In sufficient amounts, the theobromine found in chocolate is toxic to animals such as horses, dogs, parrots, cats (kittens especially), and other birds and small animals because they are unable to metabolize the chemical effectively. If they are fed chocolate, the theobromine will remain in their bloodstream for up to 20 hours, and these animals may experience epileptic seizures, heart attacks, internal bleeding, and eventually death.
According to the Merck Veterinary Manual 8th Edition Online approximately 1.3 g of baker's chocolate per kilogram of a dog's body weight (0.02 oz/lb) is sufficient to cause symptoms of toxicity. For example, a typical 25 gram baker's chocolate bar would be enough to bring out symptoms in a 20 kg dog.
Medical treatment involves inducing vomiting within two hours of ingestion, or contacting a veterinarian. Vets commonly treat seizure with diazepam or phenobarbitol, tremor with diazepam or methocarbamol, treat bradycardia with atropine, and treat tachyarrhythmia with propranolol, metoprolol or lidocaine.
The LD-50 (lethal Dose for 50% of a population) of theobromine in canines is 250 mg to 500 mg of theobromine per kilogram of body weight, although death has been documented at 115 mg of theobromine per kilogram of body weight. A typical 20 kg dog will normally experience intestinal distress after eating less than 240 g of milk chocolate, and won't necessarily experience bradycardia or tachyarrythmia unless it eats at least a half a kilogram of milk chocolate. If it does not expel the chocolate from its system because of the fat and sugar content, then it would have a 50% chance of surviving after eating 5 kg of milk chocolate. Dark, sweet chocolate has about 50% more theobromine and thus is more dangerous to dogs.
