ABSTRACT
Abstract Background Warfarin is the only oral anticoagulant available in the Brazilian public health system. Health knowledge and treatment are essential to achieving the desirable therapeutic effect. However, data on these aspects among primary care patients are still lacking. Objective To assess health literacy, patient knowledge, and adherence to oral anticoagulation with warfarin, as well as the medication regimen complexity in primary health units in the municipality of Divinópolis, Minas Gerais, Brazil. Methods This cross-sectional study included patients using warfarin from primary care settings. Sociodemographic and clinical data were collected from medical records. Short Assessment of Health Literacy for Portuguese-Speaking Adults (SAHLPA-18), Oral Anticoagulation Knowledge (OAK), adaptation of the Measure of Adherence to Treatment (MAT-adapted) to oral anticoagulation, and Medication Regimen Complexity Index (MRCI) were applied, and the time in therapeutic range (TTR) was calculated. Patients were stratified in two groups (TTR < 60% and TTR ≥ 60%) and compared using Fisher's exact test at a significance level of p < 0.050. Results Analysis included 162 patients (64.8 ± 12.7 years old, 55.6% women). Nonvalvular atrial fibrillation (26.5%) and venous thromboembolism (24.1%) were the main indications for warfarin, and 67.9%, 88.3%, and 16.7% of the patients had inadequate health literacy, insufficient knowledge regarding anticoagulant therapy, and non-adherence to warfarin therapy, respectively. There was no significant association of these parameters in relation to TTR. MRCI showed high pharmacotherapy complexity between the drug prescriptions. Conclusion This study showed alarming insufficient knowledge about warfarin therapy and low health literacy in primary care patients.