Intravenous fat emulsion as treatment for ivermectin toxicosis in three dogs homozygous for the ABCB1-1Δ gene mutation

Objective: To describe the outcome of 3 cases of ivermectin toxicosis in dogs homozygous for the ABCB1-1Δ gene mutation treated with intravenous fat emulsion (IFE). Series Summary: One Australian Shepherd and 2 Miniature Australian Shepherds were treated for naturally occurring ivermectin toxicosis with IFE. All 3 dogs were homozygous for the ABCB1-1Δ gene mutation. Serum ivermectin concentrations confirmed ivermectin exposure in each case. All 3 dogs exhibited tremors, ptyalism, and central nervous system depression, which progressed over several hours to stupor in 2 dogs, and to a comatose state requiring mechanical ventilation in the remaining dog. A 20% formulation of IFE^a was administered as an IV bolus (1.5 mL/kg) followed by a slow IV infusion (7.5-15 mL/kg [0.25-0.5 mL/kg/m], over 30 minutes). No change was observed in the neurologic status of any patient. Lipemia visible upon blood sampling persisted for 36 hours in 1 dog however, no other adverse effects were noted. Flumazenil (0.01 mg/kg IV), followed by a constant rate infusion(CRI) of 0.01 mg/kg/h IV was administered in 1 case, without any apparent clinical benefit or adverse effect. New or Unique Information Provided: IFE was ineffective in the treatment of ivermectin toxicosis in these ABCB1-1Δ homozygous mutant dogs. Further investigation is necessary to determine why IFE treatment was unsuccessful in these cases and whether its use can be optimized to yield better results.