A review of moxidectin overdose cases in equines from 1998 through 2000.

Moxidectin is a macrolide endectocide available as a 2% equine oral gel in the US. This report presents clinical signs of moxidectin toxicosis and its treatment in equines as reported to the ASPCA Animal Poison Control Center (APCC) from January 1998 to December 2000. Nine cases of moxidectin overdose in equines occurred: 5 had signs of toxicosis such as coma, dyspnea, depression, ataxia, tremors, seizures, or weakness. The approximate dose of moxidectin at which these signs were observed ranged from 1.0 to 5.1 mg/kg. The 4 equines that ingested moxidectin between 0.9 mg/kg to 1.7 mg/kg did not show signs of toxicosis. Clinical signs were seen within 6-22 h and lasted for 36-168 h. Only 1/5 clinical equines was an adult, the others were < 4 month of age. This study supports earlier report that young foals are more susceptible to moxidectin toxicosis. All 4 equines with known outcomes recovered with treatment that included decontamination, seizure control, thermoregulation, fluid therapy, and supportive care.