Angus Chun-tim Lo. / Thesis (M. Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 138-147). / ACKNOWLEDGEMENTS --- p.i / LIST OF PUBLICATIONS --- p.ii / ABSTRACT --- p.iii / ABBREVIATIONS --- p.viii / Chapter CHAPTER 1 --- General Introduction --- p.1 / Chapter CHAPTER 2 --- The Effects of Danshen (Salvia miltiorrhiza) on Pharmacokinetics and Pharmacodynamics of Warfarin / Chapter 2.1 --- Introduction --- p.35 / Chapter 2.2 --- Materials and Methods --- p.42 / Chapter 2.3 --- Results --- p.54 / Chapter 2.4 --- Discussion --- p.64 / Chapter CHAPTER 3 --- The Effects of Danshen (Salvia miltiorrhiza) on Pharmacological Properties of the Stereoisomers of Warfarin / Chapter 3.1 --- Introduction --- p.68 / Chapter 3.2 --- Materials and Methods --- p.72 / Chapter 3.3 --- Results --- p.84 / Chapter 3.4 --- Discussion --- p.99 / Chapter CHAPTER 4 --- The Effects of Danggui (Angelica sinensis) on Pharmacokinetics and Pharmacodynamics of Warfarin / Chapter 4.1 --- Introduction --- p.104 / Chapter 4.2 --- Materials and Methods --- p.114 / Chapter 4.3 --- Results --- p.120 / Chapter 4.4 --- Discussion --- p.127 / Chapter CHAPTER 5 --- General Conclusion --- p.131 / REFERENCES --- p.138

Postthrombotic syndrome (PTS) is a frequent complication of venous thromboembolism (VTE). Using MarketScan claims data from January 2012 to June 2015, we identified adults with a primary diagnosis code for VTE during a hospitalization/emergency department visit, ≥6 months of insurance coverage prior to the index event and newly started on rivaroxaban or warfarin within 30 days of the index VTE. Patients with <4-month follow-up postindex event or a claim for any anticoagulant during 6-month baseline period were excluded. Differences in baseline characteristics between rivaroxaban and warfarin users were adjusted for using inverse probability of treatment weights based on propensity scores. Patients were followed for the development of PTS starting 3 months after the index VTE. Cox regression was performed and reported as hazard ratios with 95% confidence intervals (CIs). In total, 10 463 rivaroxaban and 26 494 warfarin users were followed for a mean of 16 ± 9 (range, 4-39) months. Duration of anticoagulation was similar between cohorts (median = 6 months). Rivaroxaban was associated with a 23% (95% CI: 16-30) reduced hazard of PTS versus warfarin. Rivaroxaban was associated with a significant risk reduction in symptoms of PTS compared to warfarin in patients with VTE treated in routine practice.

Background Every year about 2,500 patients in Sweden undergo surgery for heart valve disease, primarily in the aortic valve.  In contrast to the mitral valve, which can be repaired in 70% of the cases, the aortic valve is normally replaced by a mechanical or biological prosthesis. A mechanical heart valve (MHV) necessitates lifelong anticoagulation treatment with a vitamin K antagonist, most commonly warfarin, due to the high thrombogenicity of the prosthesis. The quality of the warfarin treatment is crucial in these patients. Compared to other countries, treatment quality in Sweden is very high; nonetheless, there is always room for improvement. One of the ways to achieve this improvement is to implement computerized dosing assistance. Treatment recommendations for anticoagulation intensity are based on few and old studies, making these recommendations uncertain. There is therefore a need for studies designed to establish the appropriate level of anticoagulation therapy. Aim The aim of these studies was to investigate the efficacy and safety of anticoagulation treatment among patients with mechanical heart valve prostheses in Sweden; to assess whether computerized dosing can increase the treatment quality; to investigate the influence of the treatment quality, measured by Time in Therapeutic Range (TTR) and INR variability, on the risk of complications and, finally, to establish the optimal intensity of anticoagulation treatment in this group of patients. Methods Data were obtained from AuriculA – a national quality registry established in 2006, which currently includes approximately 50% of all patients treated with oral anticoagulation in Sweden. Study II used only data from AuriculA. 769,933 warfarin-dosing suggestions proposed by the dosing algorithm in AuriculA were analysed. Accepted dose suggestions (590,939) were compared with 178,994 manually-changed doses in regard to the resultant INR value, measured as mean error (deviation from target INR) and hit rate (number of INR samples within the target range 2-3). In study III, AuriculA was used to identify patients in Sundsvall and Malmö in the period 2008 – 2011 who were receiving warfarin for a mechanical heart valve prosthesis, as well as to retrieve their INR data. Data on background characteristics and bleedings or thromboembolic complications were manually retrieved from medical records by two investigators.  