Bromethalin is a neurotoxin found in rodenticides. Bromethalin toxicity leads to a decrease in adenosine triphosphate production, which affects the sodium/potassium pumps throughout the body and causes electrolyte imbalances. Fluid shifts subsequently occur in myelinated areas in the brain and spinal cord, leading to cerebral edema and associated neurologic signs and possible death. 

Two distinct syndromes (ie, paralytic and convulsant) have been reported with bromethalin ingestion.^1,2 Paralytic syndrome occurs 1 to 7 days after ingestion of a sublethal dose (1.67-2.5 mg/kg). Clinical signs include vomiting, tremors, mild to severe ataxia, paresis, and possible paralysis. Convulsant syndrome occurs after ingestion of a larger dose (3.65-6.25 mg/kg), and clinical signs (eg, circling, hyperthermia, hyperesthesia, seizures, depression, death) develop within 4 to 18 hours.

This retrospective study reviewed records of 192 dogs with bromethalin ingestion. Twenty-five dogs developed clinical signs, 5 of which were initially presented with severe neurologic signs similar to convulsive syndrome; these 5 dogs were euthanized within 12 hours of admission. Fifteen out of the 25 dogs were described as having mild to moderate clinical signs (eg, vomiting, diarrhea, anorexia, lethargy), and the remaining 5 dogs developed neurologic signs (eg, ataxia, tremors, seizures). These 20 dogs survived to discharge. GI decontamination with emesis and single and multiple doses of activated charcoal were the most common treatments used. Additional treatments included antiemetics, gastroprotectants, IV fluids, methocarbamol, anticonvulsants, IV lipid emulsion, and mannitol. The survival rate for this patient group was 97.4%.

Key pearls to put into practice:

Early decontamination with emesis and multiple doses of activated charcoal should be recommended for patients presented after bromethalin ingestion.

Delayed paralytic syndrome should be considered in vague, nonspecific cases in which toxicity is suspected.

Intralipid emulsion therapy should be considered in bromethalin toxicosis patients with clinical signs. IV lipid emulsion use in these patients warrants further investigation.