of initial dosing, with supportive data indicating benefits to at least 3 months. The genetic effects of VKORC1 and CYP2C9 in African and Asian populations are concordant with those in individuals of European ancestry; however, frequency distribution of allelic variants can vary considerably between major populations. Future randomized controlled trials in multiethnic settings using population-specific dosing algorithms will allow us to further ascertain the generalizability and cost-effectiveness of pharmacogenetics-guided warfarin therapy. Additional genome-wide association studies may help us to improve and refine dosing algorithms and potentially identify novel biological pathways.
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Affiliation(s)
- Erik Fung
- Section of Cardiology, Heart & Vascular Center, Lebanon, New Hampshire 03756, USA.
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Abstract
INTRODUCTION This study aimed to investigate potential drug-drug interactions (pDDIs) with warfarin to minimize them, assess the acceptability of pharmaceutical interventions by the medical team and the impact on the international normalized ratio (INR) results. METHODS This pertains to a prospective study involving inpatients who started warfarin therapy in a university hospital located in southern Brazil. The pDDIs with warfarin were identified using the interaction screening program Drug-Reax, Micromedex Healthcare Series 1.0. RESULTS Two hundred and two inpatients were monitored. The mean of 10 different drugs was prescribed for each patient (SD = 3.6). At least 1 major or moderate pDDIs with warfarin per patient was observed, the mean was 3.6 (SD = 1.6). The most common pDDIs with warfarin involved in the increase of anticoagulation effect were enoxaparin (32.2%), simvastatin (27.6%), omeprazole (22.5%), and tramadol (21.5%). For 32 patients (15.8%), interventions were rejected, and they had a higher risk (relative risk= 2.17; 95% confidence interval 1.10-4.27) for abnormal test results (INR > 5). Multivariate analysis showed that age, length of hospital stay, exposure to ≥4 major or moderate pDDIs, and refusal of pharmacist recommendations contribute significantly to the patient's INR result >5. Consequently, the risk of bleeding is increased. CONCLUSIONS Major and moderate pDDIs with warfarin are very common in inpatients and are associated with INR results outside the therapeutic range. Pharmaceutical interventions concerning the management of interactions by providing information to physicians can improve the patient safety.
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Horne BD, Lenzini PA, Wadelius M, Jorgensen AL, Kimmel SE, Ridker PM, Eriksson N, Anderson JL, Pirmohamed M, Limdi NA, Pendleton RC, McMillin GA, Burmester JK, Kurnik D, Stein CM, Caldwell MD, Eby CS, Rane A, Lindh JD, Shin JG, Kim HS, Angchaisuksiri P, Glynn RJ, Kronquist KE, Carlquist JF, Grice GR, Barrack RL, Li J, Gage BF. Pharmacogenetic warfarin dose refinements remain significantly influenced by genetic factors after one week of therapy. Thromb Haemost 2012; 107:232-40. [PMID: 22186998 PMCID: PMC3292349 DOI: 10.1160/th11-06-0388] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 11/04/2011] [Indexed: 01/06/2023]
Abstract
By guiding initial warfarin dose, pharmacogenetic (PGx) algorithms may improve the safety of warfarin initiation. However, once international normalised ratio (INR) response is known, the contribution of PGx to dose refinements is uncertain. This study sought to develop and validate clinical and PGx dosing algorithms for warfarin dose refinement on days 6-11 after therapy initiation. An international sample of 2,022 patients at 13 medical centres on three continents provided clinical, INR, and genetic data at treatment days 6-11 to predict therapeutic warfarin dose. Independent derivation and retrospective validation samples were composed by randomly dividing the population (80%/20%). Prior warfarin doses were weighted by their expected effect on S-warfarin concentrations using an exponential-decay pharmacokinetic model. The INR divided by that "effective" dose constituted a treatment response index . Treatment response index, age, amiodarone, body surface area, warfarin indication, and target INR were associated with dose in the derivation sample. A clinical algorithm based on these factors was remarkably accurate: in the retrospective validation cohort its R(2) was 61.2% and median absolute error (MAE) was 5.0 mg/week. Accuracy and safety was confirmed in a prospective cohort (N=43). CYP2C9 variants and VKORC1-1639 G→A were significant dose predictors in both the derivation and validation samples. In the retrospective validation cohort, the PGx algorithm had: R(2)= 69.1% (p<0.05 vs. clinical algorithm), MAE= 4.7 mg/week. In conclusion, a pharmacogenetic warfarin dose-refinement algorithm based on clinical, INR, and genetic factors can explain at least 69.1% of therapeutic warfarin dose variability after about one week of therapy.
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Affiliation(s)
- Benjamin D Horne
- Cardiovascular Department, Intermountain Medical Center, Salt Lake City, Utah 84107, USA.
