Waran används sedan 60 år som blodförtunnande läkemedel för att förebygga eller förhindra progress av blodproppssjukdom. I Sverige behandlas årligen cirka 1 % av befolkningen med waran. I Östergötland uppskattas antal waranpatienter till cirka 3000. Waran hämmar enzymet VKORC1 som ansvarar för vitamin K omsättningen i kroppen. Vitamin K behövs som kofaktor för flera koagulationsfaktorer. Behandling med waran är förenad med en svår balansgång och kräver en noggrann dosering. Stora skillnader i dosbehov mellan olika individer, beroende på ärftliga och miljöfaktorer, gör waran till ett svårhanterligt läkemedel. För låg dos medför otillräcklig effekt och därmed risk för minskat skydd mot blodproppssjukdom. För hög dos leder till allvarliga blödningskomplikationer. Uppskattningsvis 1 – 3 % livshotande blödningsfall registreras årligen efter waranbehandling. Därför måste behandlingen kontrolleras noga med analys av protrombinkomplex (PK) och dosjusteringar göras med ledning av resultaten. Två olika metoder finns att använda för mätning av PK. I Norden och i Japan används Owrens metod (utvecklat i Norge under 40- och 50-talet av Paul Owren). I de flesta andra länder används Quickmetoden (utvecklat i USA under 30-talet av Armand Quick). Den senare metoden är förenad med stora variationer mellan olika analyslaboratorier. I Norden, däremot, där Owrens metod används finns det ofta bra överensstämmelse mellan olika laboratorier i PK-resultat. Beroende på vilken PK-metod som används, kan samma patient få olika warandoser vilket ökar risker för under- eller överbehandling. Vi har i samarbete med flera sjukhus och antikoagulationsmottagningar (AK-mottagningar) i sydöstra Sverige studerat dels mekanismerna bakom skillnader i warandos mellan olika patienter, och dels tittat varför de olika PK-metoder skiljer sig så mycket som de gör. I studien har vi identifierat genetiska varianter av enzymet VKORC1. Av de undersökta patienter som gick på waran under längre tid, har vi identifierat en grupp som markant skiljde sig från de övriga. Denna grupp hade warandoser som var betydligt lägre än de övriga. När vi kartlade deras arvsmassa, fann vi att lågdospatienterna hade genvarianten VKORC1*2. Dessutom hade patienter med denna variant svårigheter att få stabila PK-värden. De gjorde också fler besök på AK-mottagningar än andra patienter. Vi har därför konstaterat att en del av de problem som är förenade med waranbehnadlingen kan förklaras av VKORC1*2 varianten. Vetskap om denna variant skulle troligen underlätta behandlingen framför allt under inledningsfasen då patienter med VKORC1*2 riskerar blödningar på grund av överdosering. Vi har identifierat att provförspädning enligt Owrens metod är nödvändig för harmonisering av PK-resultatet mellan olika länder. Quickmetoden använder inte förspädning av patientprov till skillnad från Owrens metod. När vi modifierade en Quickmetod genom att förspäda prover enligt Owrens metod noterade vi en bra överensstämmelse mellan de två olika metoderna. Däremot var resultatet sämre utan provförspädning. Vi anser att Quickmetoder kan uppnå lika bra resultat som Owrens metod om prover förspäds som i Owrens metod. Det skulle gynna patienter som reser mellan olika regioner eller länder och leda till en bättre övervakning av waranbehandling internationellt. I studien har dessutom en metod för mätning av waran i blodet utvecklats. Metoden som är den enda i sitt slag i Norden ger möjlighet att studera hur läkemedlet beter sig i kroppen. Vi har med denna metod kunnat upptäcka patienter som har onormala nedbrytningar av waran. / Warfarin was introduced more than 60 years ago and is used worldwide for the prophylaxis of arterial and venous thromboembolism in primary and secondary prevention. The drug is orally administered as a racemic mixture of (R)- and (S)-enantiomers. The (S)-form is mainly responsible for the anticoagulant effect and is metabolised by CYP2C9 enzyme in the liver microsomes. Warfarin exerts its pharmacological action by inhibiting the key enzyme (VKORC1) that regenerates vitamin K from an oxidised state to a reduced form. The latter is a cofactor for the post-translational modification of a number of proteins including coagulation factors II, VII, IX and X. The vitamin K-dependent modification provides these factors with the calcium-binding ability they require for the interaction with cell membranes of their target cells such as platelets. Warfarin is monitored by measuring prothrombin time (PT) expressed as INR. Two main methods exist for PT analysis. The Owren method is used mainly in the Nordic and Baltic countries, in Japan, whereas the Quick method is employed in most other countries. Warfarin management is associated with some complications. Unlike many other drugs the dose for a given patient cannot be estimated beforehand, dose-response relationship is not predictable, and the prevention of thrombosis must be balanced against the risk of bleeding. Furthermore, the different PT methods used to monitor the drug are sometimes not in agreement and show significant discrepancies in results. In an attempt to clarify the mechanisms influencing the inter-individual variations in warfarin therapy and to detect the factors that contribute to differences between PT methods, studies were conducted in collaboration with hospitals