Warfarin is an oral anticoagulant widely used for primary and secondary prevention of thromboembolism that belongs to the class of vitamin K antagonists.^, In Brazil, warfarin is still the main oral anticoagulant distributed free of charge by the Unified Health System. According to the Institute for Safe Practices in the Use of Medicines (ISMP – Brazil), warfarin is classified as a high-alert or potentially dangerous drug since it has a low therapeutic index and its use requires constant attention for the drug to act in the prevention of thromboembolic events without increasing the risk of hemorrhages.^, Furthermore, it appears as one of the drugs that should be the target of priority actions for the prevention of damage, according to the Third Global Patient Safety Challenge of the World Health Organization Health.

Management of anticoagulant therapy with warfarin is a challenge for many patients. It requires procedures that are considered complex, such as the regular measurement of the international normalized ratio (INR), the interpretation of the results to adjust the drug dose by the responsible team, as well as the adequate understanding of the factors that may influence its effectiveness and safety, such as adverse reactions and interactions with other drugs and foods.^, Thus, strategies are needed to help in the proper and safe use of the medication and contribute to understanding its use process and consequent adherence to treatment.

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