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in 1996. EXTOXNET no longer updates this information, but it may be useful
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E X T O X N E T
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Common names include diphacin (Italy and Turkey), ratindan (in
the former U.S.S.R.), dipazin, diphenadione, and diphenacin.
Trade names include Diphacine, Ditrac, Gold Crest, Kill-Ko,
P.C.Q., Promar, Ramik, Rat Killer, Rodent Cake, and Tomcat.
Diphacinone is an highly toxic compound in EPA Toxicity Class I.
All formulations of diphacinone are Restricted Use Pesticides
(RUPs). 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
applies to the technical material, WARNING to concentrate
formulations, and CAUTION to bait formulations.
Chemical Class: Not
Diphacinone is a 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. It may also be used as a
anticonvulsant drug under the name of diphenadione. It has also
been used successfully in controlling vampire bats, a vector for
Formulation: It is
available in meal, pellet, wax block, and liquid bait
formulations, as well as in tracking powder and concentrate
- Acute toxicity: Diphacinone is highly
toxic by ingestion, with oral LD50 values of 0.3 to 7
mg/kg in rats, 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 [1,172]. It is highly toxic by skin
exposure, with reported dermal LD50 values of less than
200 mg/kg in rats, 340 mg/kg in mice, and greater than
3.6 mg/kg in rabbits [1,172]. It is not reported to be a
skin or eye irritant in rabbits, nor a skin sensitizer in
guinea pigs [1,172]. The 4-hour inhalation LC50 of
diphacinone in rats of less than 2 mg/L also indicates
high toxicity [1,173]. Diphacinone works by inhibition of
liver-synthesized coagulation proteins, leading to
internal hemorrhaging . If the dose is sufficient,
this may result in death . Effects exhibited in test
animals during acute LD50 testing included labored
breathing, muscular weakness, excitability, congested
blood flow to the lungs, and irregular heartbeats. Other
signs of poisoning include spitting of blood, bloody
urine or stools, and widespread bruising or bleeding into
the joints . Use in humans as an anticoagulant drug
has been apparently discontinued, possibly due to its
structural similarity to another compound (phenindone).
Phenindone was noted to pose risks of hepatitis with
jaundice, damage to kidneys, severe skin irritation, and
and massive tissue swelling . The use history of
diphacinone indicates that it produced no adverse health
effects except occasional nausea and some hemorrhagic
effects that persisted for 6 to 10 days . In other
case reports, the anticoagulant effects are reported to
persist for several weeks to months .
- Chronic toxicity: No permanent or
life-threatening effects occurred in humans on
recommended dose regimes of an initial 20 mg dose (ca.
0.29 mg/kg in a 70 kg human), followed by successive 2 to
4 mg daily doses (ca. 0.03 to 0.06 mg/kg/day in a 70 kg
person) for several days to weeks . All test animals
exposed at dietary levels of 0.1 and 0.2 mg/kg/day in a
21-day study showed fatal massive internal hemorrhaging,
although at doses of 0.05 mg/kg/day, they were unaffected
. In a 90-day study in which rats were given dietary
doses of 0.002 to 0.025 mg/kg/day, single rats in each of
the 0.003 and 0.013 mg/kg/day dose groups died from
internal hemorrhage, but the others remained unaffected
by treatment . The effects due to chronic exposure
are similar to those which may be expected from acute
exposure, but animal studies and human use experience
suggest that there is a level of chronic exposure at
which no adverse health effects may occur. The available
studies also suggest that some individuals in any
population may be much more succeptible to effects than
others. These individuals may include those with poor
nutritional status and/or Vitamin K deficiency, liver or
kidney disorders, or infectious diseases .
- Reproductive effects: No data are
currently available .
- Teratogenic effects: No data are
currently available .
- Mutagenic effects: Diphacinone was not
mutagenic in the Ames test [1,172]. No other data
regarding mutagenic effects are currently available
- Carcinogenic effects: No data are
- Organ toxicity: The principal target of
diphacinone is the blood (specifically the clotting
factors), but effects on the liver, kidneys, heart, and
musculature have been seen, probably as secondary
- Fate in humans and animals: Rats
eliminated 70% of the administered oral dose via the
feces and 10% in the urine within 8 days . A similar
pattern of elimination occurred in mice . Animal
studies indicate that little metabolism takes place, and
that diphacinone which is not eliminated may concentrate
to varying degrees in the liver, kidneys, and lungs
[8,172]. The half-life of diphacinone in humans is 15 to
20 days . It was determined that cattle dosed with the
compound as an anti-bat measure were safe to use for
dairy and/or meat production .
- Effects on birds: Diphacinone is
slightly toxic to birds. The oral LD50 for diphacinone in
mallard ducks is 3158 mg/kg [1,8], and in bobwhite quail
is 1630 mg/kg .
- Effects on aquatic organisms:
Diphacinone is moderately toxic to fish species. The
96-hour LC50 for technical diphacinone in channel catfish
is 2.1 mg/L, in bluegills is 7.6 mg/L, and in rainbow
trout is 2.8 mg/L [1,174]. The 48-hour LC50 in Daphnia, a
small freshwater crustacean, is 1.8 mg/L .
- Effects on other organisms: Studies with
cattle indicate a high degree of tolerance for the
compound, hence its use against vampire bats preying on
cattle in Latin America .
- Breakdown in soil and groundwater:
Diphacinone has a low potential to leach in soil .
- Breakdown in water: Diphacinone is
rapidly decomposed in water by sunlight .
- Breakdown in vegetation: No data are
- Appearance: Technical diphacinone is an
odorless, pale yellow powder .
- Chemical Name:
- CAS Number: 82-66-6
- Molecular Weight: 340.38
- Water Solubility: 0.3 mg/L; almost
- Solubility in Other Solvents: v.s. in
acetone, acetic acid, toluene, xylene, and chloroform 
- Melting Point: 145-147 C 
- Vapor Pressure: 13.7 nPa @ 25 C
- Partition Coefficient: Not Available
- Adsorption Coefficient: Not Available
- ADI: Not Available
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
P.O. Box 7190
537 Atlas Ave.
Madison, WI 53707
- Phone: 608-221-6200
- Emergency: 800-642-4699
References for the information in this PIP can be found in
Reference List Number 10
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide