453Use of Non-vitamin K antagonist Oral Anticoagulants in a real-world setting: a community pharmacy-based study
Authors: Capiau A , Mehuys E , Van Tongelen I , De Backer T , Christiaens T , De Sutter A , Steurbaut S , Moudallel S , Rydant S , Boussery K 
Published: October 2019

Abstract

Background
The emergence of non-vitamin K antagonist oral anticoagulants (NOAC) has caused a paradigm shift in anticoagulation therapy, with NOAC being increasingly used compared to vitamin K antagonists. Despite the numerous RCTs with NOAC, further follow-up on how this high risk new drug class is used in real-world clinical practice is warranted.

Purpose
This study aimed to describe NOAC use in a primary care sample of long-term NOAC users, and investigated (i) adherence, (ii) patients' perceptions, (iii) drug interactions and (iv) appropriateness of dosing.

Methods
A cross-sectional observational study was conducted in 158 community pharmacies. Participants were home-dwelling adults treated with a NOAC for at least one year. They completed a questionnaire collecting data on socio-demographics, clinical characteristics, current medication use, self-reported adherence to NOAC (via Medication Adherence Report Scale, MARS), and beliefs and perceptions about NOAC (via Beliefs about Medicines Questionnaire, BMQ). Adherence to NOAC (self-reported (MARS) and calculated using pharmacy dispensing data (Medication Possession Ratio (MPR)); patients' beliefs and perceptions about NOAC (BMQ); and prevalence of drug interactions and inappropriate dosing (using the recommendations in the summary of product characteristics (SmPC) and the 2018 European Heart Rhythm Association (EHRA) Practical Guide) were assessed.

Results
Participants (n=766) had a mean age of 76.2±8.8 years, several co-morbidities (median of 5 (IQR 4–6)) and high thromboembolic risk (median CHA2DS2-VASc score of 4 (IQR 3–4)). The majority (93.5%) used NOAC for non-valvular atrial fibrillation, while the other 6.5% used it for the prevention of recurrent deep vein thrombosis or pulmonary embolism. Forty point five percent of the study sample used rivaroxaban, 36.2% apixaban, 21.1% dabigatran and 2.2% edoxaban. About 85% was adherent according to MPR (MPR ≥80%) and self-reported adherence was also high (mean MARS score 24.6±1.0). Two-thirds reported at least one adverse event of the NOAC, with easy bruising/bleeding being most prevalent (40.2% of patients). BMQ showed that 91.3% of patients favoured the “necessity” over the “concerns” of NOAC use. Thirty-one percent of patients had ≥1 drug interaction(s) with NOAC; amiodarone (10.4% of patients), antiplatelet agents (9.7%) and NSAIDs (9.0%) were the most common interacting drugs. NOAC dosing was inappropriate in 15.9% of patients according to SmPC and in 23.1% according to EHRA. Intriguingly, underdosing was more common using the SmPC as reference, while overdosing was more common using the EHRA guideline.

Conclusions
This real-world analysis of NOAC use revealed high adherence and necessity beliefs, drug interactions in 30% of patients, and suboptimal dosing in about one fifth of patients. These findings can inform the design of targeted community pharmacist interventions to improve quality of NOAC use.