Brodifacoum (Talon, Havoc) - Chemical Profile 1/85
CHEMICAL name: 2-[3-(4'-bromo[1-1'-biphenyl]-4-yl)-1,2,3,4-tetra-
TRADE name(S): Klerat, Ratak Plus, Talon, Volid, Havoc (56)
FORMULATION(S): Ready-to-use grain-base bait in pellets, mini
pellets, and waterproof Weather-Blok bait
containing 0.005% brodifacoum (loose or
bait-packs). Talon for professional operators;
Havoc for general usage (56).
TYPE: Rodenticide (anticoagulant)
BASIC PRODUCER(S): Syngenta
410 Swing Rd.
Greensboro, NC 27409
STATUS: General use
PRINCIPAL USES: A rodenticide of exceptional activity against a
variety of pest rodents. Currently registered in U.S. for control of
Norway rats, roof rats, and house mice in public, industrial and
commercial buildings, residential, as well as for urban outdoor use by
professional pest control personnel and commercial rodent control in
and around farm buildings (56).
Effective against rodents which are resistant to conventional
anticoagulants. Only a single feeding necessary for rodent death
to occur (56).
Its potency is such tht, unlike other anticoagulants, a rodent may
absorb a lethal dose by taking a 50 mg/kg bait as part of its feed
intake on only one occasion (62).
It has an acute as well as chronic effect on rodents. Slow acting
with the rodents dying in 3-7 days (8c).
BIOLOGICAL ACTIVITY: Havoc is the most active anticoagulant on mice and
rats. Yet, research has shown Havoc to be less active on nontarget
animals than some multiple feeding anticoagulants. Listed below is a
comparison of acute LD50 values for various anticoagulants on these
Acute Oral LD50 (mg/kg)
Norway Rat House Mouse
Brodifacoum (Havoc) 0.27 0.40
Warfarin 58.0 347.0
Diphacinone 3.0 141.0
Bromadiolone 1.13 1.75
Havoc in the finished bait is effective in extremely small amounts on
mice and rats. However, there is sufficient specificity to create a
margin of safety to nontarget species. Listed below is a comparison of
lethal doses for various finished baits indicating their toxicity to
rodents as well as to nontarget species.
Amounts of Bait Necessary (in grams)
To give an LD50
Mice 0.025 kg Rats, 0.25 kg
body weight body weight
Havoc 0.2 g (0.005%) 1.4 g (0.005%)
Warfarin 37.0 g (0.025%) 58.0 g (0.025%)
Diphacinone 70.0 g (0.005%) 11.5 g (0.005%)
Zinc Phosphide .45 g (2.5%)
Amounts of Bait Necessary (in grams)
To Give an LD50
Cats 2 kg Dogs 5 kg
body wt body wt
Havoc 1000 g (0.005%) 355-1000 g (0.005%)
Warfarin 48-320 g (0.025%) 400-500 g (0.025%)
Diphacinone 588 g (0.005%) 88 g (0.005%)
Zinc Phosphide 1.6 g (2.5%) 4-8 g (2.5%)
Laboratory Tests - Havoc bait at 0.005% (50 ppm) has been shown to be
highly efficacious against commensal rodent species, as indicated in
the table below.
Feeding Tests with 0.005% Havoc Bait
on Various Rodent Species
Feeding No. Days % No.
Species Distribution Choice of Feeding Kill Tested
Rattus Worldwide None 1 100 25
norvegicus Free 1 90 20
(Norway Rat) Free 3 95 100
Rattus Johnston None 1 100 12
norvegicus Cy., NC Free 3 100 12
Rattus Worldwide None 1 90 20
rattus Free 2 100 20
(Roof rat) Free 3 100 20
Mus Worldwide None 1 95 20
Efficacy of Havoc to Cross-Resistant Wild
Norway Rats (U.S. Data Jackson, Unpublished)
Test Criteria Warfarin Pival Havoc
Concentration (ppm) 50 50 50
Mean Body Weight (g) 228 289 285
Mean Dose Ingested (mg/kg) 25.6 25.9 16.4
Mean Daily Consumption (g) 18.2 24.6 15.6
Mortality 0/7 0/7 7/7
In similar testing with confirmed warfarin-resistant house mice Havoc
killed 100% of the test population. This demonstrates the
effectiveness of Havoc against resistant house mice.
Efficacy of Havoc to Warfarin Resistant
Wild House Mice (U.S. Data Frantz, Unpublished)
Mean body weight 19.4 g
Mean ingested dose 12.9 mg/kg
Rodenticides may be compared based on resistance factors. These
factors are a measure of a compound's potential activity against
resistant rodents. Below is a comparison of resistance factors for
several anticoagulants. The closer the number is to 1, the more
potentially effective the compound is against resistant rodents.
Rattus Norvegicus (Norway rat) Resistance Factors
of Anticoagulants (from Hadler and Shadbolt, 1975)
Anticoagulant Resistance Factor
FIELD RESISTANCE EFFICACY
A field study was conducted at a site where a high level of
resistance has been noted. Tracking boards and consumption of bait
were recorded prior to and after baiting with Havoc. The site was a
poultry farm with four buildings, each having a large population of
Norway rats. Havoc was very effective in controlling these rats with a
documented high level of resistance to Warfarin.
