|Animal||Oral toxicity (mg/kg)|
Theobromine poisoning, also incorrectly called chocolate poisoning, is an overdosage reaction to the xanthine alkaloid theobromine, found in chocolate, tea, cola beverages, and some other foods. Median lethal (LD50) doses of theobromine have only been published for cats, dogs, rats, and mice; these differ by a factor of 6 across species. At doses of 0.8-1.5 g (50-100 g cocoa) per day sweating, trembling and severe headaches were noted. Limited mood effects were shown at 250mg/day and negative mood effects above.
Cocoa beans contain about 1.2% theobromine by weight, so an ounce (28g) of raw cocoa contains approximately 0.3g theobromine. Processed chocolate, in general, has smaller amounts. The amount found in highly refined chocolate candies or sweets (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 with a negligible risk of poisoning.
In other speciesEdit
Serious poisoning happens more frequently in domestic animals, which metabolize theobromine much more slowly than humans, and can easily consume enough chocolate to cause poisoning. 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.
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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