Pharmacotherapeutic group: Ectoparasiticides for topical use, fipronil, combinations
ATCvet code: QP53AX65
Pharmacodynamic properties
Fipronil is an insecticide and acaricide belonging to the phenylpyrazole family. Fipronil and its metabolite fipronil sulfone act at ligand-gated chloride channels, in particular those gated by the neurotransmitter gamma-aminobutyric acid (GABA) as well as desensitising (D) and non-desensitising (N) channels gated by glutamate (Glu, unique invertebrate ligand-gated chloride channels), thereby blocking pre- and post-synaptic transfer of chloride ions across cell membranes. This results in uncontrolled activity of the central nervous system and death of insects or acarid.
Pyriproxyfen is an insect growth regulator (IGR) of the class of compounds known as juvenile hormone analogues. Pyriproxyfen sterilises adult fleas and inhibits the development of immature stages. The molecule prevents, by contact, the emergence of adult insects by blocking the development of eggs (ovicidal effect), larvae and pupae (larvicidal effect), which are subsequently eliminated. Following contact and/or ingestion by adult fleas, the molecule also acts by sterilising eggs during their maturation and before being laid. The molecule prevents contamination of the environment of treated animals with the immature stages of fleas
Combination of fipronil and pyriproxyfen provides an insecticidal and acaricidal activity against fleas (Ctenocephalides felis), ticks (Rhipicephalus sanguineus, Dermacentor reticulatus, Ixodes ricinus) in addition to preventing flea eggs developing into adult fleas.
Pharmacokinetic particulars
Following topical application of the product to dogs, under the normal conditions of use, fipronil and pyriproxyfen are well distributed across the haircoat of the dog by 24 hours.
The major metabolite of Fipronil is the sulfone derivative, which also possesses insecticidal and acaricidal properties.
The concentrations of fipronil, fipronil sulfone and pyriproxyfen in the haircoat decrease over time but are still detectable for at least 84 days after application.
After administration of the product, the plasmatic peak concentration is reached between 3 to 7 days for fipronil and between 7 to 14 days for fipronil sulfone. The plasmatic peak concentration of pyriproxyfen is reached between 1 to 3 days after administration.
The plasmatic concentrations of fipronil and pyriproxyfen decrease over time and the concentrations are quantifiable up to 50 days after application.