Effects of systemic administrations of medetomidine and xylazine on ex vivo platelet aggregation in clinically normal cats

Abstract

This study aimed to investigate and compare the effects of systemic administration of medetomidine and xylazine
on ex vivo platelet aggregation in clinically normal cats. Five cats were repeatedly used in each of 7 groups. The cats
received saline as the non-medicated control; 0.5, 2.0, and 4.0 mg/kg xylazine; and 20, 80, and 160 μg/kg BW
medetomidine intramuscularly. Venous blood was collected 4 times (0, 2, 4, and 7 h) after injection of both agents and
platelet-rich plasma was prepared. Ex vivo percent platelet aggregation was determined via a turbidimetric method.
Collagen and adenosine diphosphate (ADP) were used to initiate aggregation. Administrations of xylazine at all
dosages did not significantly change the platelet aggregation induced by ADP and collagen compared with the control.
In contrast, administration of medetomidine at 80 μg/kg significantly reduced platelet aggregation induced by both
ADP and collagen compared with the control, whereas medetomidine at the other dosages did not significantly change
the platelet aggregation induced by ADP and collagen. These results indicate that systemic administration of xylazine
can be used in feline practice without concern for adverse effects on platelet function, although, if medetomidine is
used, even in limited dosages, it may inhibit platelet aggregation.