Page 566 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

VetBooks.ir Chapter 42

Fipronil

Ramesh C. Gupta and Arturo Anado´n

INTRODUCTION different mechanism compared to other conventional
insecticides (Narahashi, 2000; Narahashi et al., 2007,
Fipronil is a member of a new class of insecticides called
2010). It is poorly soluble in water, delivered in very
phenylpyrazoles. Chemically, it is a (5-amino-1-[2,6-
small amounts and does not leach into groundwater. In
dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sul-
1996, it was registered as a pesticide in the United States
finyl]-1H-pyrazole). The chemical structure of fipronil is
(Bobe et al., 1998). It can be formulated as roach or ant
shown in Fig. 42.1. Fipronil is an active ingredient of
baits, flea and tick sprays for pets, and in granular turf
one of the popular ectoparasiticide products, Frontline. products to control mole crickets (Kidd and James, 1991;
Fipronil is also present in other ectoparasiticide products,
EPA, 1996). In addition, fipronil is used for soil treatment
such as Certifect and Parastar Plus. There are currently
and to protect crops from insects. Unlike many modern
two forms of Frontline preparation commercially avail-
pesticides, fipronil and its derivatives are moderately
able (a spray and a spot-on topical application) for dogs
persistent in the environment (EPA, 1996; Gunasekara
and cats. The product is meant to kill fleas and all stages
et al., 2007). It is currently used worldwide and has good
of brown dog ticks, American dog ticks, lone star ticks,
adulticide activity against fleas and ticks. It has signifi-
which may carry Lyme disease, and mites (Cutler, 1998;
cant residual activity and for small animal use is available
Hutchinson et al., 1998; Anonymous, 2000). Fipronil
as a spray or spot-on product. Sunlight, immersion in
is used in combination with methoprene (9.8% fipronil/
water and bathing do not significantly impact the perfor-
11.8% methoprene for cats; 9.8% fipronil/8.8% metho-
mance of this compound and it kills adult fleas within
prene for dogs) for additional control of immature flea
24 h (Kunkle, 1997). Fipronil has also been used to treat
stages. Fipronil is also formulated as insect bait for
some mite infections.
roaches, ants and termites; as sprays for pets; and as a
Most fipronil poisoning cases occur in dogs and cats
granular turf product to control mole crickets. Presently,
due to accidental ingestion or licking the product
fipronil is widely used in agriculture for soil treatment
Frontline, Certifect, or Parastar Plus. Frontline preparation
and seed coating.
for dogs contains 132 mg fipronil in a 1.34 mL tube that
Currently, fipronil-based products with various trade
is meant for topical application. In humans, poisoning is
names (Chipco, Choice, ICON 6.2FS, and Over n’ Out,
mainly due to accident or suicidal attempt. In a published
TeckPac, Frontline) have gained popularity worldwide for
report, the Paris Poison Center, France, recorded 81
pest management, including residential insect control, rice
human cases of fipronil exposure from 1994 to 1999. Out
and cotton production, and turf-grass management. The
of these 81 cases, 57 involved veterinary ectoparasiticides
EPA has determined fipronil to be safe for use on dogs and
and seven used domestic insecticide preparations (Gasmi
cats, with no harm to humans who handle these animals. et al., 2001).
Poisoning cases from accidental use or misuse of fipronil
may occur in animals. This chapter describes the toxicity of
fipronil in various species of animals, birds and fish. PHARMACOKINETICS/TOXICOKINETICS
Fipronil in Frontline (132 mg in 1.34 mL liquid), Certifect
(9.8% of 4.28 mL), or Parastar Plus (9.8% of 2.68 mL)
BACKGROUND
is placed between the dog’s shoulder blades at the nape
Fipronil was first discovered by Rhone-Poulenc Agro in of the neck. After application, fipronil spreads and
1987 and is used worldwide in agriculture. It represents sequesters in the lipids of the skin and hair follicles, and
the second generation of insecticides that acts through a continues to be released onto the skin and coat, resulting
Veterinary Toxicology. DOI: http://dx.doi.org/10.1016/B978-0-12-811410-0.00042-8
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