Patient adherence to rivaroxaban in deep vein thrombosis, a cohort study in Switzerland: quantitative results

Background Direct oral anticoagulants (DOACs) have the advantage of being administered orally at a fixed dose without laboratory monitoring, in contrast to the frequent international normalized ratio measurements used to adjust for vitamin K antagonists dosing. Rivaroxaban, has a short half-life. The anticoagulation effect rapidly decreases if medication adherence is suboptimal. Objective The purpose of this quantitative study (called RIVA) is to longitudinally describe adherence to rivaroxaban (implementation and persistence) in patients with deep vein thrombosis (DVT). Setting The community pharmacy of the Center for Primary Care and Public Health (Unisanté), University of Lausanne, Switzerland in collaboration with the angiology division of the Lausanne University Hospital (CHUV). Methods This is an observational study. Patients received rivaroxaban for 3 or 6 months: 15 mg twice a day during the first 3 weeks and then 20 mg once a day until the end of the treatment. Adherence was measured using electronic monitoring. Implementation and adherence were modelled using a generalized estimating equation model. Persistence was represented using a Kaplan-Meier survival curve. Main outcome measure Medication adherence (implementation and persistence). Results Thirty-one consecutive patients were included (68% male, mean age: 47 years old). The collected adherence data consisted of 57 inter-visit phases, 2899 electronic monitoring openings and a median follow-up of 92 days (IQR: 87; 100). Implementation to rivaroxaban was initially high [96.3 (92.8; 98.1)] but decreased during the first 3 weeks, until it reached 89.3 (76.0; 95.6). After the switch from twice a day 15 mg to a once a day 20 mg regimen, implementation increased again and remained stable [95.4 (92.2; 97.3)] for 90 days. Four patients who experienced adverse events discontinued the treatment before the end of the study and were considered non-persistent (clinically appropriate discontinuation). Conclusion Adherence to rivaroxaban in deep vein trombosis is high in persistent patients. Discontinuation is related to rivaroxaban adverse effects/toxicity. Implementation should be reinforced during the twice a day-phase, and this first 3-week experience should help patients and healthcare professionals choose the best timing for the once a day phase.