2015 ACVIM Forum Research Abstract Program

Apixaban had a predictable inhibitory effect on FXa activity in all cats resulting in FXa activity within the therapeutic range (11-42% compared to baseline) used in human patients. This range corresponds to a therapeutic international normalized ratio (2.0-3.5) and was noted in all cats at multiple time points. Furthermore, PD data in these cats showed cyclical inhibition of FXa activity that is typical of novel oral anticoagulant drugs and a property that is considered important for their safety profile. PK data from this pilot study showed a lack of drug accumulation and a consistent elimination half-life between the first and last oral doses at approximately 2.5 hours. The cyclical inhibition of FXa activity appeared to correlate directly with plasma concentration-time curves. One cat became lethargic and vomited once on day 3 and was removed from the study. Interestingly, while peak plasma concentrations in this cat were not significantly different, trough concentrations were on average 3-fold higher. This cat's signs resolved after discontinuing the drug. Bleeding was not noted in any cat.