Musings of a Veterinarian

Chocolate Toxicity

April 15, 2009 By: Dr. K Category: General

ChocolateMany veterinarians have answered the phone call from a panicked dog owner worried about Fido after he emptied the candy dish of chocolates. But how concerned should you really be? Most people have heard chocolate is toxic to dogs but many myths still surround the subject. Would you believe ingestion of large amounts of chocolate can prove toxic to humans as well?

The toxic principle behind chocolate involves how quickly its chemicals are metabolized by the body. The toxic compound in chocolate is theobromine. Theobromine is a methylxanthine derivative in the same family as caffeine and the respiratory medication theophylline. Methylxanthine compounds are found in some foods and plants, including the cacao plant, as well as in human and animal medications. Methylxanthines inhibit adenosine receptors leading to vasoconstriction, tachycardia, and central nervous system stimulation. These signs are frequently observed with the “caffeine rush” we get with our morning coffee: increased heart rate, blood pressure, and mental alertness. They also inhibit phosphodiesterase thus increasing cyclicAMP leading to increased catecholamine release. Catecholamines are hormones released from the adrenal glands in response to stressful events. The most common of these hormones is epinephrine (adrenaline). The effects of excessive catecholamine release manifest as vomiting and diarrhea, hyperactivity and hyperreflexivity, cardiac arrhythmias, tremors, seizures and even death. Humans metabolize theobromine much more effectively than dogs due to unknown biochemical differences.  Theobromine can accumulate in the dog’s system, making it more susceptible to intoxication.

methylxanthine_chartMethylxanthine levels vary based on type of chocolate with concentrations typically greater in darker chocolates. The minimal lethal methylxanthine dose in dogs is reported as 100-200 mg/kg. The reported potential lethal dose equates to about 7 grams of baker’s chocolate or 60 grams of milk chocolate per kilogram of dog’s weight. A regular sized Hershey Milk Chocolate bar is 43 grams containing about 86mg of methylxanthines. A 20lb dog would need to consume about 10 Hershey bars to reach deadly levels of methylxanthines. However, that same dog may only require consumption of 56 grams  (about 2 oz) of baker’s chocolate to achieve a lethal dose.  Gram to ounce conversion table.

Dogs who have potentially consumed a toxic amount of chocolate should see a veterinarian immediately. Emesis (vomiting) may be induced to prevent further theobromine absoprtion. Animals with seizures, intractable vomiting, or cardiac abnormalities will need more intensive care.

An occasional Hershey Kiss probably won’t affect your dog’s well being. Just try to keep the pan of brownies from Fido’s reach.

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