A total of 534 patients with mechanical heart valve prostheses were divided into quartiles based on TTR and were compared regarding the risk of complications. For Studies I and IV, data from AuriculA were merged with the Swedish National Patient Register, SWEDEHEART/ Heart surgery, and the Swedish Cause of Death Register, comprising in total 77,423 patients on warfarin with 217,804 treatment years. Every treatment period registered in AuriculA was given an individual identification number. During the study period a patient could have any number of treatment periods. The number of complications in total and in different patient groups within the study population was investigated. Complications were defined by ICD-10 codes. Major bleeding was defined as an event necessitating hospital treatment and given a discharge diagnosis with one of the ICD-10 codes reflecting bleeding, as listed in the Appendix. Bleeding events were divided into intracranial, gastrointestinal and other bleedings. Thromboembolic complications consist of venous events (deep vein thrombosis, pulmonary embolism, venous stroke) or arterial events (stroke, TIA, acute myocardial infarction, peripheral arterial embolism). Data were analysed using both simple, descriptive statistical methods and various tests such as Mann-Whitney (or two sample Wilcoxon), T-test, Chi 2 test, ANOVA, multivariate analysis with logistic regression and survival analysis with Cox Regression with proportional hazard assumption. Results Treatment quality  Mean TTR among all patients in Study I was 76.5% whereas patients with mechanical heart valve prostheses had a TTR of 74.5%. The annual incidence of major bleeding or thromboembolic events among all patients was 2.24% and 2.65%, respectively. The incidence of intracranial bleeding was 0.37% per year in the general population and 0.51% among patients with mechanical heart valve prostheses, who also had a higher bleeding rate in total (3.37% per year). Both the mean and median errors were smaller (0.44 vs. 0.48 and 0.3 vs. 0.4, respectively) and the hit rate was higher (0.72 vs. 0.67) when the dose suggested by the algorithm was accepted, compared to when it was manually changed. TTR  In Study III there was no significant difference in the risk of thromboembolism regardless of TTR level. Risk of bleeding in quartiles I and II was more than two times higher than in the quartile with TTR &gt;82.9. In Study IV, lower TTR (≤70%) was associated with a significantly higher rate of complications when compared with TTR &gt;70%. Bleeding risk was higher in the group with lower TTR (HR=2.43, CI 2.02-2.89, p&lt;0.001). After dividing patients into TTR quartiles, the rate of complications in total was significantly higher in quartiles I to III compared with quartile IV, which had the highest TTR. Risk of thromboembolism, major bleeding and death was higher in the first and second quartile compared to the quartile with the highest TTR. INR variability  Higher INR variability above mean (≥0.40) was related to a higher rate of complications compared with lower INR variability (&lt;0.40) as shown in Study IV. Bleeding risk was higher in the group with INR variability ≥0.40 (HR = 2.15, CI 1.75-2.61, p&lt;0.001). Comparison of quartile IV, which had the lowest INR variability, with the other three revealed that quartiles I and II, which had the highest INR variability, had significantly worse outcomes for all complications except for thromboembolic events, plus also death in quartile II. TTR and INR variability combined  High variability and low TTR combined was associated with a higher risk of bleedings (HR 2.50, CI 1.99-3.15), death (3.34, CI 2.62-4-27) and thrombosis (1.55, CI 1.21-1.99) compared to the best group. Level of anticoagulation Higher warfarin treatment intensity (mean INR 2.8-3.2 vs. 2.2-2.7) was associated with a higher rate of bleedings (HR 1.29, CI 1.06-1.58), death (1.73, CI 1.38-2.16) and complications in total (1.24, CI 1.06-1.41) after adjustment for MHV position, age and comorbidity. Conclusion Warfarin treatment quality is crucial for patients with mechanical heart valve prostheses. Computerized dosing assistance could help maintain high warfarin treatment quality. Well-managed treatment with TTR ≥70% and INR variability below mean &lt;0.40 is associated with a lower risk of serious complications compared with a lower TTR and higher INR variability. No benefit of higher warfarin treatment intensity was found for any valve type or position.