and anticoagulation clinics in the south-eastern region of Sweden. First, a stereo-specific HPLC method for measurement of warfarin enantiomers was developed and validated. With this method, the levels of plasma warfarin following its oral administration can be studied and evaluated. Abnormal clearance in some patients can be detected, and patient compliance can be verified. Furthermore, differing ratios of (S)- and (R)-isomers can be identified. The impact of common VKORC1 polymorphisms on warfarin therapy was investigated. This study has shown that the VKORC1*2 haplotype is an important genetic determinant for warfarin dosage and is associated with difficulties in attaining and retaining therapeutic PT-INR. Further, significant differences in warfarin S/R-ratio was detected between patients with VKORC1*2 and VKORC1*3 or VKORC1*4 variants. This difference was not coupled with CYP2C9 genotype. The effects of predilution of patient plasma samples, sources of thromboplastin and deficient plasma on between PT methods agreement were studied. This study has revealed that sample predilution according to the Owren method is to be preferred for the harmonisation of PT results. Undiluted samples, in contrast, according to the Quick method have shown reduced correlation between two different thromboplastin reagents. Sources of thromboplastin and deficient plasma were only of minor importance.

Vitamin K Antagonists [VKA] are the most frequently used oral anticoagulants in clinical practice; however, many patients fail to achieve adequate anticoagulation control. We conducted a randomized, placebo controlled, double blind study of Vitamin K1 (200mcg per day, Swanson Vitamins) in a population with predominantly venous thromboembolism aimed at evaluating its effectiveness in improving anticoagulation control in unstable patients. This study also aimed to evaluate the impact that clinical variables, patient anticoagulation knowledge, and genetic polymorphisms in genes known to impact warfarin and Vitamin K metabolism [VKORC1, CYP4F2, CYP2C9] had on anticoagulation control and intervention effectiveness. A total of N=54 patients were enrolled in the study over 15 months [January 2009 to June 2010]. Change score analysis and multivariate linear regression modelling of anticoagulation control measures were performed. No statistically significant reduction was observed in the Vitamin K1 arm for percent time in therapeutic range; however, reduction was observed in standard deviation of INRs [Change Score Vitamin K = -0.259, p=0.0261; Regression Model 95% C.I Beta Vitamin K = 0.38 to -0.08] during the intervention period. Adjusting for treatment group allocation, independent predictors of increased INR standard deviation included: >5 alcoholic drinks per week [95% C.I Beta = 0.04 to 0.41], self-reported dosing errors [95% C.I Beta = 0.13 to 0.47], and missed INR appointments [95% C.I Beta = 0.002 to 0.05]

Warfarin is one of the most widely used anticoagulants. Therapy is complicated by warfarin’s narrow therapeutic range and pronounced variability in individual dose requirements. Although warfarin therapy is uncommon in children, it is crucial for children with certain congenital or acquired heart diseases. Treatment in children is especially difficult due to the lack of i) a decision support tool for efficient and consistent dose adjustments, and ii) a flexible warfarin formulation for accurate and reproducible dosing. The overall aim of this thesis was to develop a PKPD-based pharmacometric model for warfarin that describes the dose-response relationship over time, and to identify important predictors that influence individual dose requirements both in adults and children. Special emphasis was placed on investigating the contribution of genetic factors to the observed variability. A clinically useful pharmacometric model for warfarin has been developed using NONMEM. The model has been successfully reformulated into a KPD-model that describes the relationship between warfarin dose and INR response, and that is applicable to both adults and children. From a clinical perspective, this is a very important change since it allows the use of information on dose and INR that is available routinely. The model incorporates both patient and clinical characteristics, such as age, weight, CYP2C9 and VKORC1 genotype, and baseline and target INR, for the prediction of an individualised starting dose. It also enables the use of information from previous doses and INR observations to further individualise the dose a posteriori using a Bayesian forecasting method. The NONMEM model has been transferred to a user-friendly, platform independent tool to aid use in clinical practice. The tool can be used for a priori and a posteriori individualisation of warfarin therapy in both adults and children. The tool should ensure consistent dose adjustment practices, and provide more efficient individualisation of warfarin dosing in all patients, irrespective of age, body weight, CYP2C9 or VKORC1 genotype, baseline or target INR. The expected outcome is improved warfarin therapy compared with empirical dosing, with patients achieving a therapeutic and stable INR faster and avoiding high INRs that increase the risk of bleeding.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 75-83).

