Brodifacoum is a highly lethal vitamin K antagonist
Vitamin K antagonist
Vitamin K antagonists are a class of anticoagulants. They reduce blood clotting by inhibiting the recycling of vitamin K epoxide back to the active reduced form of vitamin K. The term Vitamin K antagonists is a misnomer. These drugs do NOT antagonize the action of Vitamin K...

An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...

In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

. In recent years, it has become one of the world's most widely used pesticides. It is typically used as a rodenticide but is also used to control larger mammalian pests such as possum
A possum is any of about 70 small to medium-sized arboreal marsupial species native to Australia, New Guinea, and Sulawesi .Possums are quadrupedal diprotodont marsupials with long tails...


Brodifacoum has an especially long half-life in the body, which ranges to several months, requiring prolonged treatment with antidotal vitamin K for both human and pet poisonings.


Brodifacoum is a 4-hydroxycoumarin anticoagulant, with a similar mode of action to its historical predecessors dicoumarol and warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...

. However, due to very high potency and long duration of action (elimination half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of 20 – 130 days), it is characterised as a "second generation" or "superwarfarin" anticoagulant.

Brodifacoum inhibits the enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 Vitamin K epoxide reductase
Vitamin K epoxide reductase
Vitamin K epoxide reductase is an enzyme that reduces vitamin K after it has been oxidised in the carboxylation of glutamic acid. Its C1 subunit is the target of anticoagulant warfarin.- See also :* Oxidoreductase...

. This enzyme is needed for the reconstitution of the vitamin K in its cycle from vitamin K-epoxide, and so brodifacoum steadily decreases the level of active vitamin K in the blood. Vitamin K is required for the synthesis of important substances including prothrombin, which is involved in blood clotting. This disruption becomes increasingly severe until the blood effectively loses any ability to clot.

In addition, brodifacoum (as with other anticoagulants in toxic doses) increases permeability
Vascular permeability
Vascular permeability, often in the form of capillary permeability, characterizes the capacity of a blood vessel wall to allow for the flow of small molecules or even whole cells in and out of the vessel. Blood vessel walls are lined by a single layer of endothelial cells...

 of blood capillaries; the blood plasma and blood itself begins to leak from the smallest blood vessels. A poisoned animal will suffer progressively worsening internal bleeding, leading to shock, loss of consciousness, and eventually death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....


Brodifacoum is highly lethal to mammals and birds, and extremely lethal to fish. It is a highly cumulative
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...

 poison, due to its high lipophilicity and extremely slow elimination
- Science and medicine :*Elimination reaction, an organic reaction in which two functional groups split to form an organic product*Elimination, clearance of a drug or other foreign agent from the body...


Following are acute values for various animals (mammals):
  • rats (oral) 0.27—0.30 mg/kg b.w.
  • mice (oral) 0.40 mg/kg b.w.
  • rabbits (oral) 0.30 mg/kg b.w.
  • guinea-pigs (oral) 0.28 mg/kg b.w.
  • cats (oral) 0.25 mg/kg b.w. (approx.)
  • dogs (oral) 0.25–3.6 mg/kg b.w.

LD50 values for various birds varies from about 1 mg/kg b.w. — 20 mg/kg b.w.

LC50 for fish:
  • trout (96 hours exposure) 0.04 ppm

Given these extremely high toxicities in various mammals, brodifacoum is classified as "extremely toxic" (LD50 < 1.0 mg/kg b.w.) and "very toxic" (T+; LD50 < 25 mg/kg b.w.), respectively. Because of its persistency, cumulative potential and high toxicities for various wildlife species, it is also considered an environmental pollutant (N; noxious to the environment).
The readiness of brodifacoum to penetrate intact skin should be noted, and brodifacoum and commercial preparations containing it should be handled with respective care and precaution because of its skin resorptivity.

