|Animal||Oral toxicity (mg/kg)|
Theobromine poisoning or chocolate poisoning is an overdose reaction to the 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).
Cocoa beans contain about 1.2% theobromine by weight, while 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.
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 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. A typical 20 kg (44 lb) dog will normally experience intestinal distress after eating less than 240 g (8.5 oz) of dark chocolate, but won't necessarily experience bradycardia or tachyarrhythmia unless it eats at least 0.5 kg (1.1 lb) of milk chocolate. 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, 2.25-ounce (64 g) of baker's chocolate would be enough to produce symptoms in a 20-pound (9.1 kg) dog, while a 60% cacao chocolate bar be 60% as toxic as the same dose of baker's chocolate; however, other types of chocolate (such as milk chocolate candies) contain significantly less theombromine and so require the dog to ingest more before showing 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.
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- THEOBROMINE from the Hazardous Substances Data Bank
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- Theobromine in the ChemIDplus database (September 9, 2004)
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