published_or_final_version / Medicine / Master / Master of Research in Medicine

Herbal medicines are widely used in our community. A survey of Australian consumers indicated that 60% had used complementary and/or alternative medicines in the past year with the majority not informing their doctor that they were using herbal medicines. Little is known about the potentially serious consequences of interactions between herbal and conventional medicines. Warfarin has an important role in treating people with heart disease, yet it has a narrow therapeutic range, is highly bound to plasma proteins, and is metabolised by cytochrome P450. This creates the potential for life-threatening interactions with other drugs and foods leading to excessive bleeding. Hence, warfarin is one of the most frequently investigated drugs for interaction studies. Early clinical reports suggest that there exists the potential for an interaction between warfarin and four herbal medicines: St John�s wort, ginseng, ginkgo and ginger. However, these herb-drug combinations have never been conclusively studied. The two clinical studies conducted as part of this research had an identical study design. Twenty-four healthy male subjects were recruited into the two separate studies. This was an open label, three-way crossover randomised study in twelve healthy male subjects, who received a single 25 mg dose of warfarin alone or after 14 days pre-treatment with St John�s wort, or 7 days pre-treatment with ginseng. Dosing with St John�s wort or ginseng was continued for 7 days after administration of the warfarin dose in study I or who received a single 25 mg dose of warfarin alone or after 7 days pre-treatment with recommended doses of ginkgo or ginger from single ingredient products of known quality. Dosing with ginkgo or ginger was continued for 7 days after administration of the warfarin dose in study II. Platelet aggregation, international normalised ratio (INR) of prothrombin time, warfarin enantiomer protein binding, warfarin enantiomer concentrations in plasma and S-7-hydroxywarfarin concentration in urine were measured in both studies. Statistical comparisons were made using ANOVA and 95% confidence interval (CI) for mean value and 90% CI for geometric mean ratio value are reported. n study I, the mean (95% CI) apparent clearance of S-warfarin after warfarin alone or with St John�s wort or ginseng were, respectively, 198 (174 � 223) ml/h, 269 (241 � 297) ml/h and 220 (201 � 238) ml/h. The respective apparent clearances of R-warfarin were 110 (94 � 126) ml/h, 142 (123 � 161) ml/h and 119 (106 � 131) ml/h. The mean ratio of apparent clearance for S-warfarin was 1.29 (1.16-1.46) and for R-warfarin was 1.23 (1.11-1.37) when St John�s wort was co-administered. The mean ratio of AUC0-168 of INR was 0.79 (0.70 - 0.95) when St John�s wort was co-administered. The urinary excretion ratio of S-7-hydroxywarfarin after administration of warfarin alone was 0.04 (0.03 � 0.06) mg/h and there was no significant difference following treatment with either St John�s wort 0.03 (0.02 � 0.04) mg/h or ginseng 0.03 (0.02 � 0.04) mg/h. The ratio of geometric means for S-7-hydroxywarfarin UER was 0.82 (0.61-1.12) for St John�s wort, and 0.68 (0.50-0.91) for ginseng. St John�s wort and ginseng did not affect the apparent volumes of distribution or protein binding of warfarin enantiomers. In study II, the mean (95% CI) apparent clearance of S-warfarin after warfarin alone, with ginkgo or ginger were 189 (167 � 210) ml/h, 200 (173 � 227) ml/h and 201 (171 � 231) ml/h, respectively. The respective apparent clearances of R-warfarin were 127 (106 � 149) ml/h, 126 (111 � 141) ml/h and 131 (106 � 156) ml/h. The mean ratio of apparent clearance for S-warfarin was 1.05 (0.98 -1.12) and for R-warfarin was 1.00 (0.93 -1.08) when co-administered with ginkgo. The mean ratio of AUC0-168 of INR was 0.93 (0.81 -1.05) when co-administered with ginkgo. The mean ratio of apparent clearance for S-warfarin was 1.05 (0.97 -1.13) and for R-warfarin was 1.02 (0.95 -1.10) when co-administered with ginger. The mean ratio of AUC0-168 of INR was 1.01 (0.93 -1.15) when co-administered with ginger. The urinary excretion ratio (UER) of S-7-hydroxywarfarin after administration of warfarin alone was 0.04 (0.03 � 0.05) mg/h and there was no significant difference following treatment with either ginkgo 0.04 (0.03 � 0.04) mg/h or ginger 0.03 (0.02 � 0.04) mg/h. The ratio of geometric means for S-7-hydroxywarfarin UER was 1.07 (0.69-1.67) for ginkgo, and 1.00 (0.64-1.56) for ginger. Ginkgo and ginger did not affect the apparent volumes of distribution or protein binding of either S-warfarin or R-warfarin. In conclusion, St John�s wort significantly induced the apparent clearance of both S-warfarin and R-warfarin, which in turn resulted in a significant reduction in the pharmacological effect of rac-warfarin. Ginseng, ginkgo and ginger at recommended doses affect neither clotting status, nor the pharmacokinetics or pharmacodynamics of either S-warfarin or R-warfarin in healthy subjects.

