A Retrospective Evaluation of the Appropriateness of Non-Vitamin K Antagonist Oral Anticoagulants (NOAC) Prescribing in Out-Patients at Prapokklao Hospital

Abstract

Background: Non-vitamin K antagonist oral anticoagulants (NOACs) are increasingly used as alternative to Warfarin because they do not require routine international normalized ratio (INR) monitoring and are less affected by dietary vitamin K intake. However, appropriate NOAC use requires careful consideration of approved indications, dosing regimens, renal function, drug-drug interactions, and anticoagulant switching patterns to prevent adverse clinical outcomes.

Objectives: To evaluate the patterns and appropriateness of NOAC use regarding approved indications, dosing regimens, and anticoagulant switching among outpatients.

Methods: A retrospective, descriptive study was performed through the analysis of electronic medical records. A total of 359 outpatients who received Dabigatran, Rivaroxaban, and Apixaban at Prapokklao Hospital between 1 January 2017 and 31 December 2023 were included. Data were analyzed using descriptive statistics. The appropriateness of NOAC was assessed based on indication, renal function, age, body weight, and potential drug-drug interactions.

Results: Rivaroxaban was the most commonly prescribed NOACs at 49.58%. Regarding the appropriateness of prescribing according to approved indications by Thai Food and Drug Administration, the primary indication was stroke prevention in patients with non-valvular atrial fibrillation by 84.68%, followed by treatment of venous thromboembolism at 9.47%, while 5.88% of prescriptions were considered inappropriate indications. Dabigatran demonstrated the highest proportion of appropriate dosing at 65.88%, whereas Apixaban showed the highest rate of overdosing by 18.75%. Potential drug-drug interactions were identified in 20.6% of patients, most commonly with Antiplatelet agents. In addition, 22.35% to 38.76% of patients could not be evaluated for dosing appropriateness due to missing renal function data in the medical records. Thirty patients underwent anticoagulant switching, of whom at 93.33% were considered appropriate, including switching from Warfarin to NOACs when INR was ≤ 2.2 or switching between NOACs according to clinical indications.

Conclusions: Most NOAC use was consistent with approved indications. However, inappropriate dosing, particularly overdosing with Apixaban, and incomplete renal function monitoring were identified. Strengthening clinical decision support systems and enhanced pharmacist involvement may improve the safety and appropriateness of NOAC use.