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Title: Brodifacoum  
Author: World Heritage Encyclopedia
Language: English
Subject: Rodenticides, Phenylsilatrane, 1080 usage in New Zealand, Index of pesticide articles, SS Winfield Scott
Publisher: World Heritage Encyclopedia


IUPAC name
Other names
ChemSpider  YesY
Jmol-3D images Image
RTECS number GN4934750
Molar mass 523.43 g·mol−1
Melting point 228 to 230 °C (442 to 446 °F; 501 to 503 K)
Lethal dose or concentration (LD, LC):
LD50 (Median dose)
270 μg/kg (rat, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 YesY  (: YesY/N?)

Brodifacoum is a highly lethal 4-hydroxycoumarin vitamin K antagonist anticoagulant poison. 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 pests such as possum.[2]

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.

Chemical synthesis

Brodifacoum is a derivative of the 4-hydroxy-coumarin group. Compound 1 is the starting ester needed to synthesize brodifacoum. To obtain this starting compound a simple Wittig condensation of ethyl chloroacetate with 4’-bromobiphenylcarboxaldehyde was accomplished. Compound 1 was transformed into 2 by consecutive hydrolysis, halogenation to form an acid chloride, and then reacted with the required lithium anion. This was done using KOH and EtOH for hydrolysis, and then adding SOCl2 for chlorination to form the acid chloride which reacted with the addition of lithium anion. Compound 2 was then transformed using Friedel-Crafts type cyclization would be utilized to obtain the two ring system portion of compound 4, but there were issues of low yield. Instead trifluoromethanesulfonic acid in dry benzene catalyzed the cyclization in good yield. The ketone was then reduced with sodium borohydride yielding a benzyl alcohol. Condensation with 4-hydroxycoumarin under HCl yielded compound 5, brodifacoum.[3]

Stereospecific formation of Brodifacoum using an asymmetric organocopper compound.


Brodifacoum is a 4-hydroxycoumarin anticoagulant, with a similar mode of action to its historical predecessors dicoumarol and warfarin. However, due to very high potency and long duration of action (elimination half-life of 20 – 130 days), it is characterised as a "second generation" or "superwarfarin" anticoagulant.[4]

Brodifacoum inhibits the enzyme vitamin K epoxide reductase. 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 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.

Brodifacoum is highly lethal to mammals and birds, and extremely lethal to fish. It is a highly cumulative poison, due to its high lipophilicity and extremely slow elimination.

Following are acute LD50 values for a variety of animals:
* rats (oral) 0.27 mg/kg b.w.[5]
* mice (oral) 0.40 mg/kg b.w.[5]
* rabbits (oral) 0.30 mg/kg b.w.[5]
* guinea-pigs (oral) 0.28 mg/kg b.w.[5]
* squirrels (oral) 0.13 mg/kg b.w.[6]
* cats (oral)[7] 0.25 mg/kg[8][5] — 25 mg/kg [9][10][11][12][5][13]
* dogs (oral) 0.25 — 3.6 mg/kg b.w.[5][8][9][10][11][12]
* birds LD50 values for various birds varies from about 1 mg/kg b.w. — 20 mg/kg b.w.[4]
* fish — LC50 for fish:
** trout (96 hours exposure) 0.04 ppm[14]

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.[4] 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

DOC Notice to hikers of poison baits in New Zealand.
Baitbox from Finland containing brodifacoum

Brodifacoum is marketed under a large variety of trade names, including Ratshot Red,Vertox, Biosnap, d-CON, Finale, Fologorat, Havoc, Jaguar, Klerat, Matikus, Mouser, Pestoff, Ratak+, Rodend, Rodenthor, Ratsak, Talon, Volak, Rakan, Volid, and Rataquill Colombia.

Treatment for humans

The primary antidote to brodifacoum poisoning is immediate administration of vitamin K1 (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 excessive bleeding ensues. 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.[15]

If unabsorbed poison is still in the digestive system, gastric lavage followed by administration of activated charcoal may be required.

Further treatments to be considered include infusion of blood or plasma to counteract hypovolemic shock, and in severe cases, infusion of blood clotting factor concentrate.

Poisoning case reports

There have been case reports of brodifacoum intoxication in the human 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.[16]

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.[17]

In 2015, 19 inmates in New York City's Rikers Island jail claimed that they had been poisoned with the chemical. The inmates had noticed "what appeared to be blue and green pellets in the meatloaf" they were eating on March 3, and felt ill afterwards. A sample was analyzed and tested positive for brodifacoum; the NYC Department of Corrections stated it was investigating the incident.[18][19]

A 20-year-old female college student presented with abdominal pain and blood in urine. She was tested for warfarin, a common anticoagulant also used in some rodenticides, which returned a negative result. Vitamin K and fresh plasma was administered to treat symptoms. 3 weeks later she returned with bleeding into her calf, and was subsequently tested for superwarfarin chemicals. The test showed that Brodifacoum was in her bloodstream. She later admitted to consuming seven packets of rodenticide.[20]

A 48-year-old businessman was admitted with a severe nosebleed as well as abnormal coagulation parameters. Standard treatment of Vitamin K and fresh plasma was administered to stem the nosebleed. Two weeks later he presented again with bleeding into the calf. Continual doses of Vitamin K were necessary to counteract the Brodifacoum. He denied taking any of the Brodifacoum found in his home contained within packages of Contrac.[20]


  1. ^ Merck Index, 11th Edition, 1368
  2. ^ Eason, C.T. and Wickstrom, M. Vertebrate pesticide toxicology manual, New Zealand Department of Conservation
  3. ^
  4. ^ a b c
  5. ^ a b c d e f g
  6. ^
  7. ^ Published LD50 values of brodifacoum for cats vary widely, from 25 mg kg-1 (Rammell et al., 1984;Godfrey, 1985) to 0.25 mg kg-1(Haydock and Eason, 1997)
  8. ^ a b Brodifacoum at
  9. ^ a b KAUKEINEN, D.E. 1979. Experimental rodenticide (Talon) passes lab tests; moving to field trials in pest control industry. Pest Control 46(1):19-21.
  10. ^ a b Brodifacoum (Talon, Havoc) - Chemical Profile 1/85
  11. ^ a b MSDS Data Sheet for TALON RAT AND MOUSE KILLER
  12. ^ a b [Http:// The Veterinarian’s Guide to accidental rodenticideingestion by dogs & cats]
  13. ^ Brodifacoum residues in target and non-target species followin an aerial poisoning operation on Motuihe Island, Hauraki Gulf, NEW ZEALAND Pdf
  14. ^
  15. ^
  16. ^
  17. ^
  18. ^
  19. ^ Sydney Lupkin, "22 Rikers Island Prisoners Sickened By Rat Poison in Meatloaf, Lawyer Says, Daily News April 29, 2015
  20. ^ a b

Further reading

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