Protocol for Improvement of Therapy With Warfarin

Atrial Fibrillation (AF) is the most common supraventricular arrhythmia in clinical practice. The presence of AF, as an independent factor, increases mortality by up to two times. One in every six cerebrovascular accidents (CVA) occurs in patients with AF, generating an annual risk of around 7% per year, which represents an increase of up to seven times in relation to the risk in the general population, leading to the need for start anticoagulant therapy. Warfarin is still the Oral Anticoagulant (OC) of choice, being the most used in several clinical situations. The variability of response to anticoagulants is related to pharmacokinetic and pharmacodynamic factors, adherence to treatment, age, diet, body mass index (BMI), liver function, body deposition of vitamin K, individual drug metabolism, drug interactions, comorbidities, in addition to of genetic factors. It is estimated that the annual risks associated with the use of OCs are between 2% and 8% for bleeding. The clinical benefit and risk of OAC therapy are associated with the time in which the values of therapeutic - TTR (time in therapeutic range). Measuring the quality of anticoagulation assesses whether therapy is being maintained within this range. Increased TTR is associated with a decrease in thromboembolic and/or hemorrhagic events. In the context of OCs, pharmacogenetics is the science that predicts the response to drugs, based on individual genetic markers. By understanding the relationship between the genotype and the response to a drug, pharmacogenomics has the potential to help healthcare professionals to predict the therapeutic dose of warfarin by genotyping patients for several Single Nucleotide Polymorphisms (SNPs) that affect metabolism or sensitivity to warfarin. Therefore, the main objectives of genotype-guided therapy are to improve the safety and efficacy of anticoagulant therapy. In Brazil, more specifically in the Brazilian Northeast, the use of a dose predictor algorithm is not common,