Oral pharmacokinetic profile of fipronil and efficacy against flea and tick in dogs.

Abstract

Fipronil (FIP) is an ectoparasiticide of the phenylpyrazole class, used in veterinary medicine in topical form. Supported by evidence of uncontrolled human exposure to FIP and environmental damage caused by commercially available formulations, its use by oral administration has become promising. The effectiveness of FIP against the flea Ctenocephalides felis felis and the tick Rhipicephalus sanguineus and its pharmacokinetics and main active metabolite, fipronil sulfone (SULF) were evaluated after single oral administration of tablets in three different doses (2, 4, and 6mg/kg) in dogs. Through the plasma concentration curves, it was possible to observe that the FIP showed rapid absorption and metabolization and slow elimination. The values of Cmax (β=0.7653) and AUC0- t (β=0.3209) did not increase proportionally with increasing dose. At 48h after treatment, doses of 4mg/kg (AUC0- t =442.39±137.35µg/ml*h) and 6mg/kg (AUC0- t =421.32±102.84µg/ml*h) provided 100% and 99% efficacy against fleas, and 95% and 98% against ticks, respectively. The estimated EC90 of FIP +SULF was 1.30µg/ml against C. felis felis and 2.16µg/ml against R. sanguineus. The correlation between the FIP pharmacokinetic and efficacy data demonstrated its potential for oral administration in the form of tablets for the control of ectoparasites in dogs, as a safer alternative for animals, humans, and the environment, aligned with the One Health concept.