Assessing Methods to Monitor Rivaroxaban Therapy and the Viability of the Calibrated Automated Thrombogram (CAT) using Low Plasma Volumes in Dogs

Journal Title
Journal ISSN
Volume Title
University of Guelph

Hypercoagulability, thrombosis, and the use of anti-thrombotic drugs in companion animals are important areas of research in veterinary medicine. There is a paucity of information regarding dosing, effect, and monitoring of anti-thrombotic drugs, such as rivaroxaban, in clinically ill animals.

In the first study, 12 client-owned dogs diagnosed with hypercoagulability and/or thromboembolic disease and prescribed rivaroxaban, were recruited. Blood samples were collected prior to treatment, then 1-week and 1 to 3-months after initiation of therapy. The hemostatic tests prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, rivaroxaban specific anti-Xa assay (raXa), thromboelastography (TEG) with strong activators, and thrombin generation (TG) were performed at each visit (3 hours after rivaroxaban dosing). There was a strong correlation between raXa and PT (p<0.001). The raXa was strongly positively correlated with TG variables- time to peak (ttpeak, p<0.001) and lag time (lag time, p<0.001), and negatively correlated with TG variables- endogenous thrombin potential (ETP, p<0.001) and peak (peak, p<0.001). There was poor correlation between raXa and aPTT, fibrinogen, and all TEG variables.

In the second study, archived plasma samples from dogs previously determined to have low (hypocoagulable, n=10), normal (n=10), and high (hypercoagulable, n=10) thrombin generation potential were used. Method comparison was performed for the calibrated automated thrombogram (CAT) using standard (80 μL plasma, 20 μL reagent- method 1) and low volume (40 μL plasma, 10 μL reagent- method 2) plasma and reagent, respectively. Four parameters of the TG curve were assessed: lag time; ETP; peak; and ttpeak. There was excellent agreement between methods 1 and 2 for all parameters.

In conclusion, PT and TG were found to strongly correlate with raXa and may be a convenient method to monitor hypercoagulable dogs receiving rivaroxaban therapy. Additionally, low volume CAT appears to be a valid alternative to the standard testing method in dogs with a range of thrombin generation potentials.

rivaroxaban, dog, thrombin generation, prothrombin time