Results From Site Having Confirmed Resistance to
Warfarin (from Apperson, Sanders and Kaukeinen)
Consumption % Inactive
(g/station day) Tracking Boards
Building % %
# Pre Post Reduction Pre Post Reduction
1 10.2 1.3 87.5 0.7 86.3 99.2
2 49.3 1.3 97.4 0.3 53.6 99.5
3 15.1 0.8 94.9 11.8 77.0 84.7
4 77.5 1.9 88.9 4.1 91.2 95.5
The grain-based formulations which are available surpass EPA
acceptance requirements (33%) for conventional anticoagulants.
Acceptance levels of over 60% have been documented for groups of wild
Norway rats and house mice.
SIX HOUR NO-CHOICE FEEDING
In a laboratory experiment, 4 wild Norway rats were allowed to
feed upon Havoc bait for 6 hours, in a no-choice situation.
Twenty-three of the 24 rats died (96%) with an average day of death of
just over 6 days. In similar testing 2 groups of Norway rats were
allowed to feed on Havoc bait for 24 hours. All of the animals in both
groups died with an average time of death near 6 days (20e).
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C31 H23 Br O3 (62)
MOLECULAR WEIGHT: 523.4 (62)
PHYSICAL STATE: Off-white to fawn powder (62)
MELTING POINT: 228-232 C (62)
VAPOR PRESSURE: <133 uPa at 25 C (62)
SOLUBILITY: <10 mg/l water at pH 7 at 20 C; it is a weak acid
which does not form water-soluble salts (62).
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: NA
NIOSH RECOMMENDED LIMIT: NA
ACGIH RECOMMENDED LIMIT: NA
A. ACUTE TOXICITY
DERMAL: LD50 = 50 mg tech./kg, 200 mg a.i. (as dust)/kg for
6-hr. exposure (rat) (62).
LD50 = low dermal toxicity, practically nonirritating
to skin (rabbit, finished bait - 50 ppm brodifacoum)
ORAL: LD50 = 0.27 mg a.i./kg (male rat); 0.3 mg/kg (male
rabbit); 0.4 mg/kg (male mouse); 2.8 mg/kg (female
guinea pig); c. 25 mg/kg (cat); 0.25-1.0 mg/kg (dog);
4.5 mg/kg (chicken) (62).
LD50 = 5,600 mg/kg (rat, finished bait containing 50
ppm (0.005%) brodifacoum) (20e).
INHALATION: No toxicological response evoked in tests (rat,
finished bait - 50 ppm brodifacoum) (20e).
B. SUBACUTE AND CHRONIC TOXICITY:
In 42-day feeding trials rats receiving 0.1 mg/kg diet suffered no
IV. ENVIRONMENTAL CONSIDERATIONS
Acute oral LD50 = 2.0 mg/kg for mallard duck (62).
LC50 (96 hr) is: for bluegill 0.165 mg/l; for rainbow trout 0.051
Effective at such low rates that the risk of secondary poisoning to
other animals is minimal. Relatively non-toxic to bird species (8c).
This product can be toxic to wildlife and can pose a secondary
hazard to birds of prey and mammals. Extensive research with predatory
animals, such as barn owls, has shown that such predators are not
normally at risk when Havoc is used according to label directions
(Kaukeinen 1982) (20e).
V. EMERGENCY AND FIRST AID PROCEDURES
The chemical information provided below has been condensed from
original source documents, primarily from "Recognition and Management
of Pesticide Poisonings", 3rd ed. by Donald P. Morgan, which have been
footnoted. This information has been provided in this form for your
convenience and general guidance only. In specific cases, further
consultation and reference may be required and is recommended. This
information is not intended as a substitute for a more exhaustive
review of the literature nor for the judgement of a physician or other
If poisoning is suspected, do not wait for symptoms to develop.
Contact a physician, the nearest hospital, or the nearest Poison
FREQUENT SYMPTOMS AND SIGNS OF POISONING:
Coumarins, indandiones, and other anticoagulants: In most cases
of ingestion of anticoagulants, victims have remained asymptomatic, due
to the small dosage taken. Even in cases involving ingestion of
substantial amounts of anticoagulant compound (more often medication
than rodenticide), hypoprothrombinemia has occurred without symptoms of
poisoning. Hemorrhage appears only when extraordinary amounts have
been absorbed. In reported cases, the anticoagulants were either taken
deliberately, were absorbed over long periods out of neglect of
elementary hygienic standards, or were ingested by starving indigents
who used quantities of rodent bait as food.
Victims of large doses exhibit HEMATURIA, NOSEBLEED, HEMATOMATA,
BLEEDING GUMS, and MELENA, ABDOMINAL PAIN and BACK PAIN probably
reflect hemorrhage in the abdominal and retroperitoneal tissues.
WEAKNESS occurs as a result of ANEMIA. RENAL COLIC often complicates
severe hematuria. Nasal and gastrointestinal hemorrhages have
occasionally caused death from exsanguination (25).
