<p>For prevention and treatment of thrombotic diseases with an anticoagulant drug it is important that an adequate dose is given to avoid occurrence or recurrence of thrombosis, without increasing the risk of bleeding and other adverse events to unacceptable levels. The aim of this thesis was to develop mathematical models that describe the dose-concentration (pharmacokinetic) and concentration-response (pharmacodynamic) relationships of direct thrombin inhibitors, in order to estimate optimal dosages for treatment and long-term secondary prevention of venous thromboembolism (VTE).</p><p>Population pharmacokinetic-pharmacodynamic models were developed, based on data from clinical investigations in healthy volunteers and patients receiving intravenous inogatran, subcutaneous melagatran and/or its oral prodrug ximelagatran. The benefit-risk profiles of different ximelagatran dosages were estimated using clinical utility functions. These functions were based on the probabilities and fatal consequences of thrombosis, bleeding and elevation of the hepatic enzyme alanine aminotransferase (ALAT).</p><p>The studies demonstrate that the pharmacokinetics of melagatran and ximelagatran were predictable and well correlated to renal function. The coagulation marker, activated partial thromboplastin time (APTT), increased non-linearly with increasing thrombin inhibitor plasma concentration. Overall, the systemic melagatran exposure (AUC) and APTT were similarly predictive of thrombosis and bleedings. The identified relationship between the risk of ALAT-elevation and melagatran AUC suggests that the incidence approaches a maximum at high exposures. The estimated clinical utility was favourable compared to placebo in the overall study population and in special subgroups of patients following fixed dosing of ximelagatran for long-term secondary prevention of VTE. Individualized dosing was predicted to add limited clinical benefit in this indication.</p><p>The models developed can be used to support the studied dosage and for selection of alternative dosing strategies that may improve the clinical outcome of ximelagatran treatment. In addition, the models may be extrapolated to aid the dose selection in clinical trials with other direct thrombin inhibitors.</p>

For prevention and treatment of thrombotic diseases with an anticoagulant drug it is important that an adequate dose is given to avoid occurrence or recurrence of thrombosis, without increasing the risk of bleeding and other adverse events to unacceptable levels. The aim of this thesis was to develop mathematical models that describe the dose-concentration (pharmacokinetic) and concentration-response (pharmacodynamic) relationships of direct thrombin inhibitors, in order to estimate optimal dosages for treatment and long-term secondary prevention of venous thromboembolism (VTE). Population pharmacokinetic-pharmacodynamic models were developed, based on data from clinical investigations in healthy volunteers and patients receiving intravenous inogatran, subcutaneous melagatran and/or its oral prodrug ximelagatran. The benefit-risk profiles of different ximelagatran dosages were estimated using clinical utility functions. These functions were based on the probabilities and fatal consequences of thrombosis, bleeding and elevation of the hepatic enzyme alanine aminotransferase (ALAT). The studies demonstrate that the pharmacokinetics of melagatran and ximelagatran were predictable and well correlated to renal function. The coagulation marker, activated partial thromboplastin time (APTT), increased non-linearly with increasing thrombin inhibitor plasma concentration. Overall, the systemic melagatran exposure (AUC) and APTT were similarly predictive of thrombosis and bleedings. The identified relationship between the risk of ALAT-elevation and melagatran AUC suggests that the incidence approaches a maximum at high exposures. The estimated clinical utility was favourable compared to placebo in the overall study population and in special subgroups of patients following fixed dosing of ximelagatran for long-term secondary prevention of VTE. Individualized dosing was predicted to add limited clinical benefit in this indication. The models developed can be used to support the studied dosage and for selection of alternative dosing strategies that may improve the clinical outcome of ximelagatran treatment. In addition, the models may be extrapolated to aid the dose selection in clinical trials with other direct thrombin inhibitors.

Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-05T11:37:07Z No. of bitstreams: 1 arquivototal.pdf: 12321568 bytes, checksum: e2f13c138059f4c0542b89fde505f812 (MD5) / Made available in DSpace on 2017-09-05T11:37:07Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 12321568 bytes, checksum: e2f13c138059f4c0542b89fde505f812 (MD5) Previous issue date: 2017-03-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Snakebites (Ophidism) are listed by the World Health Organization as a neglected tropical disease and are considered a public health problem. Among the activities triggered by envenoming from Crotalus durissus terrificus snake venom, the coagulant one is intriguing and contradictory, curious and contradictory, since the venom has, in its composition, coagulation precursor proteins and anticoagulant proteins. The present work describes, in vitro, the performance of crude venom, protein fractions and purified proteins of Crotalus durissus terrificus venom on the coagulation factors of human plasma secondary hemostasis. The coagulant and / or anticoagulant activity of crude venom, protein fractions and purified proteins were evaluated directly on human citrated plasma. Changes in Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT) were measured with commercial kits. Clots formed in the presence of crude venom, protein fraction # 7 and Gyroxin displayed as a hyaline flexible mass and steady state. The evaluation of the clot formation time in the presence of the protein fractions # 1 to # 6 and isolated proteins (Crotoxin complex, Crotoxin A, Crotoxin B and Crotamine), after the commercial tests (PT and APTT), allowed to infer that these proteins interfere in all pathways of the coagulation cascade. Therefore, the Crotoxin A, Crotoxin B, Crotoxin and Crotamine proteins may act similarly to some anticoagulants direct inhibitors of thrombin, factor Xa and antithrombin III activator. Moreover, Crotoxin B can inhibits the formation of the prothrombinase complex by direct interaction with factor Xa. Consequently, the protein content from C. d. terrificus snake venom can act synergistically in coagulation and dysfunction and / or inhibition of natural anticoagulants unbalancing hemostasis. / Acidentes ofídicos (ofidismo) são listados, pela Organização Mundial de Saúde, como doença tropical negligenciada e são considerados um problema de saúde pública. Dentre as atividades desencadeadas pelo empeçonhamento por Crotalus durissus terrificus, a coagulante é curiosa e contraditória, pois a peçonha apresenta, em sua composição, proteínas precursoras da coagulação e proteínas anticoagulantes. O presente trabalho descreve, in vitro, a atuação da peçonha bruta, de frações proteicas e proteínas purificadas da peçonha de Crotalus durissus terrificus sobre os fatores de coagulação da hemostasia secundária do plasma humano. A atividade coagulante e/ou anticoagulante da peçonha bruta, frações proteicas e proteínas purificadas foram avaliadas diretamente sobre o plasma citratado humano e as alterações no Tempo de Protrombina (TP) e no Tempo de Tromboplastina Parcial Ativada (TTPA) foram aferidos com kits comerciais. Os coágulos formados na presença da peçonha bruta, da fração proteica #7 e da Giroxina apresentaram-se como uma massa hialina de textura flexível e pontual. A avaliação do tempo de formação dos coágulos na presença das frações proteicas #1 até #6 e das proteínas isoladas Crotoxina, Crotoxina A, Crotoxina B e Crotamina, após a aplicação dos testes comerciais (PT e APTT), possibilitou inferir que essas proteínas interferem em todas as vias da cascata de coagulação. Por conseguinte, as proteínas Crotoxina A, Crotoxina B, Crotoxina e Crotamina podem atuar de forma semelhante a alguns anticoagulantes inibidores direto de trombina, do fator Xa e do ativador da antitrombina III. Ainda, a Crotoxina B pode inibir a formação do complexo protrombinase por interação direta com o fator Xa. Consequentemente, o conteúdo proteico da peçonha de C. d. terrificus pode atuar de forma sinérgica na coagulação e na disfunção e/ou inibição dos anticoagulantes naturais desequilibrando a hemostasia.

No description available.