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Pharmacological particulars
Pharmacotherapeutic Group: Antiparasitic product, insecticides and repellent. Other ectoparasiticides for topical use, fipronil
ATC Vet Code: QP53AX15
Pharmacodynamic properties
Fipronil is an insecticide/acaricide in the phenylpyrazole family. It acts by inhibiting the GABA complex, binding to the chloride channel and thereby blocking pre- and post-synaptic transfer of chloride ions across the cell membrane. This results in uncontrolled activity of the central nervous system and death in insects and acarids.
Fipronil exhibits insecticidal activity against fleas (Ctenocephalides felis), and acaricidal activity against ticks (Rhipicephalus sanguineus, Dermacentor reticulatus, Ixodes ricinus) in the dog.
Newly arriving fleas are killed within 24 hours of landing on the animal. Ticks if already present at the time of application of the product, may not always be killed in the first 48 hours, however will be killed within 9 days post treatment.
The product is effective against flea infestation (Ctenocephalides felis) for approximately 8 weeks and against tick infestations for up to 4 weeks (see indications for use), depending on the tick species and the level of challenge.
Pharmacokinetic properties
After a local application of fipronil to the dog, it is slightly absorbed through the skin. Low levels of fipronil may be detected in the plasma, with a very high variability between dogs. After application, there is a good distribution of the chemical on the hair, presenting a good gradient of concentration between the application zone and the peripheral area.
Fipronil is mainly metabolised to its sulfone derivative (RM1602), which also possesses insecticidal and acaricidal properties.
The concentrations of fipronil on the hair decrease with time.