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. 2025 Mar-Apr;39(2):e70014.
doi: 10.1111/jvim.70014.

Monitoring of Rivaroxaban Therapy in Hypercoagulable Dogs

Erin M Phillips  1 , Shauna L Blois  1 , Anthony C G Abrams-Ogg  1 , R Darren Wood  2 , Gabrielle Monteith  1 , Benoît Cuq  3
Affiliations

Monitoring of Rivaroxaban Therapy in Hypercoagulable Dogs

Erin M Phillips et al. J Vet Intern Med. 2025 Mar-Apr.

Abstract

Background: Measurement of rivaroxaban efficacy using the rivaroxaban-specific anti-Xa assay (raXa) can be used for monitoring in veterinary medicine. Detection of rivaroxaban efficacy using other hemostatic tests would make monitoring timelier and more accessible.

Objectives: Compare results of raXa with prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen concentration, tissue factor (TF) and kaolin-activated thromboelastography (TEG), and thrombin generation (TG) in hypercoagulable dogs.

Animals: Twelve client-owned dogs, diagnosed with hypercoagulability or thromboembolic disease, and prescribed rivaroxaban, were recruited from a tertiary referral hospital from 2020 to 2022.

Methods: Prospective clinical trial. Jugular vein blood samples were collected before treatment, and 1 week and 1-3 months after initiation of rivaroxaban therapy. Hemostatic tests were performed at each visit (3 h after rivaroxaban dosing). TG curve parameters lag time, endogenous thrombin potential (ETP), peak, and time to peak (ttpeak) were assessed.

Results: There was a significant linear relationship between raXa and PT (r2 = 0.74, p < 0.001), ETP (r2 = 0.83, p < 0.001), lag time (r2 = 0.87, p < 0.001), peak (r2 = 0.86, p < 0.001), and ttpeak (r2 = 0.86, p < 0.001). There was a weak linear relationship between raXa and kaolin-activated TEG parameter reaction time (R) (r2 = 0.49, p = 0.026). There was no significant relationship between raXa and aPTT, fibrinogen concentration and the remainder of the TEG variables (p > 0.05).

Conclusion and clinical importance: PT and TG correlated with raXa. PT performed at a reference laboratory appeared to be a convenient method to monitor a small cohort of dogs receiving rivaroxaban therapy.

Keywords: anti‐Xa assay; prothrombin time (PT); thrombin generation.

PubMed Disclaimer

Conflict of interest statement

Authors declare no off‐label use of antimicrobials.

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Serial hemostatic test results (PT, ETP, lag time, peak, raXa) in a group of 12 hypercoagulable dogs treated with rivaroxaban. Linear regression model shows a significant linear relationship between raXa and (A) PT (linear slope = 0.3968, r 2 = 0.74, p < 0.001), (B) ETP (linear slope = −0.8129, r 2 = 0.83, p < 0.001), (C) lag time (linear slope = 1.2689, r 2 = 0.87, p < 0.001, (D) peak (linear slope = −0.0188, r 2 = 0.86, p < 0.001). Predicted equations for significant predictors for the model: log raXa = 0.379 (pt) + 0.964, log raXa = −0.018 (peak) + 5.48, log raXa = 1.2689 (lagtime) + 1.42, log raXa = −0.008 (ETP) + 6.05. The blue curved line represents the mean predictive values of each test created using the model, and the black dots are the observed values of each dog for the corresponding tests. The gray curved lines represent the upper and lower confidence interval for each test, and the purple box represents the reference range for raXa. The green horizontal line represents the reference interval for each parameter, and the black vertical lines indicate the upper and lower cut points for each hemostatic test.
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