Management of Eprinomectin Neurotoxicosis in Cats

OBJECTIVE: To provide a resource for managing eprinomectin neurotoxicosis in cats, emphasizing the unique aspects of this particular macrocyclic lactone. ETIOLOGY: The label dose of eprinomectin-containing parasiticides causes neurotoxicosis in P-glycoprotein-deficient cats. DIAGNOSIS: Diagnosis of eprinomectin-induced neurotoxicosis relies on history, paying particular attention to recent drug administration, and a physical examination that includes a neurologic assessment. Mydriasis, ataxia, generalized weakness, and glossal paresis are typical clinical signs. MDR1 genotyping can provide supportive evidence. Blood work is typically normal. THERAPY: There is no antidote for eprinomectin toxicosis. Intravenous lipid emulsion may not be effective in patients homozygous for the MDR1 mutation. Prolonged supportive therapy is indicated, keeping in mind that glossal paresis is characteristic of eprinomectin toxicosis and requires nutritional support that bypasses the oral cavity. Drugs that are either CNS depressants or P-glycoprotein substrates may exacerbate or prolong toxicosis and should be avoided. PROGNOSIS: Although it generally takes several weeks for neurologic signs to fully resolve, with appropriate supportive care, complete recovery from eprinomectin toxicosis with no residual neurologic deficits can be achieved.