Abstract Number: PB2082
Meeting: ISTH 2020 Congress
Theme: Venous Thromboembolism and Cardioembolism » Atrial Fibrillation
Background: Direct oral anticoagulants (DOAC) are increasingly prescribed in older adults with non-valvular atrial fibrillation (NVAF). However, inadequate low doses are frequently used. In Belgium, 43% of DOAC patients are treated with a reduced dose, much more than observed in phase III trials.
Aims: This study aimed at investigating the impact of inadequate low DOAC doses on plasma drug levels in older NVAF patients.
Methods: We performed a retrospective analysis of electronic medical records (2012-2018). Older NVAF patients (≥ 75 years) treated with apixaban, rivaroxaban or dabigatran etexilate and who underwent DOAC measurement at peak or trough were included. DOAC plasma levels were compared between 2 groups (appropriate dose vs inappropriate low dose), and to the on-therapy ranges observed in pivotal trials.
Results: This analysis included 80 patients (median age [IQR] 81 [77-85]), treated with apixaban (n=33), dabigatran etexilate (n=18) and rivaroxaban (n=29). DOAC dosing was appropriate for 54 patients (68%). Eighteen patients (23%) were receiving an inappropriate low dose (table 1).
Appropriate dose (n [%]) | Inappropriate low dose (n [%]) | Inappropriate high dose (n [%]) | TOTAL (n) | |
Apixaban | 21 [64] | 9 [27] | 3 [9] | 33 |
Dabigatran etexilate | 18 [100] | 0 [0] | 0 [0] | 18 |
Rivaroxaban | 15 [52] | 9 [31] | 5 [17] | 29 |
All DOACs | 54 [68] | 18 [23] | 8 [10] | 80 |
[Appropriateness of dosing according to DOAC]
In total, 152 DOAC measurements were performed (figure 1). At peak, mean apixaban and rivaroxaban levels were significantly lower for “inappropriate low dose” patients compared to “appropriate dose” patients (p=0.0092 and 0.0090 respectively). At trough, mean DOAC plasma levels did not differ between groups.
Four (16%) peak and one (7%) trough measurements were under the expected range for “inappropriate low dose” patients. On the contrary, 24 (39%) peak and 7 (18%) trough measurements were above the expected range for “appropriate dose” patients.
Conclusions: Apixaban and rivaroxaban were frequently prescribed at an inappropriate low dose in older NVAF patients. However, most underdosed patients had DOAC levels within the expected on-therapy range. Moreover, a high proportion of patients with an appropriate dose had higher-than-expected peak levels. This raises questions about the optimal DOAC regimen in real-life older patients.
[Figure 1: DOAC plasma levels according to the appropriateness of dosing]
To cite this abstract in AMA style:
Comans A-, Regnier M, Bihin B, Mullier F, de Saint-Hubert M, Sennesael A-. Inappropriate Dosing of Direct Oral Anticoagulants in Older Patients with Non-Valvular Atrial Fibrillation: Impact on Plasma Drug Levels [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/inappropriate-dosing-of-direct-oral-anticoagulants-in-older-patients-with-non-valvular-atrial-fibrillation-impact-on-plasma-drug-levels/. Accessed March 21, 2024.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/inappropriate-dosing-of-direct-oral-anticoagulants-in-older-patients-with-non-valvular-atrial-fibrillation-impact-on-plasma-drug-levels/