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.

The effect of cattle-administered ivermectin and fipronil on the mortality and fecundity of Anopheles arabiensis Patton

“…For formulations typically used in recent years, the maximum concentration of subcutaneously injected ivermectin was reached at day 1 while the minimum was reached after 25 days [ 61 ]. Similarly, fipronil injected in cattle reached its maximum and minimum concentrations rapidly within 24 h [ 62 ]. In a study where the pour-on fipronil formulation was administered in cattle to investigate its effect against ticks, the mean plasma concentration values over time varied, with the maximum concentration of 73.7 g/l reached after 2.5 days [ 63 ].…”

“…The pour-on fipronil concentration reached its half-life at day 19 and decreased slowly until its minimal level at day 40 [ 63 ]. Topical treatment results in exposure to environmental degradation, such as mechanical removal by rain [ 62 ]. Factors such as body weight, nutrition type and physiological status also lead to variation in drug concentrations within individuals of the same species [ 59 ].…”

The effect of cattle-administered ivermectin and fipronil on the mortality and fecundity of Anopheles arabiensis Patton.

“…For formulations typically used in recent years, the maximum concentration of subcutaneously injected ivermectin was reached at day 1 while the minimum was reached after 25 days [42]. Similarly, pronil injected in cattle reached its maximum and minimum concentrations rapidly within 24 hours [43]. In a study where the pour-on pronil was administered in cattle to investigate its effect against ticks, the mean plasma concentration values over time varied and maximum concentration was 73.7 g/L reached after 2.5 days [44].…”

“…The pour-on pronil concentration reached its half-life at day 19 and decreased slowly until minimal level at day 40 [44]. Topical treatment results in exposure to environmental degradation such as mechanical removal by rain (Cid et al 2016). Factors such as body weight, nutrition type and physiological status also lead to variation in drug concentrations within individuals of the same species [41].…”

Injectable eprinomectin for cattle: Tick efficacy and pharmacokinetics

“…The topical route of administration, although very common, may have some disadvantages such as mechanical removal of the product by licking between treated cattle (Aguirre et al, ) or environmental action (rain or sunlight) (Davey, George, Hunter Lii, & Jeannin, ), leading to issues related to efficacy variability inter‐individuals and environmental impact. The injectable route could overcome some of these problems, as well as being preferred by the owners (Cid, Ferreira, Magalhães, Correia, & Scott, ).…”