Chemical Assay for Ivermectin in Edible Tissues

Abstract

For any animal drug a chemical assay is needed to demonstrate the reduction of drug amounts in edible tissues to negligible levels at appropriate times after the administration of the drug. In the case of ivermectin this was a particular analytical challenge. Because ivermectin is very potent, it is dosed at quite low levels, typically 0.2 mg/kg: hence the residues, even immediately following dosing, are in the parts per billion (ppb) level. Further, the no-effect level (NOEL) of 0.2 mg/kg in animal safety studies results in negligible residues being defined as 10 to 20 ppb for many tissues. Since an acceptable analytical method must provide reliable data at the negligible residue level, the actual analytical method should have a limit of detection approximately tenfold lower than the negligible level.