Medication Adherence to Direct Oral Anticoagulants: Extent and Impact of Side Effects

Abstract

Purpose Arterial and venous thromboembolism are a leading cause of mortality. Direct oral anticoagulants (DOACs) are highly effective in both stroke prevention and prevention of venous thrombotic events. Medication adherence is a prerequisite for optimal protection against thromboembolic complications. Recent studies have shown that good adherence cannot be taken for granted by DOACs. In this cross-sectional study adherence among DOAC users was investigated and associations between beliefs about medication, perceived side effects and adherence were explored. Patients and Methods We included 100 randomly selected adult DOAC users visiting one of the two participating Dutch community pharmacies in the summer of 2020. The self-reported adherence (primary outcome) was assessed with the Medication Adherence Rating Scale-5 (MARS-5) using three different cut-off scores. Beliefs about DOACs were assessed with the Beliefs about Medicine Questionnaire Specific (BMQ-S), while side effects and side effect burden were assessed with a self-developed questionnaire based on the Lareb Intensive Monitoring (LIM) system. Results Of the participants, 9% reported non-adherence on the primary MARS-5 cut-off score <24. For the MARS-5 scores <23 and <25 non-adherence percentages of, respectively, 3 and 33% were calculated. Associations were found between adherence and both side effects and side effect burden, regardless of the MARS-5 cut-off score. Bruising and minor bleeds were the most reported side effects (both 20%). For all patients, the necessity beliefs outweighed the concern beliefs. No associations were found between adherence and either gender, indication, DOAC or dosage. Conclusion This study confirms that adherence in patients on DOACs cannot be taken for granted. High necessity beliefs do not guarantee good adherence, as side effects impair adherence even in patients having high necessity beliefs. Therefore, we recommend that both physicians and pharmacists evaluate both adherence and side effects with these patients on a regular base.