The estimated average fatal dose for an adult man (60 kg b.w.) is about 15 mg, without treatment. However, due to low bait concentrations (usually 10 – 50 mg/kg bait, i.e. 0.001 — 0.005%) and slow onset of symptoms, and the existence of a highly effective antidote (appropriately dosed vitamin K1), brodifacoum is considered to be of relatively low hazard to humans. A caveat is that the poisoning must be identified specifically, so that vitamin K supplementation and monitoring may be maintained for periods that range up to months. The same is true for pets which ingest the substance.

Brand names

Brodifacoum is marketed under a large variety of trade names, including Biosnap, d-Con, Finale, Fologorat, Havoc, Jaguar, Klerat, Matikus, Mouser, Pestanal (Sigma-Aldrich BT), Pestoff, Ratak+, Rodend, Ratsak, Talon, Volak, Vertox and Volid.

Treatment for humans

The primary antidote to brodifacoum poisoning is immediate administration of vitamin K1
Vitamin K
Vitamin K is a group of structurally similar, fat soluble vitamins that are needed for the posttranslational modification of certain proteins required for blood coagulation and in metabolic pathways in bone and other tissue. They are 2-methyl-1,4-naphthoquinone derivatives...

 (dosage for humans: initially slow intravenous injections of 10–25 mg repeated all 3–6 hours until normalisation of the prothrombin time; then 10 mg orally four times daily as a "maintenance dose"). It is an extremely effective antidote, provided the poisoning is caught before too much damage has been done to the victim's circulatory system. As high doses of brodifacoum can affect the body for many months, the antidote must be administered regularly for a long period (several months, in keeping with the substance's half-life) with frequent monitoring of the prothrombin time
Prothrombin time
The prothrombin time and its derived measures of prothrombin ratio and international normalized ratio are measures of the extrinsic pathway of coagulation. This test is also called "ProTime INR" and "INR PT". They are used to determine the clotting tendency of blood, in the measure of warfarin...


If unabsorbed poison is still in the digestive system, gastric lavage
Gastric lavage
Gastric lavage, also commonly called stomach pumping or Gastric irrigation, is the process of cleaning out the contents of the stomach. It has been used for over 200 years as a means of eliminating poisons from the stomach. Such devices are normally used on a person who has ingested a poison or...

 followed by administration of activated charcoal may be required.

Further treatments to be considered include infusion of blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 or plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...

 to counteract hypovolemic shock
In physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...

; and in severe cases, infusion of blood clotting factor concentrate.

Administration of vitamin C
Vitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...

 may be useful as an adjunct (100 mg three times daily).

Another potential treatment is phenobarbital
Phenobarbital or phenobarbitone is a barbiturate, first marketed as Luminal by Friedr. Bayer et comp. It is the most widely used anticonvulsant worldwide, and the oldest still commonly used. It also has sedative and hypnotic properties but, as with other barbiturates, has been superseded by the...

, which is believed to accelerate the metabolism of some anticoagulants via enzyme induction
Enzyme induction and inhibition
Enzyme induction is a process in which a molecule induces the expression of an enzyme.Enzyme inhibition can refer to* the inhibition of the expression of the enzyme by another molecule...


Poisoning case reports

There have been at least ten case reports of brodifacoum intoxication in the medical literature.

In one report, a woman deliberately consumed over 1.5 kilograms of rat bait, constituting about 75 mg brodifacoum, but made a full recovery after receiving conventional medical treatment.

In another report, a 17-year-old boy presented to the hospital with a severe bleeding disorder. It was discovered that he habitually smoked a mixture of brodifacoum and marijuana. Despite treatment with vitamin K, the bleeding disorder persisted for several months. He eventually recovered.

Environmental toxicology

The American Bird Conservancy
American Bird Conservancy
American Bird Conservancy is a non-profit membership organization with the mission of conserving native birds and their habitats throughout the Americas...

has advocated that brodifacoum not be used by the general public. They cite several studies indicating that secondary poisonings of predatory birds and animals are common due to the extreme persistence of the pesticide within both target and non-target species. It may also be dispersed by insects that feed on poisoned bait without harm and retain the pesticide within their bodies.

Further reading

  • Tasheva, M. (1995). Environmental Health Criteria 175: Anticoagulant rodenticides. World Health Organisation: Geneva.
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