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. This thesis is subject to a two year embargo until 17/11/2007 and may only be viewed and copied with the permission of the author. For further information please Contact the Archivist. Includes bibliographical references: leaf 226-249.

Thesis (Ph.D.). / Written for the Dept. of Epidemiology, Biostatistics and Occupational Health. Title from title page of PDF (viewed 2008/07/23). Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (leaves 91-124).

Introdução: A varfarina é um dos anticoagulantes orais (ACO) mais utilizados na atenção primária a saúde. Com janela terapêutica estreita, exibe grande variabilidade de resposta farmacológica, e maior suscetibilidade de eventos adversos, como sangramentos e tromboembolismo venoso. Entre os fatores que influenciam na variabilidade de dose destaca-se as interações tanto com medicamentos, como com a dieta e o polimorfismo genético. Objetivos: Estimar a incidência de eventos adversos relacionados ao uso de varfarina e descrever o itinerário do usuário pelo sistema público de saúde para resolução dos problemas. Métodos: trata-se de uma coorte prospectiva realizada por um período de 18 meses com usuários do serviço público de saúde, em uso de varfarina, do município de Ijuí/RS. Os dados foram coletados por entrevistas mensais nas residências e complementados com informações médicas obtidas na atenção primária e terciária. As interações medicamentosas foram checadas em bases de dados e os hábitos alimentares conforme metodologia validada. A estatística utilizada para associar sangramento e Time in Therapeutic Range (TTR) e os fatores de risco foi teste de Poison. O projeto foi aprovado no Comitê de Ética em Pesquisa da UFRGS, com parecer número 336.259/2013. Resultados: Foram entrevistados e acompanhados 69 pacientes, sendo que 64 concluíram o acompanhamento e 5 faleceram durante o estudo, 55,1% eram do sexo feminino, com idade média de 64,3 ±13,7 anos. O tempo médio de uso de varfarina foi de 5,5 anos, a dose média semanal foi de 30,69±15,19mg e o principal motivo para uso de varfarina foi prótese valvular (39,7%). A média de medicamentos utilizados por usuário foi de 9,6±4,5. Quanto aos eventos, os sangramentos tiveram incidência de 37,7/100 pacientes/ano, o tromboembolismo de 4,8/100 pacientes/ano e de óbitos de 4,8/100 pacientes/ano. Os sangramentos apresentaram associação com possuir mais que três interações medicamentosas com a varfarina (p=0,048) e com uso de medicamentos por automedicação (p=0,030). Já para o TTR houve associação com a idade inferior a 65 anos (p=0,032). E 67 usuários estavam suscetíveis a interações medicamentosasas com varfarina, com predomínio das moderadas, sendo a média de interações com este medicamento de 2,91±1,52. A maioria das interações agiam sobre o efeito anticoagulante da varfarina, aumentando a probabilidade de sangramento. Entre as interações que os usuários apresentavam, no momento do sangramento, as mais frequentes foram com: omeprazol, sinvastatina e paracetamol. A maioria dos entrevistados apresentou consumo baixo de vitamina K. Verificou-se que sangramentos e tromboembolismos venosos foram mais frequentes nos pacientes em início de tratamento. E todos os pacientes que foram a óbito durante o acompanhamento (5) eram pacientes com mais de um ano de uso de varfarina. Para a resolução de eventos adversos na maioria dos casos o paciente realizou cuidado domiciliar (53,4%), seguido por busca pela Unidades Básicas de Saúde, 7 pacientes buscaram o serviço de emergência e 5 realizaram internação hospitalar. Observou-se que aproximadamente metade dos pacientes não mostrou seus exames de INR (Razão Normalizada Internacional) ao médico. E na falta de varfarina na rede pública de saúde do município, que ocorreu entre os meses 13 e 16, entre 24,9 a 43,5%, deixaram de usar o medicamento. Os resultados do polimorfismo demonstram que 47 (71,2%) não apresentam polimorfismo ao genótipo CYP2C9, e 24 (36,4%) ao genótipo VKORC1. Avaliando os dois genótipos associados, verifica-se que 17 (25,8%) não apresentam polimorfismo a nenhum destes. Não