Possible chocolate poisoning in a dog
Travis Mays, MS, PhD
The TVMDL received a full set of fresh and fixed tissue samples and stomach content from a four-year-old Belgian Tervuren for testing. The dog appeared normal in the morning, running and playing in the yard. The owner found the dog deceased two hours later. It was noted that the dog liked to eat corn as it fell on the ground beneath a squirrel feeder and corn was observed in the stomach during the necropsy. There was also evidence the dog may have consumed some brownies the night before. Concerns were expressed about possible aflatoxicosis from the corn. Histopathology and a drug screen for unknowns were requested.
Histopathologic examination of the tissues did not reveal a specific cause of death, nor evidence of toxicity, including aflatoxicosis. Hepatic changes indicative of glycogen-type vacuolation, characteristic of steroid-induced hepatopathy, were observed.
Liver was extracted for the drug screen using a deproteinization procedure followed by enzyme hydrolysis. The extract was then subjected to a purification procedure using solid phase extraction (SPE). Testing was performed utilizing liquid chromatography – tandem mass spectrometry (LC-MS/MS). Theobromine, caffeine and theophylline were all detected in the liver by LC-MS/MS at estimated concentrations of 21 micrograms per gram (µg/g), 700 nanograms per gram (ng/g) and 263 nanograms per gram (ng/g), respectively. This finding confirms the dog consumed chocolate. It is challenging to correlate these drug concentrations in liver with the potential for toxicity. However, the high concentration of theobromine could have contributed to the death of this animal.
Methylxanthines are alkaloids that occur naturally in plants and are found in coffee beans, tea, and cocoa beans. The methylxanthines in chocolate include caffeine and theobromine. Methylxanthines are rapidly absorbed by mouth and metabolized in the liver. Methylxanthines undergo enterohepatic recirculation and can be reabsorbed via the bladder wall.1 The elimination half-life of methylxanthines varies widely by species. In dogs, the elimination half-life for theobromine, caffeine and theophylline are 17.5 hours, 4.5 hours, and 5.7 hours, respectively.1 The lethal dose of theobromine is reported to be 100-500 mg/kg of body weight in dogs.2 However, not all types of chocolate contain the same amount of theobromine. Clinical signs usually develop within 6-12 hours of ingestion and can include polydipsia, vomiting, diarrhea, restlessness, hyperactivity, cardiac effects, tachypnea, hypertension, and coma.1
1 DeClementi C. (2011, April 30). Managing Kitchen and Bathroom Hazards – Chocolate. Retrieved from https://www.dvm360.com/view/chocolate-proceedings.
2 Finlay F. and Guiton S. Chocolate Poisoning. BMJ. 2005, 331(7517):633.