Ivermectin Toxicosis in Dogs: A Retrospective Study

Ivermectin is a commonly used veterinary drug that may cause serious problems in overdose situations. A retrospective study was completed, which evaluated canine exposures to ivermectin from 1998 to 2005. The cases were evaluated based on ivermectin dosage, clinical signs seen, signalment of the animal involved, and the potential that the animal could have a p-glycoprotein defect. Results showed that clinical signs may be seen in some animals at doses lower than previously reported. Some dogs may have p-glycoprotein defects or other reasons for increased susceptibility to ivermectin toxicosis. The clinician should be aware that clinical signs may develop even at dosages previously thought to be of little risk (e.g., 0.2 to 2.5 mg/kg in breeds historically considered to have normal p-glycoprotein function).