This nonanticoagulant, single-dose rodenticide is a neurotoxin that appears to uncouple oxidative phosphorylation in the CNS. CSF pressure increases, which places pressure on nerve axons and results in decreased conduction of nerve impulses, paralysis, and death. In dogs, a dose of 1.67 mg/kg is toxic, and 2.5 mg/kg (25 g of bait/kg body wt) is lethal.

Bromethalin can cause either an acute or a chronic syndrome. The acute effects follow consumption of ≥5 mg/kg bromethalin. Signs, which include hyperexcitability, muscle tremors, grand mal seizures, hindlimb hyperreflexia, CNS depression, and death, may appear ~10 hr after ingestion. Chronic effects are seen with lower dosages and may appear 24–86 hr after ingestion. This syndrome is characterized by vomiting, depression, ataxia, tremors, and lateral recumbency. The effects may be reversible if exposure to bromethalin is discontinued. Bromethalin toxicosis should be considered when cerebral edema or posterior paralysis is present.

Treatment should be directed at blocking absorption from the gut and reducing cerebral edema. Use of mannitol as an osmotic diuretic and corticosteroids have been suggested but have shown little effect in dogs poisoned by bromethalin. Use of activated charcoal for several days may improve the recovery rate.

Last full review/revision March 2012 by Frederick W. Oehme, DVM, PhD