foi observada associação estatística do polimorfismo com sexo e raça. Observou-se diferença significativa entre a dose utilizada para os diferentes polimorfismos (p=0,013). Da mesma forma, para o VKORC1, houve diferença significativa entre a dose e o genótipo (p=0,018). Conclusão: Estes resultados demonstram a necessidade de uma maior assistência a estes pacientes, buscando melhores resultados clínicos, com menos eventos adversos. / Introduction: Warfarin is an oral anticoagulant (OAC) most used in primary health care. With narrow therapeutic window, shows great variability in drug response, and greater susceptibility to adverse events such as bleeding and venous thromboembolism. Among the factors that influence the amount of variability highlights the interactions with both drugs, as with diet and genetic polymorphism. Objectives: To estimate the incidence of adverse events related to warfarin use and describe the user journey through the public health system to the problems. Methods: This is a prospective cohort study conducted over a period of 18 months with users of the public health service in the use of warfarin, the city of Ijuí/RS. The data were collected monthly interviews in homes and complemented with medical information obtained in primary and tertiary care. Drug interactions were checked in databases and eating habits as validated methodology. The statistics used to associate bleeding and Time in Therapeutic Range (TTR) and the risk factors was Poison test. The project was approved by the Research Ethics Committee of UFRGS, with opinion number 336259/2013. Results: We interviewed and followed 69 patients, 64 completed the follow-up and 5 died during the study, 55.1% were female, mean age 64.3 ± 13.7 years. The mean duration of warfarin use was 5.5 years, the average weekly dose was 30.69 ± 15,19mg and the main reason for warfarin use was valvular prosthesis (39.7%). The average per user used medications was 9.6 ± 4.5. As for events, the bleeding had incidence of 37.7 / 100 patients / year, thromboembolism of 4.8 / 100 patients / year and deaths of 4.8 / 100 patients / year. Bleeds were associated with having more than three drug interactions with warfarin (p = 0.048) and use of self-medication by drugs (p = 0.030). As for the TTR was no association with age less than 65 years (p = 0.032). And 67 users were susceptible to medicamentosasas interactions with warfarin, with a predominance of moderate, with an average of interactions with this drug of 2.91 ± 1.52. Most interactions acting on the anticoagulant effect of warfarin, increasing the probability of bleeding. Among the interactions that users had, at the time of bleeding, the most common were with: omeprazole, simvastatin and acetaminophen. Most respondents showed low consumption of vitamin K. It was found that bleeding and venous thromboembolism were more frequent in patients starting treatment. And all patients who died during follow-up (5) were patients with more than one year of warfarin use. For adverse event resolution in most cases the patient underwent home care (53.4%), followed by search for the Basic Health Units, 7 patients sought emergency services and 5 held hospitalization. It was observed that approximately half of the patients showed their INR test (International Normalized Ratio) to the doctor. And in the absence of warfarin in public municipal health, which occurred between the months 13:16, from 24.9 to 43.5% stopped using the drug. The polymorphism results demonstrate that 47 (71.2%) did not have the polymorphism CYP2C9 genotype, and 24 (36.4%) the VKORC1 genotype. Evaluating the two genotypes associated, it is found that 17 (25.8%) did not show any polymorphism thereof. There was no statistical association of the polymorphism with gender and race. A significant difference between the dose for different polymorphisms (p = 0.013). Likewise, for the VKORC1, a significant difference between the dose and genotype (p = 0.018). Conclusion: These results demonstrate the need for further assistance to these patients, looking for better clinical outcomes, with fewer adverse events.