NOTES TO PHYSICIAN:
Coumarins, indandiones, and other anticoagulants
1. If only a few grains of anticoagulant bait have been ingested by
an adult or child having no antecedent liver or blood clotting
disease, treatment is probably unnecessary.
A. If there is uncertainty about the amount of bait ingested or
the general health of the patient, PHYTONADIONE (vitamin K1,
Mephyton) given orally protects against the anticoagulant
effect of these rodenticides. For adults, give 15-25 mg; for
children under 12, give 5-10 mg. Alternatively, a colloidal
solution of phytonadione, Aquamephyton, may be given
intramuscularly. For adults, give 5-10 mg; for children under
12, give 1-5 mg.
CAUTION: PHYTONADIONE, specifically, is required. Neither
vitamin K3 (menadione, Hykinone) nor vitamin K4
(menadiol) is an antidote for these anticoagulants.
B. Whatever the dosage, insure that patients (especially
children) will be CAREFULLY OBSERVED for 4-5 days after
ingestion. The indandiones and the more recently introduced
anticoagulants have toxic effects apart from anticoagulation
that are not yet well defined.
2. If LARGE AMOUNTS of anticoagulant were ingested in the preceding
2-3 hours, INDUCE VOMITING with SYRUP OF IPECAC, followed by 1-2
glasses of water. For adults, give 30 ml; for children under 12,
15 ml. Following emesis, give 30-50 gm ACTIVATED CHARCOAL in 4-6
ounces of water to limit absorption of anticoagulant remaining in
3. If anticoagulant has been ingested any time in the preceding 15
days, determination of PROTHROMBIN TIME provides a basis for
judging the severity of poisoning.
A. If the prothrombin time is lengthened, give Aquamephyton,
intramuscularly: adult dose, 5-10 mg; child's dose: 1-5 mg.
Decide dose according to the degree of prothrombin time
lengthening and, in children, the age and weight of the child.
B. Repeat prothrombin time in 24 hours. If it has not decreased
from the original value, repeat Aquamephyton dosage.
4. If victim shows SYMPTOMS or SIGNS of ANTICOAGULANT POISONING
(bleeding) in addition to hypoprothrombinemia, administer
Aquamephyton intramuscularly, up to 25 mg in the adult, and up to
0.6 mg/kg in children under 12 years. Phytonadione administration
may be repeated in 24 hours if bleeding continues.
A. In cases of SEVERE BLEEDING, it may be necessary to give
Aquamephyton intravenously. This is especially true if the
bleeding tendency is so severe that intramuscular injection is
likely to cause hematoma formation. Dosage is up to 25 mg in
the adult, up to 0.6 mg/kg in children under 12 years. Repeat
this dose in 24 hours if bleeding continues. Inject at rates
not exceeding 5% of the total dose per minute. INTRAVENOUS
INFUSION of the Aquamephyton DILUTED IN SALINE OR GLUCOSE
SOLUTION is recommended. Bleeding is usually controlled in
CAUTION: Adverse reactions, some fatal, have occurred from
INTRAVENOUS phytonadione injections, even when
recommended dosage limits and injection rates were
observed. For this reason, the INTRAVENOUS route
should be used ONLY IN cases of SEVERE POISONING.
Flushing, dizziness, hypotension, dyspnea, and
cyanosis have characterized adverse reactions.
B. Antidotal therapy IN cases of SEVERE BLEEDING should be
supplemented with TRANSFUSIONS of FRESH BLOOD or FRESH FROZEN
PLASMA. Use of fresh blood or plasma represents the most
rapidly effective method of stopping hemorrhage due to these
C. Determine PROTHROMBIN TIMES (and hemoglobin concentrations, if
appropriate) every 6-12 hours to assess effectiveness of
D. When normal blood coagulation is restored, it may be advisable
to drain large hematomata.
E. Ferrous sulfate therapy may be appropriate in the recuperative
period to rebuild lost erythrocyte mass (25).
VI. FIRE AND EXPLOSION INFORMATION
To be developed.
To be developed.
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Keep away from children, domestic animals and
wildlife. Wash hands after handling bait. Avoid all contact by
mouth. Do not allow to contaminate food, feed or water supplies.
After treatment, remove and bury uneaten bait and rodent bodies. Keep
container closed to maintain freshness of bait. Do not reuse empty
Finished bait is stable 2 years at ambient temperatures in sealed
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
X. LITERATURE CITED
8c. Thomson, W.T. 1980. Agricultural chemicals - book III:
fumigants, growth regulators, repellents, and rodenticides.
1981 revised ed. Thomson Publications, Fresno, CA. 182 pp.
20e. ICI Americas, Inc., Agricultural Chemicals Division. 1983.
Technical information: Havoc rodenticide. Wilmington,
25. Morgan, D.P. 1982. Recognition and management of pesticide
poisonings, 3rd ed. U.S. Environmental Protection Agency,
Washington, DC. 120 pp.
56. Farm Chemicals Handbook, 70th ed. 1984. R. T. Meister, G. L.
Berg, C. Sine, S. Meister, and J. Poplyk, eds. Meister
Publishing Co., Willoughby, OH.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.