Line 38:
Line 38:
during the coagulation process and thus cannot
during the coagulation process and thus cannot
actively participate in fibrin formation.
actively participate in fibrin formation.
+
+
+
Warfarin and similar compounds interfere with the regeneration of vitamin K from an intermediate formed during the action
+
of vitamin K as an essential co-factor in the production of several of the factors involved in the clotting cascade. This is by competitive
+
inhibition of the enzyme involved in the regenerative process and leads to a reduction in available vitamin K, thereby resulting
+
in defective blood clotting. Vitamin K dependent clotting factors are VII, IX, 11 and X so the intrinsic pathway (activated by blood
+
vessel injury), the extrinsic pathway (activated by tissue injury) and the final common pathway (with conversion of prothrombin
+
to thrombin, formation of fibrin and stabilisation of the platelets) is affected. However, the primary haemostatic response (formation
+
of platelet plug) is unaffected.
+
Increased blood vessel fragility also appears to be a result of coumarin toxicity and may account for bleeding at sites that are
+
not subject to external trauma.
+
Following absorption, coumarins are carried bound to plasma albumin. Therefore, effects are potentiated by drugs that are also
+
bound to albumin such as phenylbutazone, or conditions that result in low plasma albumin levels such as renal insufficiency.
==Signalment==
==Signalment==