Contexte: Bien que plusieurs algorithmes pharmacogénétiques de prédiction de doses de warfarine aient été publiés, peu d’études ont comparé la validité de ces algorithmes en pratique clinique réelle. Objectif: Évaluer trois algorithmes pharmacogénomiques dans une population de patients qui initient un traitement à la warfarine et qui souffrent de fibrillation auriculaire ou de problèmes de valves cardiaques. Analyser la performance des algorithmes de Gage et al., de Michaud et al. ainsi que de l’IWPC quant à la prédiction de la dose de warfarine permettant d’atteindre l’INR thérapeutique. Méthodes: Un devis de cohorte rétrospectif fut utilisé afin d’évaluer la validité des algorithmes chez 605 patients ayant débuté une thérapie de warfarine à l’Institut de Cardiologie de Montréal. Le coefficient de corrélation de Pearson ainsi que l’erreur absolue moyenne ont été utilisés pour évaluer la précision des algorithmes. L’exactitude clinique des prédictions de doses fut évaluée en calculant le nombre de patients pour qui la dose prédite était sous-estimée, idéalement estimée ou surestimée. Enfin, la régression linéaire multiple a été utilisée pour évaluer la validité d’un modèle de prédiction de doses de warfarine obtenu en ajoutant de nouvelles covariables. Résultats : L’algorithme de Gage a obtenu la proportion de variation expliquée la plus élevée (R2 ajusté = 44 %) ainsi que la plus faible erreur absolue moyenne (MAE = 1.41 ± 0.06). De plus, la comparaison des proportions de patients ayant une dose prédite à moins de 20 % de la dose observée a confirmé que l’algorithme de Gage était également le plus performant. Conclusion : Le modèle publié par Gage en 2008 est l’algorithme pharmacogénétique le plus exact dans notre population pour prédire des doses thérapeutiques de warfarine. / Background: Although numerous genotype-based warfarin dosing algorithms have been published, there is little data comparing the predictive ability of these algorithms in real clinical practice. Objectives: Our goal was to evaluate the performance of pharmacogenetic algorithms in an unselected patient population initiating warfarin treatment for atrial fibrillation or valve disease in a real-world clinical setting. The principal objective of the analysis was to determine if Gage’s, Michaud’s, and IWPC algorithms could predict the dose achieving the therapeutic International normalized ratio (INR). Methods: Data from a retrospective cohort study of 605 patients initiating warfarin therapy at the Montreal Heart Institute was used. We compared the dose predicted by the algorithms to the dose achieving the therapeutic INR. Pearson’s correlation coefficient and mean absolute error (MAE) were used to evaluate the predictive accuracy of the algorithms. Clinical accuracy of the predictions was assessed by computing the proportion of patients in which the predicted dose was under-estimated, ideally estimated, or overestimated. Finally, we used multiple linear regression analysis to evaluate the accuracy of a predictive model obtained by adding additional covariables in predicting therapeutic warfarin doses. Results: The proportion of variation explained (adjusted R2) was the highest for Gage’s algorithm (R2 = 44 %) and the mean absolute error was the smallest for the predictions made by Gage’s algorithm (MAE = 1.41 ± 0.06). Moreover, when we compared the proportion of patients whose predicted doses are within ± 20 % of the observed stable dose, Gage’s algorithm also performed the best overall. Conclusion: The algorithm published by Gage et al. in 2008 is the most accurate pharmacogenetically based equation in predicting therapeutic warfarin dose in our study population.

