Pharmacokinetic studies were conducted using [14C]- and unlabelled bifenthrin to characterize disposition in rats.  Following oral administration of [14C]bifenthrin at 5 mg/kg, a majority of the dose (>80%) was excreted fairly rapidly (within 48 hrs) . After an oral dose of 3.1 mg/kg of cold bifenthrin, the Cmax levels were 83 and 361 ng/g in brain (6 hr) and plasma (2 hr). Following intravenous administration (1 mg/kg), bifenthrin plasma clearance (CL = 37/mL/min/kg) and elimination (t1/2 = 13.4 hrs) were relatively moderate to rapid. The t1/2 in brain was 11.1 hrs. The neurotoxic effects (reduction in locomotor activity) have previously been shown to be proportional to bifenthrin concentrations in brain and/or plasma. Elimination kinetics, determined for the first time by intravenous injection, show that the concentrations could rapidly decline below the threshold level from both compartments. Therefore, the reversibility of neurotoxicity correlates well with the elimination kinetics of bifenthrin.

Pharmacokinetic properties of bifenthrin in rats explain reversibility of neurotoxicity

248th National Meeting (2014)

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