Depletion and bioavailability of imidocarb residues in sheep and goat tissues

The residual depletion of a commercial product containing imidocarb dipropionate in sheep and goat tissues was investigated. Additionally, the oral bioavailability of residues was determined in rats to evaluate the extent to which tissue imidocarb residues could be reabsorbed by consumers. Ten ewes and 5 goats were administered im with a commercial formulation containing imidocarb dipropionate (Carbesia® cavalli, Shering-Ploug 121.15 mg/ml) at the single dose of 3 mg/kg bw corresponding to 2. 1 mg/kg bw imidocarb base. Two sheep and I goat were slaughtered 15, 30, 60, 90 or 120 d after dosing and samples of muscle, injection site muscle, liver, omental and subcutaneous fat, and kidneys were collected. Samples of cerebral hemisphere, cerebellum, olfactory bulb, pineal and pituitary glands were dissected. For the residue bioavailability study 7 groups of 3 Wistar rats each, were dosed by gavage with imidocarb dipropionate standard in water (group 2,3 and 4) or with imidocarb as a liver residue collected from prior dosed animals (group 5, 6 and 7) at 8.4, 16.8 or 33.6 μg/kg of imidocarb base respectively, for 5 d. Group I was control. All animals were sacrificed the day after the last drug administration and livers were collected. The highest drug levels in sheep and goats occurred in liver and kidney, suggesting that these tissues are targets for residues; muscle had negligible importance as storage tissue. Goats had a lower storage capability than sheep. The residue profile in sheep liver and omental fat showed a 30-d storage period to reach maximum concentrations, and suggested that imidocarb is redistributed. The high and long-lasting concentrations in brain showed its capacity to cross the blood-brain barrier and caused concern for potential neurotoxic effects. Detectable concentrations of imidocarb were not found in rat liver.