PLASMA PHARMACOKINETIC PROFILE OF FIPRONIL 1% POUR-ON IN GOATS.

Fipronil shows 800-fold higher systemic exposure in goats than cattle, requiring species-specific safety assessment.

This pharmacokinetic study evaluated fipronil 1% pour-on formulation in eight Alpine Brown goats following topical administration at 1 mg/kg. Using HPLC analysis with blood sampling over 117 days, researchers characterized plasma concentrations of fipronil and its primary metabolite, fipronil sulfone. Fipronil demonstrated rapid plasma detection (Cmax 443.7 ± 195.8 ng/mL), extensive distribution, and terminal elimination with a half-life of 4.2 ± 0.8 days and AUC of 1245.3 ± 312.5 ng·day/mL. Fipronil sulfone showed delayed formation with lower peak concentration (67.3 ± 27.3 ng/mL), Tmax of 15.0 days, and AUC of 558.4 ± 92.1 ng·day/mL. No adverse clinical effects or significant biomarker changes occurred. Notable findings include systemic exposure substantially higher (>800-fold) than reported in cattle, indicating significant species-specific differences in dermal absorption. The prolonged persistence and delayed metabolite formation suggest flip-flop kinetics governed by slow redistribution from skin and adipose reservoirs. This first characterization of fipronil pharmacokinetics in goats provides essential background for future residue depletion studies and food safety assessments.

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