Pharmacokinetics and Biologic Activity of Apixaban in Healthy Dogs

Noelle D Herrera; Ingvild Birschmann; Monika Wolny; Mark G Papich; Marjory B Brooks; Robert Goggs

doi:10.3389/fvets.2021.702821

Pharmacokinetics and Biologic Activity of Apixaban in Healthy Dogs

Front Vet Sci. 2021 Jul 5:8:702821. doi: 10.3389/fvets.2021.702821. eCollection 2021.

Authors

Noelle D Herrera¹, Ingvild Birschmann², Monika Wolny², Mark G Papich³, Marjory B Brooks⁴, Robert Goggs¹

Affiliations

¹ Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, United States.
² Institute for Laboratory and Transfusion Medicine, Heart and Diabetes Center North Rhine-Westphalia, Bad Oeynhausen, Germany.
³ Department of Molecular Biomedical Sciences, North Carolina State College of Veterinary Medicine, Raleigh, NC, United States.
⁴ Department of Population Medicine and Diagnostic Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, United States.

Abstract

Thrombosis is common in critically ill dogs and causes considerable morbidity and mortality. The direct factor Xa inhibitor apixaban is safe, efficacious, and convenient in humans. This study aimed to determine the pharmacokinetics (PK), bioactivity, protein binding, and bioavailability of apixaban following intravenous (IV) and oral (PO) administration to healthy dogs. Six healthy, adult, mixed-breed dogs were administered apixaban 0.18 mg/kg IV and then following a minimum 2-week washout period administered apixaban 0.2 mg/kg PO. Dogs were monitored using an apixaban-calibrated anti-Xa bioassay, prothrombin time (PT) and activated partial thromboplastin time (aPTT) and tissue-factor thromboelastography (TF-TEG). Plasma apixaban concentrations were measured using liquid chromatography-tandem mass spectrometry. Concentration-time plots were constructed, and PK modeling performed using compartmental methods. Administration of IV and PO apixaban was well-tolerated. Following IV administration, mean half-life was 4.1 h, and volume of distribution was 177 ml/kg. Apixaban was highly protein bound (98.6%). Apixaban concentrations and anti-Xa activity were highly correlated (R² 0.994, P < 0.0001). Intravenous apixaban significantly prolonged PT at time points up to 1 h, and aPTT at time points up to 0.25 h post-administration. Coagulation times were positively correlated with apixaban concentrations (PT R² 0.599, P < 0.0001; aPTT R² 0.430, P < 0.0001) and TF-TEG R-time was significantly prolonged 0.25 h post-administration. Following oral administration, mean bioavailability was 28.4%, lag time was 2 h, time to C_max was 5 h and the apparent elimination half-life was 3.1 h. Oral apixaban significantly prolonged PT at 4, 6, and 8 h but aPTT and TF-TEG were not consistently affected by oral apixaban. Apixaban concentrations are best monitored using anti-Xa activity. Future studies should determine PK and bioactivity of other doses using commercial tablets and following multidose administration and establish safe, effective dosing ranges in sick dogs.

Keywords: anti-Xa activity; antithrombotic; direct oral anticoagulant; thromboelastography; thrombosis.