Overingestion of methionine tablets by a dog

Methionine tablets are used as urinary acidifiers for pets and to decrease damage from dog urine to lawns. A 39-kg Labrador Retriever ingested approximately 350 tablets containing 150 mg methionine/tablet and was presented after repeated episodes of vomiting. The only abnormality was posterior ataxia suggestive of spinal cord injury. The animal was treated with i.v. fluids, steroids and gastrointestinal protectants. Approximately 4.5 h after entering the clinic the dog had a single seizure episode lasting 2-3 min which was treated with phenobarbital. Serum ammonia at that time was normal (0.19 mg/dL). The animal did not show further CNS abnormalities and awoke apparently normal. A musty odor to the breath was noticed through the course of the day, possibly due to volatile mercaptans produced from methionine metabolism. The animal made an uneventful recovery and was discharged the next day.