The influence of feeding and gastroprotectant medications on the Factor Xa inhibitory activity of orally administered rivaroxaban in normal dogs

OBJECTIVE: Rivaroxaban is a new anticoagulant option for dogs, yet its reported oral bioavailability is as low as 60%. The objective of this study was to examine the influence of feeding and gastroprotectant medications on the bioactivity (anti‐Xa activity) of rivaroxaban in healthy dogs. DESIGN: Prospective experimental study. SETTING: University research laboratory. ANIMALS: Five healthy neutered male purpose‐bred Beagles. INTERVENTIONS: Dogs were administered a median dose of 1.8 mg/kg rivaroxaban (range, 1.6‐1.8 mg/kg) orally once daily for 2 consecutive days with either (1) no food, (2) food, (3) sucralfate 30 minutes before rivaroxaban, or (4) omeprazole at the same time as rivaroxaban. Blood was collected from preplaced jugular catheters immediately before and at 6 time points after rivaroxaban administration (2, 4, 8, 24, 36, and 48 hours). A rivaroxaban calibrated anti‐Xa activity assay (RIVA) was used to monitor anticoagulant effect. MEASUREMENTS AND MAIN RESULTS: Rivaroxaban administration resulted in significant increases in RIVA (P = 0.02), with peak activities occurring 2 to 4 hours after dosingduring each study arm. No feeding was associated with significantly higher RIVA at the 36‐hour time point compared to all other treatment arms (P