Clinical effects of brimonidine ophthalmic drops ingestion in 52 dogs

Brimonidine is an ophthalmic solution of 0.2% brimonidine tartrate used to lower intraocular pressure in human glaucoma patients. A retrospective study was conducted of brimonidine ophthalmic solution ingestion in 52 dogs reported to the ASPCA Animal Poison Control Center between January 1998 and December 2000. Eighty percent of the dogs were < 1-y of age. Approximate ingested dosages ranged from 0.18-5.55 mg/kg. Incidence of clinical signs were bradycardia (67%), depression (46%), ataxia (27%), hypotension (25%), pallor (23%), weakness (17%), change in mucous membrane color (17%), hypothermia (13%), vomiting or retching (13%.). Shock, weak pulses, and poor capillary refill time were also reported. Treatment involved early decontamination, supportive care, andyohimbine and atipamezole as specific alpha-2 antagonists that could be helpful in reversing the effects of brimonidine. Due to the possibility of severe cardiovascular effects developing, the ingestion of brimonidine ophthalmic solution in dogs should be considered dangerous.