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Extension Toxicology Network

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and University of California at Davis. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.


Publication Date: 9/93


Common names include diphacin (Italy and Turkey), ratindan (USSR), dipazin, diphenadione and diphenacin (2). Trade names include Diphacine, Ditrac, Gold Crest, Kill-Ko, P.C.Q., Promar, Ramik, Rat Killer, Rodent Cake.


All formulations containing 3% or more of diphacinone are classified as Restricted Use Pesticides (RUP) by the EPA. RUPs may be purchased and used only by certified applicators. The signal word required on products containing diphacinone varies, depending on the type of formulation. "Danger" is required for the technical material. "Warning" is required for concentrate formulations and "Caution" is required for bait formulations (3).


Diphacinone is an anti-coagulant rodenticide bait used for control of rats, mice, voles and other rodents. It is available in meal, pellet, wax block, and liquid bait formulations, as well as in tracking powder and concentrate formulations.



Diphacinone is highly toxic to humans and other mammals by inhalation, dermal absorption, and ingestion (4). It causes internal hemorrhaging that can lead to death. It acts by inhibiting enzymes involved in blood clotting (2). Animals given lethal doses exhibited labored breathing, muscular weakness, excitability, fluid in the lungs, and irregular heartbeats. Other signs of poisoning include spitting of blood, bloody urine or stools, internal hemorrhaging, and widespread bruising or bleeding into the joints. When a lethal dose does not cause immediate death, then death tends to be delayed and due to massive hemorrhage (4).

Diphacinone does not irritate the skin and it is not a skin sensitizer (2). It is a mild eye irritant.

The amount of a chemical that is lethal to one-half (50%) of experimental animals fed the material is referred to as its acute oral lethal dose fifty, or LD50. The oral LD50 for technical diphacinone in rats is 0.3 to 7 mg/kg, 3.0 to 7.5 mg/kg in dogs, 14.7 mg/kg in cats, 150 mg/kg in pigs, 50 to 300 mg/kg in mice, and 35 mg/kg in rabbits (2, 3, 4). The dermal LD50 in rats is 200 mg/kg (4), and in rabbits is greater than 3.6 mg/kg. The lethal concentration fifty, or LC50, is that concentration of a chemical in air or water that kills half of the experimental animals exposed to it for a set time period. The 4-hr inhalation LC50 in rats is 2 mg/m3 (4, 6).


EPA does not require data on the chronic health effects of diphacinone because this pesticide is used in a manner which poses only a minimal hazard of chronic human exposure.

Reproductive Effects

Because diphacinone is used in a manner which poses no hazard of chronic exposure to humans, EPA does not require testing for potential effects on reproduction.

Teratogenic Effects

Tests results regarding potential teratogenicity of diphacinone will be submitted to EPA by June of 1993.

Mutagenic Effects

Diphacinone was not mutagenic in the Ames test (2). Mutagenicity data was under review by EPA during October 1992.

Carcinogenic Effects

Because diphacinone is used in a manner which poses only a minimal hazard of chronic exposure to humans, EPA does not require testing for potential carcinogenic effects.

Organ Toxicity

Poisoning by diphacinone may affect the heart and gastrointestinal system (4).

Fate in Humans and Animals

Three to 7.5 hours after radio-labeled diphacinone was given orally to mice, the highest concentrations appeared in the liver and lungs. In another study, rats given oral doses eliminated 70% of the dose in the feces and 10% in the urine within 8 days. A similar pattern of elimination occurred in mice given the same treatment. Levels of diphacinone were highest in the liver and significant in the kidneys and lungs 4 and 8 days after treatment for rats and mice respectively. Diphacinone is not extensively metabolized in rats, with less than 1% of the dose expired as carbon dioxide (2).

The half-life of diphacinone in humans is 15 to 20 days (2).


Effects on Birds

Diphacinone is slightly toxic to birds. The oral LD50 for diphacinone in mallard ducks is 3158 mg/kg (2, 5), and in bobwhite quail is 1630 mg/kg.

Effects on Aquatic Organisms

Diphacinone is slightly to moderately toxic to fish. The 96-hour LC50 for technical diphacinone in channel catfish is 2.1 mg/l, for bluegills is 7.6 mg/l, and for rainbow trout is 2.8 mg/l (1, 5). The 48-hour LC50 in Daphnia, a small freshwater crustacean, is 1.8 mg/l.

Effects on Other Animals (Nontarget species)

No information available.


Breakdown of Chemical in Soil and Groundwater

Diphacinone has a low potential to leach in soil (6).

Breakdown of Chemical in Water

Diphacinone is rapidly decomposed in water by sunlight (2).

Breakdown of Chemical in Vegetation

No information available.


Technical diphacinone is an odorless, pale yellow powder (3). Diphacinone is stable under normal temperatures and pressures. It may burn, but does not ignite readily. Thermal decomposition of diphacinone may release carbon monoxide and carbon dioxide (4, 1).

Exposure Guidelines:

No occupational exposure limits have been established for diphacinone by OSHA, NIOSH or ACGIH (4).

Physical Properties:

CAS #: 82-66-6
Specific gravity: 1.6
H20 solubility: almost insoluble; 0.3 mg/l (2, 4)
Solubility in other solvents: soluble in acetone (29 gm/l), acetic acid and toluene (73 gm/l). slightly soluble in benzene (2, 4)
Melting point: 295-297 degrees F (146-147 degrees C) (4)
Decomposition temperature: Technical material decomposes at 338 degrees C without boiling (5)
Vapor pressure: 13.7 mm Hg at 25 degrees C (technical) (5)
Chemical Class/Use: anticoagulant rodenticide


Bell Laboratories, Inc.
3699 Kinsman Blvd.
Madison, WI 53704

Hacco Inc.
P.O. Box 7190
537 Atlas Ave.
Madison, WI 53707
Telephone: 608-221-6200

Review by Basic Manufacturer - Bell Labs:

Comments solicited: October, 1992.
Comments received: November, 1992.

Review by Basic Manufacturer - Hacco Inc.:

Comments solicited: October, 1992.
Comments received: November, 1992.


  1. Bell Laboratories, Inc. July, 1990. Diphacinone Technical: MSDS. Bell Labs, Madison, WI.
  2. Hayes, W.J. and E.R. Laws (ed.). 1990. Handbook of Pesticide Toxicology, Vol. 3, Classes of Pesticides. Academic Press, Inc., NY.
  3. Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister Publishing Company, Willoughby, OH.
  4. Occupational Health Services, Inc. 1991 (Sept. 16). MSDS for Diphacinone. OHS Inc., Secaucus, NJ.
  5. Worthing, C.R., ed. 1983. The Pesticide Manual: A World Compendium, 7th Ed. British Crop Protection Council, Croydon, England.
  6. US Environmental Protection Agency. 1991 (Feb 25). Pesticide Environmental Fate One Line Summary: Diphacinone. Environmental Fate and Effects Div., US EPA, Washington DC.