Theobromine poisoning

Theobromine poisoning or chocolate poisoning is an adverse reaction to the alkaloid theobromine, found in chocolate, tea, cola beverages, and some other foods. Cacao beans contain about 1.2% theobromine by weight, while processed chocolate generally has smaller amounts. The amount found in highly refined chocolate candies (typically 40-60 milligrams per ounce or 1.4 to 2.1 grams per kilogram) is much lower than that of dark chocolate or unsweetened baker's chocolate (over 400 mg/oz or 14 g/kg).

The amount of theobromine found in chocolate is small enough that chocolate can be safely consumed by humans (and other Apes) in large quantities, but animals that metabolize theobromine more slowly can easily consume enough chocolate to cause chocolate poisoning. The most common victims of theobromine poisoning are dogs (for which it can be fatal). Cats and especially kittens are yet more sensitive, and many other animals are also susceptible.

The first signs of theobromine poisoning are nausea, vomiting, diarrhea, and increased urination. These can progress to cardiac arrhythmias, epileptic seizures, internal bleeding, heart attacks, and eventually death.

Theobromine is especially toxic to horses, dogs, parrots, voles, and cats 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. Medical treatment involves inducing vomiting within two hours of ingestion and contacting a veterinarian.

A typical 20 kg dog will normally experience intestinal distress after eating less than 240 g of dark chocolate, but won't necessarily experience bradycardia or tachyarrhythmia unless it eats at least a half a kilogram of milk chocolate. According to the Merck Veterinary Manual, 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.

Chemists with the USDA are investigating the use of theobromine as a toxicant to control coyotes that prey on livestock.