Anticoagulant poisoning in dogs

Poisoning with anticoagulants (rat poison, antivitamin K rodenticides) is the leading cause of intoxication in dogs (3rd in cats). This statement is according to the national toxicological information centers (CNITV and CAPAE Ouest). The ingestion of these toxicants causes hemorrhagic phenomena. It means that to say internal or external blood loss which can lead to the death of the animal. The early detection of this type of intoxication is essential; it requires a rigorous diagnostic process to set up, as quickly as possible, a specifically adapted treatment. Here, you will know about anticoagulant poisoning in dogs.

Mechanisms of hemostasis

There is, within the body, a physiological phenomenon allowing the control of hemorrhages and the stopping of bleeding: it is called hemostasis.

This hemostasis is split into two main successive stages, which link together very quickly:

  • Primary hemostasis: following a vascular breach, vasoconstriction (reduction in the diameter of the vessel) occurs as well as the formation of an unstable “clot” consisting essentially of aggregated blood platelets (or thrombocytes): this clot is called a “platelet nail”. An important blood protein, the von Willebrand factor involves during this stage;
  • Secondary hemostasis (or coagulation): during this stage, many reactions are linked in a cascade between several plasma proteins (13), called coagulation factors. These reactions result in the formation of an insoluble protein, fibrin, which will stabilize and consolidate the platelet nail: a clot is thus formed. The bleeding will stop.

The liver involves in the manufacture of many coagulation factors. Among them, factors II, VII, IX, and X need vitamin K1 to make and activate to become functional.

In the absence of vitamin K1, factors II, VII, IX, and X cannot correctly synthesize and activated; then a solid clot cannot form, the vascular breach cannot fill and the bleeding continues.

Mode of action of rodenticides

Vitamin K (AVK) rodenticides inhibit an enzyme in the body called epoxide reductase. The latter is essential because it makes it possible to obtain Vitamin K1 in reduced form. It is a form that activates factors II, VII, IX, and X so that they are functional. Thus, without epoxide reductase, active coagulation factors are not available and secondary hemostasis cannot be achieved properly.

It is important to note that there is initially, in the liver, a stock of reduced thus functional vitamin K1. These reserves will gradually consume before disappearing completely. This reduced vitamin K1 stock explains the delay that can exist between ingestion of AVK rodenticides & the onset of symptoms.


The symptoms triggers only 48 hours after ingestion of rodenticides (after consumption of the vitamin K1 stock). It is what is insidious with this type of intoxication.

The bleeding that appears can be easy to identify: hematoma, nasal bleeding (epistaxis), mouth or eye (hyphema), blood in the urine (hematuria) or the stool (melena), vulvar hemorrhagic discharge mimicking heat in the woman. female (metrorrhagia).

But the bleeding is sometimes internal and can be more difficult to identify: cough or breathing difficulties (if pulmonary bleeding), lameness (hemarthrosis), abdominal dilation (blood effusion), or, more rarely, neurological disorders (during cerebral hemorrhages) for example).

In all cases, certain discreet symptoms should look for: pale mucous membranes (gums, ocular conjunctiva), petechiae (small hemorrhagic points on the mucous membranes or the skin), any cutaneous or subcutaneous swelling.

Anticoagulant poisoning in dogs


The diagnosis requires highlighting a coagulation disorder (secondary hemostasis). For it, the veterinarian takes a blood test to carry out the coagulation times. It is common as prothrombin time and activated cephalin time. During intoxication by AVK rodenticides, the coagulation times increases (unless ingestion took place within the last 48 hours).

The veterinarian may perform other additional examinations (ultrasound, X-ray, and additional blood tests) to assess any complications caused by the bleeding.

It is possibly possible to identify the molecule ingested thanks to a toxicological analysis by a specialized laboratory: this can help concerning the duration of the treatment (see below) because the AVK rodenticides have different durations of action, more or less long.

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Treatment of anticoagulant poisoning in dogs

The treatment of intoxication with anticoagulants requires the use of an antidote. This antidote is vitamin K1 at a dose of 5 mg/kg/day, initially intravenously and then orally.

Depending on the anti-vitamin K molecule involved, the duration of treatment may be 1 week (1st generation molecules), 1 month (2nd generation), or even several months (3rd generation).

In general, a treatment of 3 weeks will recommend. A determination of the coagulation times 48 hours after the end of the treatment will carry out. If the latter is still high, 3 additional weeks of treatment will prescribe.

In some cases, more intensive treatment may be necessary: ​​infusion, transfusion of fresh blood, oxygenation, etc.

In cases where the ingestion of the toxic product has observe. It is important to go to the veterinarian as quickly as possible. In fact, within 4 to 6 hours after ingestion, it is possible to induce vomiting. ‘Animals and administer a digestive bandage to reduce the risk of assimilation of the toxicant. This can help avoid treatment for several weeks. A blood test will then be carried out after 48 hours to evaluate the coagulation times and verify that intoxication has been avoided.


The prognosis is generally excellent when treatment is rapid. It is more reserved during complications or late diagnosis.


When using anticoagulant rat poison in your home, it is important to take into account the risk you take, our pets, by their research instincts, their sense of smell, … regularly manage to access these toxic. To avoid this, consider using bait box systems to ensure the safety of our companions; possibly use trapping systems.

Finally, we must keep in mind the insidious aspect of this type of intoxication: in fact, the onset of symptoms will postpone for several days compared to the ingestion of the toxicant.