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9
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Gong IY, Schwarz UI, Crown N, Dresser GK, Lazo-Langner A, Zou G, Roden DM, Stein CM, Rodger M, Wells PS, Kim RB, Tirona RG. Clinical and genetic determinants of warfarin pharmacokinetics and pharmacodynamics during treatment initiation. PLoS One 2011; 6:e27808. [PMID: 22114699 PMCID: PMC3218053 DOI: 10.1371/journal.pone.0027808] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 10/25/2011] [Indexed: 11/24/2022] Open
Abstract
Variable warfarin response during treatment initiation poses a significant challenge to providing optimal anticoagulation therapy. We investigated the determinants of initial warfarin response in a cohort of 167 patients. During the first nine days of treatment with pharmacogenetics-guided dosing, S-warfarin plasma levels and international normalized ratio were obtained to serve as inputs to a pharmacokinetic-pharmacodynamic (PK-PD) model. Individual PK (S-warfarin clearance) and PD (Imax) parameter values were estimated. Regression analysis demonstrated that CYP2C9 genotype, kidney function, and gender were independent determinants of S-warfarin clearance. The values for Imax were dependent on VKORC1 and CYP4F2 genotypes, vitamin K status (as measured by plasma concentrations of proteins induced by vitamin K absence, PIVKA-II) and weight. Importantly, indication for warfarin was a major independent determinant of Imax during initiation, where PD sensitivity was greater in atrial fibrillation than venous thromboembolism. To demonstrate the utility of the global PK-PD model, we compared the predicted initial anticoagulation responses with previously established warfarin dosing algorithms. These insights and modeling approaches have application to personalized warfarin therapy.
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Affiliation(s)
- Inna Y. Gong
- Department of Physiology & Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Division of Clinical Pharmacology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Ute I. Schwarz
- Department of Physiology & Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Division of Clinical Pharmacology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Natalie Crown
- Division of Clinical Pharmacology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - George K. Dresser
- Division of Clinical Pharmacology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Alejandro Lazo-Langner
- Division of Hematology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Department of Epidemiology and Biostatistics, Robarts Clinical Trials, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - GuangYong Zou
- Department of Epidemiology and Biostatistics, Robarts Clinical Trials, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Dan M. Roden
- Division of Clinical Pharmacology, Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - C. Michael Stein
- Division of Clinical Pharmacology, Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Marc Rodger
- Department of Medicine, University of Ottawa, Ottawa Health Research Institute, Ottawa, Ontario, Canada
| | - Philip S. Wells
- Department of Medicine, University of Ottawa, Ottawa Health Research Institute, Ottawa, Ontario, Canada
| | - Richard B. Kim
- Department of Physiology & Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Division of Clinical Pharmacology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Rommel G. Tirona
- Department of Physiology & Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Division of Clinical Pharmacology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- * E-mail:
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Warfarin: Implementing Its Safe Use in Hospitalized Patients from Nursing Homes and Community Through a Performance Improvement Initiative. J Am Med Dir Assoc 2011; 12:518-23. [DOI: 10.1016/j.jamda.2010.04.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 04/19/2010] [Accepted: 04/19/2010] [Indexed: 11/20/2022]
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Keeling D, Baglin T, Tait C, Watson H, Perry D, Baglin C, Kitchen S, Makris M. Guidelines on oral anticoagulation with warfarin - fourth edition. Br J Haematol 2011; 154:311-24. [PMID: 21671894 DOI: 10.1111/j.1365-2141.2011.08753.x] [Citation(s) in RCA: 373] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Moreau C, Pautas E, Gouin-Thibault I, Golmard JL, Mahé I, Mulot C, Loriot MA, Siguret V. Predicting the warfarin maintenance dose in elderly inpatients at treatment initiation: accuracy of dosing algorithms incorporating or not VKORC1/CYP2C9 genotypes. J Thromb Haemost 2011; 9:711-8. [PMID: 21255252 DOI: 10.1111/j.1538-7836.2011.04213.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
BACKGROUND Initiating warfarin is challenging in frail elderly patients because of low-dose requirements and interindividual variability. OBJECTIVES We investigated whether incorporating VKORC1 and CYP2C9 genotype information in different models helped to predict the warfarin maintenance dose when added to clinical data and INR values at baseline (Day 0), and during warfarin induction. PATIENTS We prospectively enrolled 187 elderly inpatients (mean age, 85.6 years), all starting on warfarin using the same 'geriatric dosing-algorithm' based on the INR value measured on the day after three 4-mg warfarin doses (INR(3)) and on INR(6 ± 1). RESULTS On Day 0, the clinical model failed to accurately predict the maintenance dose (R(2) < 0.10). Adding the VKORC1 and CYP2C9 genotypes to the model increased R(2) to 0.31. On Day 3, the INR(3) value was the strongest predictor, completely embedding the VKORC1 genotype, whereas the CYP2C9 genotype remained a significant predictor (model- R(2) 0.55). On Day 6 ± 1, none of the genotypes predicted the maintenance dose. Finally, the simple 'geriatric dosing-algorithm' was the most accurate algorithm on Day 3 (R(2) 0.77) and Day 6 (R(2) 0.81), under-estimating (≥ 1 mg) and over-estimating the dose (≥ 1 mg) in fewer than 10% and 2% of patients, respectively. Clinical models and the 'geriatric dosing-algorithm' were validated on an independent sample. CONCLUSIONS Before starting warfarin therapy, the VKORC1 genotype is the best predictor of the maintenance dose. Once treatment is started using induction doses tailored for elderly patients, the contribution of VKORC1 and CYP2C9 genotypes in dose refinement is negligible compared with two INR values measured during the first week of treatment.
