title: Injectable fipronil for cattle: Plasma disposition and efficacy against Rhipicephalus microplus.
abstract: Fipronil is a phenylpyrazole class insecticide. It is widely used as an insecticide in agriculture and in the control of ectoparasites in veterinary medicine. The application of fipronil in an injectable form (subcutaneously) becomes an innovation, since there is no commercially available preparation containing fipronil herein. The present study aimed at fipronil usage, applied subcutaneously in cattle, to control Rhipicephalus microplus. The assessing criteria used in the research have been the construction of the plasma concentration curve and efficacy studies. A method using High Performance Liquid Chromatograph with ultraviolet detection was developed for determination of fipronil in bovine plasma samples, providing a fast and simple process with good reproducibility and low limit of quantification. The validation of the analytical method showed linearity, selectivity, precision, accuracy, sensitivity and stability, thus proving it as suitable for routine analysis. This method showed to be an important investigative tool in the analysis of fipronil plasma concentration in cattle. Fipronil administered via subcutaneous in bovine reached the systemic circulation (Cmax=378.06±137.44 ng/mL), was quickly absorbed (t(max)=10±0.87 h), and its elimination occurred slowly (t(1/2)=12 days), while maintaining quantifiable blood plasma levels (23.79±12.16 ng/mL) for up to 21 days after the treatment with a 1 mg/kg dosage. The in vivo efficacy tests proved that fipronil applied subcutaneously in a single dose of 1 mg/kg in cattle exhibited a mean efficacy of 82.41% against R. microplus. The potential of subcutaneous injection as an alternative treatment route in cattle encourage the development of an injectable formulation of fipronil.
authors.affiliation: Chemical Department, Federal Rural University of Rio de Janeiro, BR 465, km 7, 23897-000 Seropédica, RJ, Brazil. Electronic address: yaracid@yahoo.com.br.
authors.forename: Yara P
authors.initials: YP
authors.lastname: Cid
authors.affiliation: Animal Parasitology Department, Federal Rural University of Rio de Janeiro, BR 465, km 7, 23897-000 Seropédica, RJ, Brazil.
authors.forename: Thais P
authors.initials: TP
authors.lastname: Ferreira
authors.affiliation: Animal Parasitology Department, Federal Rural University of Rio de Janeiro, BR 465, km 7, 23897-000 Seropédica, RJ, Brazil.
authors.forename: Viviane S
authors.initials: VS
authors.lastname: Magalhães
authors.affiliation: Animal Parasitology Department, Federal Rural University of Rio de Janeiro, BR 465, km 7, 23897-000 Seropédica, RJ, Brazil.
authors.forename: Thais R
authors.initials: TR
authors.lastname: Correia
authors.affiliation: Animal Parasitology Department, Federal Rural University of Rio de Janeiro, BR 465, km 7, 23897-000 Seropédica, RJ, Brazil.
authors.forename: Fábio B
authors.initials: FB
authors.lastname: Scott
mesh_terms: D056810:Acaricides / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics; D000818:Animals; D001774:Blood Chemical Analysis / Q000662:veterinary*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D002851:Chromatography, High Pressure Liquid; D007279:Injections, Subcutaneous / Q000662:veterinary; D008297:Male; D011720:Pyrazoles / Q000008:administration & dosage* / Q000097:blood* / Q000493:pharmacokinetics; D011897:Random Allocation; D048494:Rhipicephalus; D013984:Tick Infestations / Q000188:drug therapy*; D016896:Treatment Outcome
chemical_list: D056810:Acaricides; D011720:Pyrazoles; C082360:fipronil
keywords: Phenylpyrazole; Subcutaneous administration; Tick