The work presented in this dissertation focuses on two important medication-related problems in older adults, that is, untreated indication and drug-drug interactions, specifically with respect to a high-risk medication such as warfarin. Warfarin is a challenge to use in clinical practice due to its narrow therapeutic index, variability in dose-response and its interactions with numerous foods and drugs. This dissertation presents the research from two projects. In the first project the prevalence and predictors of warfarin use in nursing home (NH) residents with atrial fibrillation (AF), and use of secondary stroke prevention strategies was determined, in order to understand the patterns of anticoagulant use in frail NH residents and to identify patient characteristics associated with warfarin use. In the second project the effect of oral antibiotics on anticoagulation outcomes, when prescribed concomitantly with warfarin, was determined, in order to provide evidence on the clinical significance of warfarin-antibiotic interactions in older adults. In the first project a cross-sectional analysis of the prescription and resident files from the 2004 National Nursing Home Survey was done to determine the prevalence of AF and rates of use of warfarin and other anti-platelet agents, such as aspirin and clopidogrel. A multiple logistic regression model was used to determine factors associated with warfarin use. In this sample of older NH residents, 13% of residents had a diagnosis of AF, with indications for warfarin use and no contraindications to warfarin. From these patients, 30% received anticoagulant therapy with warfarin and 23% of the remaining patients received either aspirin or clopidogrel, suggesting that more than 50% of residents with AF did not receive any form of anticoagulant therapy. Non-white race, history of bleeding, and use of anti-platelet medications were associated with reduced odds of receiving warfarin. The second project was a retrospective medical record review of older patients from an outpatient anticoagulation clinic at a Veterans Affairs medical center. Results of the repeated measures ANOVA suggested a significant increase in post-antibiotic INR values with fluoroquinolones, azithromycin and amoxicillin. In addition, the percentage of patients with warfarin dose adjustments was significantly greater with fluoroquinolones and azithromycin as compared to cephalexin. No bleeding events were reported for any of these patients. In conclusion, the results of the projects suggest that there is underuse of warfarin in NH settings. Furthermore, antibiotics may be safely prescribed with warfarin in older adults as long as the INR is monitored closely.

OBJECTIVES: To assess cost effectiveness of anticoagulant clinics after FDA approval of New Oral Anticoagulants (NOACs) for preventing ischemic stroke in Atrial Fibrillation (AF) patients in the United States. METHODS: A decision tree was built to compare cost and effectiveness of 150mg dabigatran twice a day to adjusted dose of warfarin within anticoagulation clinic. The analysis was for one year using a societal perspective. The population in this analysis was a cohort of AF patients, ≥ 65 years old, with a CHADS2 score>2, and no contraindication to anticoagulation. RESULTS: The base case analysis showed that changing from warfarin with anticoagulant clinic to dabigatran without monitoring resulted in an additional $82,793 per QALY saved. Sensitivity analyses found that the model was sensitive to utilities of patients on warfarin. CONCLUSION: This study showed that substituting dabigatran for warfarin in this population was not within acceptable willingness to pay values for new therapy.

A raiva é uma zoonose nervosa, aguda e fatal que acomete todos os mamíferos e provoca enormes prejuízos para os pecuaristas. No ciclo epidemiológico rural, a doença é transmitida por morcegos hematófagos aos herbívoros e, ainda que haja um esforço por parte dos órgãos de defesa e dos produtores rurais para que se evite a ocorrência da doença, historicamente percebe-se que o combate à raiva com base somente na atuação em focos e vacinação de suscetíveis não elimina eficazmente o problema. Um dos pilares do Programa Nacional de Controle da Raiva dos Herbívoros (PNCRH) do Ministério da Agricultura, Pecuária e Abastecimento (MAPA) é o controle das populações de morcegos hematófagos pelo uso de pasta vampiricida. Porém, apesar dessa medida ser largamente utilizada como forma de controle da raiva rural, há poucas informações a respeito do real impacto que ela causa na ocorrência de focos de raiva no Espírito Santo. Através da análise de dados coletados pelo Instituto de Defesa Animal e Florestal do Espírito Santo (IDAF), pelo Instituto Brasileiro de Geografia e Estatística (IBGE) e pelo Instituto Jones dos Santos Neves (IJSN) determinou-se o efeito do uso da pasta vampiricida em morcegos hematófagos na ocorrência de focos de raiva no Espírito Santo em 2011, 2012 e 2013. Para tal, foram utilizadas as coordenadas de focos de raiva e do uso de pasta vampiricida pelas equipes de captura de morcegos. As coordenadas georreferenciadas foram representadas em um Sistema de Informação Geográfica e analisadas utilizando-se o modelo de interpolação pelo método do &ldquo;inverso das distâncias&rdquo; A prevenção da ocorrência de focos de raiva ocorreu quando o impacto do tratamento foi alto e muito alto, porém a área de impacto é espacialmente limitada. Já nas áreas onde o impacto foi baixo ou muito baixo, a doença continuou grassando. Aspectos da biologia e ecologia dos morcegos hematófagos, como o comportamento das colônias após o uso da pasta e a possível dispersão do vírus, precisam ser melhor estudados. / Rabies is a nervous, acute and fatal zoonosis that affects mammals and causes enormous economic losses to farmers. In its rural epidemiological cycle, the disease is transmitted by common vampire bats to herbivores. There is a constant effort from cattle breeders and public veterinary services to avoid rabies occurrence. However, it has been reported that only livestock vaccination and outbreak control actions do not effectively control the problem. One of the pillars of the Herbivore Rabies National Control Program (PNCRH) from the the Ministry of Agriculture, Livestock and Supply of Brazil (MAPA) is the control of vampire bat populations through vampiricid gel use. However, even though this measure is largely used as a way to control cattle rabies, there is a lack of information regarding its actual impact in the occurrence of rabies outbreaks in the state of Espírito Santo. Through analysis of data collected by the Forestry and Animal Surveillance Institute of Espírito Santo (IDAF), the Brazilian Statistics and Geography Institute (IBGE) and the Jones dos Santos Neves Institute, we were able to establish the effect of vampiricid gel use on rabies outbreaks in Espírito Santo in 2011, 2012 and 2013. In order to do so, we used the geographic coordinates of rabies occurrence and vampiricid gel use. These references were then represented on a Geographic Information System and analyzed with an in verse distance weighted (IDW) interpolation method. Outbreaks were prevented when impact was high or very high; however, the impact areas in these cases appeared to be spatially limited. In areas where impact was considered low or very low, rabies prevailed. Vampire bat ecology and biology aspects, such as colony behavior after vampiricid gel use and possible virus dispersion, should be investigated further.

This thesis combines five published research papers investigating methods of improving the safety and control of oral anticoagulation, with the use of computer assisted dosage and the standardisation of the International Normalised Ratio (INR). The INR is a conventional measurement derived from the time it takes blood of a patient to form a clot and is used to monitor the effects of widely used oral anticoagulants such as warfarin for the prevention of stroke and other related disorders. The first paper investigates whether the use of computer-assisted programs was as safe and effective as medical staff manual dosage in the prevention of bleeding or thrombotic complications during oral anticoagulant treatment. This was an international multi-centre randomised study conducted by the European Action on Anticoagulation (EAA) investigating the clinical benefit of two computer programs, PARMA 5 (Italy) and DAWN AC (UK). Composite clinical events were reduced by 7.6% using computer programs, though not achieving statistical significance (p=0.1), showing computer programs to be not dissimilar to medical staff dosage. The second paper recommends guidelines for screening safety and effectiveness of other marketed computer programs based on the results of the EAA study. A process for a candidate computer program to achieve non-inferiority relative to the medical staff dosage arm from the EAA study is explained. The third paper introduces a modified approach to the 'Direct INR' method for the standardisation of INR termed the 'Prothrombin Time/INR Line' (PT/INR). This was directly compared to the local International Sensitivity Index (ISI) calibration procedure originally approved by the World Health Organisation and later by the United States Food and Drug Administration (FDA). Using manually certified lyophilised plasmas tested by specialist centres, the PT/INR Line using a set of 5 calibrant plasmas to establish a fitted line to estimate local INR was shown to be as effective as the FDA procedure. The fourth paper investigates the PT/INR Line further by using simulated sets of calibrant plasmas across the therapeutic range of 2.0-4.5 INR and determining the PT/INR Line. Local INR of five validation plasmas, certified by 3 centres using the manual PT technique, was determined using the estimated PT/INR Lines and compared with local ISI calibration. Using 4 or 5 calibrant plasmas to determine the PT/INR Line was shown to be as accurate as local ISI calibrations for reliable local INR.The fifth and final paper assessed INR variability and control in oral anticoagulant therapy using a method termed the Variance Growth Rate (VGR), and compared its predictive ability of adverse events with the Time in Target INR range (TIR), the conventional method used in evaluating the quality of oral anticoagulant therapy. The VGR method was shown to be a better predictor of adverse bleeding or thrombotic episodes in the short term period prior to an event (3 and 6 months) compared with TIR.