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Affiliation(s)
- C Moreau
- Université Paris Descartes, Paris, France
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Wittkowsky AK, Spinler SA, Dager W, Gulseth MP, Nutescu EA. Dosing guidelines, not protocols, for managing warfarin therapy. Am J Health Syst Pharm 2010; 67:1554-6. [PMID: 20811035 DOI: 10.2146/ajhp100064] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Affiliation(s)
- Ann K Wittkowsky
- School of Pharmacy, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA.
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Schulman S, Anderson DR, Bungard TJ, Jaeger T, Kahn SR, Wells P, Wilson SJ. Direct and indirect costs of management of long-term warfarin therapy in Canada. J Thromb Haemost 2010; 8:2192-200. [PMID: 20663051 DOI: 10.1111/j.1538-7836.2010.03989.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Comparisons of overall costs and resource utilization associated with anticoagulation management are important as new alternatives to warfarin are introduced. The aim of the present study was to assess total costs of warfarin-based anticoagulation in different health care models. METHODS Physician- or pharmacist-managed hospital- or community-based anticoagulation clinics in five Canadian provinces were asked to provide itemized information on costs for staff, laboratory, hardware and overheads associated with warfarin management. At each site, cohorts of patients were provided with diaries and participants prospectively entered all costs for warfarin medication and associated health professional contacts, travel to the laboratory, required assistance and time lost from work by patient or caregiver over 3months. All costs were calculated for a 3-month period. RESULTS Data from 429 patients at 15 sites were evaluated. The cost from the Ministry of Health perspective ranged from $108 to $199 per 3months in the different settings, the patient costs were $40-$80 and the total societal costs ranged from $188-$244. Sensitivity analyses with typical blood test intervals, the most prescribed strength of warfarin and dispensing fee from another province increased these estimates to $230-$302. When reimbursement for unemployed caregivers was also entered the total cost was $308-$503 per 3months. CONCLUSIONS The total cost for warfarin-based anticoagulation amounted to at least 10 times the lowest cost for the drug. The costs provided should be useful for comparisons with newer drugs without requirement for routine laboratory monitoring and dose adjustments.
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Affiliation(s)
- S Schulman
- Department of Medicine, McMaster University, Hamilton, ON, Canada.
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Kurnik D, Loebstein R, Halkin H, Gak E, Almog S. 10 years of oral anticoagulant pharmacogenomics: what difference will it make? A critical appraisal. Pharmacogenomics 2009; 10:1955-65. [DOI: 10.2217/pgs.09.149] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Since the first report on warfarin pharmacogenetics in 1999, genetic variants have emerged as an important predictor of warfarin maintenance doses before therapy is initiated, raising expectations of greatly improved clinical outcomes. However, much of the information on warfarin sensitivity conveyed by genetic variants is captured by early international normalized ratio values traditionally used to guide dose titration. Thus, inclusion of early international normalized ratios in prediction models reduces the contribution of genetics. Moreover, in large population cohorts, genetics explained only 20–30% of variance in warfarin doses. Finally, even pharmacogenetic prediction models did not predict doses reliably in the majority of at-risk patients with warfarin requirements at the low or high end of the dose range. Currently, the clinical utility and cost–effectiveness of pharmacogenetic-based dosing are being assessed in large prospective trials in various settings. In the interim, enthusiasm for warfarin pharmacogenetics should not supersede strict adherence to traditional measures used to optimize coumarin anticoagulation.
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Affiliation(s)
- Daniel Kurnik
- Division of Clinical Pharmacology and Toxicology, Sheba Medical Center, Tel Hashomer, Ramat Gan 52621, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ronen Loebstein
- Division of Clinical Pharmacology and Toxicology, Sheba Medical Center, Tel Hashomer, Ramat Gan 52621, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Hillel Halkin
- Division of Clinical Pharmacology and Toxicology, Sheba Medical Center, Tel Hashomer, Ramat Gan 52621, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Eva Gak
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Danek Gertner Institute of Human Genetics, Sheba Medical Center, Tel Hashomer, Israel
| | - Shlomo Almog
- Division of Clinical Pharmacology and Toxicology, Sheba Medical Center, Tel Hashomer, Ramat Gan 52621, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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