Theobromine poisoning

Animal	Oral toxicity (mg/kg)
	TDLo	LD50
Cat		200
Dog	16	300
Human	26	~1,000
Mouse		837
Rat		1,265

Structure of theobromine (IUPAC name: 3,7-dimethyl-1H-purine-2,6-dione)

Theobromine poisoning or chocolate poisoning is an overdose reaction to the xanthine alkaloid theobromine, found in chocolate, tea, cola beverages, açaí berries, and some other foods. Lethal (LD₅₀) doses of theobromine have only been published for humans, cats, dogs, rats, and mice; these differ by a factor of 6 across species (see the table in this article).

Chocolate

In humans

Cocoa beans contain about 1.2% theobromine by weight, so an ounce (28g) of raw cacao contains approximately 0.3g theobromine. Processed chocolate, in general, has smaller amounts. The amount found in highly refined chocolate candies (typically 1.4–2.1 g/kg or 40–60 mg/oz) is much lower than that of dark chocolate or unsweetened baker's chocolate (> 14 g/kg or > 400 mg/oz). In general, the amount of theobromine found in chocolate is small enough such that chocolate can be safely consumed by humans. However, occasional serious side effects may result from the consumption of large quantities, especially in the elderly.

In other species

Serious poisoning happens more frequently in domestic animals, which metabolize theobromine much more slowly than humans, and can easily consume enough chocolate to cause chocolate poisoning. If large numbers of filled chocolate candies are consumed, another serious danger is posed by the fat and sugar in the fillings, which can sometimes trigger life-threatening pancreatitis several days later. The most common victims of theobromine poisoning are dogs, for which it can be fatal. The toxic dose for cats is even lower than for dogs. However, cats are less prone to eating chocolate since they are unable to taste sweetness. Theobromine is less toxic to rats, mice, and humans, who all have an LD₅₀ of about 1,000 mg/kg.

In dogs, the biological half-life of theobromine is 17.5 hours; in severe cases, clinical symptoms of theobromine poisoning can persist for 72 hours. Medical treatment performed by a veterinarian involves inducing vomiting within two hours of ingestion and administration of benzodiazepines or barbiturates for seizures, antiarrhythmics for heart arrhythmias, and fluid diuresis. Theobromine is also suspected to induce right atrial cardiomyopathy after long term exposure at levels equivalent to ~15 g of dark chocolate per kg of weight and per day. According to the Merck Veterinary Manual, baker's chocolate of approximately 1.3 g/kg (0.02 oz/lb) of a dog's body weight is sufficient to cause symptoms of toxicity. For example, 0.4 ounces (11 g) of baker's chocolate would be enough to produce mild symptoms in a 20-pound (9.1 kg) dog, while a 25% cacao chocolate bar (like milk chocolate) would be 25% as toxic as the same dose of baker's chocolate. One ounce of milk chocolate per pound of body weight is a potentially lethal dose in dogs.

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

Symptoms

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.

See also

• Xanthine oxidase

References

• Theobromine in the ChemIDplus database (September 9, 2004)
• Merck Veterinary Manual (Toxicology/Food Hazards section), Merck & Co., Inc., Chocolate Poisoning. (June 16, 2005)

External links

• Chocolate Toxicity Calculator
• Dog Chocolate Toxicity Meter
• A Pet Owner's Guide to Poisons: Chocolate at the Wayback Machine (archived August 5, 2009)
• Toxicity basic facts