A raiva é uma zoonose nervosa, aguda e fatal que acomete todos os mamíferos e provoca enormes prejuízos para os pecuaristas. No ciclo epidemiológico rural, a doença é transmitida por morcegos hematófagos aos herbívoros e, ainda que haja um esforço por parte dos órgãos de defesa e dos produtores rurais para que se evite a ocorrência da doença, historicamente percebe-se que o combate à raiva com base somente na atuação em focos e vacinação de suscetíveis não elimina eficazmente o problema. Um dos pilares do Programa Nacional de Controle da Raiva dos Herbívoros (PNCRH) do Ministério da Agricultura, Pecuária e Abastecimento (MAPA) é o controle das populações de morcegos hematófagos pelo uso de pasta vampiricida. Porém, apesar dessa medida ser largamente utilizada como forma de controle da raiva rural, há poucas informações a respeito do real impacto que ela causa na ocorrência de focos de raiva no Espírito Santo. Através da análise de dados coletados pelo Instituto de Defesa Animal e Florestal do Espírito Santo (IDAF), pelo Instituto Brasileiro de Geografia e Estatística (IBGE) e pelo Instituto Jones dos Santos Neves (IJSN) determinou-se o efeito do uso da pasta vampiricida em morcegos hematófagos na ocorrência de focos de raiva no Espírito Santo em 2011, 2012 e 2013. Para tal, foram utilizadas as coordenadas de focos de raiva e do uso de pasta vampiricida pelas equipes de captura de morcegos. As coordenadas georreferenciadas foram representadas em um Sistema de Informação Geográfica e analisadas utilizando-se o modelo de interpolação pelo método do &ldquo;inverso das distâncias&rdquo; A prevenção da ocorrência de focos de raiva ocorreu quando o impacto do tratamento foi alto e muito alto, porém a área de impacto é espacialmente limitada. Já nas áreas onde o impacto foi baixo ou muito baixo, a doença continuou grassando. Aspectos da biologia e ecologia dos morcegos hematófagos, como o comportamento das colônias após o uso da pasta e a possível dispersão do vírus, precisam ser melhor estudados. / Rabies is a nervous, acute and fatal zoonosis that affects mammals and causes enormous economic losses to farmers. In its rural epidemiological cycle, the disease is transmitted by common vampire bats to herbivores. There is a constant effort from cattle breeders and public veterinary services to avoid rabies occurrence. However, it has been reported that only livestock vaccination and outbreak control actions do not effectively control the problem. One of the pillars of the Herbivore Rabies National Control Program (PNCRH) from the the Ministry of Agriculture, Livestock and Supply of Brazil (MAPA) is the control of vampire bat populations through vampiricid gel use. However, even though this measure is largely used as a way to control cattle rabies, there is a lack of information regarding its actual impact in the occurrence of rabies outbreaks in the state of Espírito Santo. Through analysis of data collected by the Forestry and Animal Surveillance Institute of Espírito Santo (IDAF), the Brazilian Statistics and Geography Institute (IBGE) and the Jones dos Santos Neves Institute, we were able to establish the effect of vampiricid gel use on rabies outbreaks in Espírito Santo in 2011, 2012 and 2013. In order to do so, we used the geographic coordinates of rabies occurrence and vampiricid gel use. These references were then represented on a Geographic Information System and analyzed with an in verse distance weighted (IDW) interpolation method. Outbreaks were prevented when impact was high or very high; however, the impact areas in these cases appeared to be spatially limited. In areas where impact was considered low or very low, rabies prevailed. Vampire bat ecology and biology aspects, such as colony behavior after vampiricid gel use and possible virus dispersion, should be investigated further.

Atrial fibrillation (AF) is a common cardiac arrhythmia that requires extensive medical and pharmaceutical management. The coagulation antagonist warfarin is commonly prescribed to reduce AF-associated stroke. Although warfarin effectively mediates thromboembolitic risk, its management is complex as many factors influence its therapeutic range including: genetics, diet, medication, and herbal and dietary supplement (HDS) interactions. Lack of patient knowledge regarding these factors contributes to poor patient outcomes. With the emerging epidemic of AF, readily available educational tools are necessary to improve patient outcomes while reducing clinician burden. The purpose of this study was to develop both a self-learning, DVD-based and one-on-one education program to educate patients with atrial fibrillation about the risks of HDS-warfarin interactions and to compare education method efficacy in AF disease management. This study found patients lack knowledge regarding HDS-warfarin management, and both DVD-based and one-on-one education models could increase patient knowledge regarding HDS-warfarin factors. It is hypothesized this education method may be employed to further educate chronic disease populations about essential disease-associated factors to improve outcomes while reducing clinical burdens.