How Chocolate Makes Dogs Sick

Jennifer Coates, DVM
Published: March 30, 2012
How Chocolate Makes Dogs Sick

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You probably know that chocolate can make dogs sick, but do you know why? Understanding how this common canine toxin adversely affects a dog’s body underscores the importance of protecting dogs from exposure and helps explain the rationale behind a veterinarian’s treatment recommendations.

Chocolate contains substances known as methylxanthines (specifically caffeine and theobromine), which dogs are far more sensitive to than people. Different types of chocolate contain varying amounts of methylxanthines. In general, the darker the chocolate the more methylxanthines it contains and the more dangerous it is. For example, unsweetened baker’s chocolate contains up to 500 mg of methylxanthines per ounce, while dark semisweet chocolate is in the 155 mg/ounce range, and milk chocolate contains up to 66 mg/ounce.

Methylxanthines are stimulants that inhibit the activity of the enzyme phosphodiesterase. This enzyme is responsible for breaking down the substance cyclic adenosine monophosphate, which regulates a variety of metabolic processes. At low levels, chocolate intoxication will cause vomiting, diarrhea and hyper-excitability. Higher doses can result in nervous system dysfunction (e.g., seizures), irregular heart rhythms and even death. Dogs that ingest chocolate are also at risk for pancreatitis because of the high fat and sugar content of most of these products.

Answering the question, "Did my dog consume enough chocolate to make him sick?" requires knowing how much a dog weighs, what type of chocolate he got into and how much he ingested. Mild clinical signs of chocolate poisoning can be seen when a dog ingests around 9 mg of methylxanthines per pound of body weight. More severe problems occur when dogs get into 18 mg per pound body weight or more. So, if your dog weighs 20 pounds and ate 2 ounces of dark semisweet chocolate, the math works out to 155 mg methylxanthine per ounce of chocolate times 2 ounces divided by 20 pounds equaling 15.5 mg/pound, which is enough to cause a problem.

Because it is often difficult to determine exactly how much chocolate a dog has eaten, veterinarians typically assume the worst when making their calculations and tend to overestimate the amount of consumption. If it looks like your dog potentially could have ingested enough chocolate to make him sick, treatment is the safest way to proceed.

If treatment can be initiated within a couple of hours of a dog eating chocolate, inducing vomiting or performing a gastric lavage can remove significant amounts of the toxins before they are absorbed. Activated charcoal given by mouth can also attach to the methylxanthines, trapping them in the intestinal tract and prevent their absorption. Intravenous fluids may be given to support the body and prevent or treat dehydration. Dogs that develop seizures and/or cardiac arrhythmias require close monitoring and treatment with appropriate medications.

Chocolate can be a benign indulgence for people, but the same is not true for dogs. Feed your dog a nutritionally balanced food made from quality ingredients.

Dr. Jennifer Coates

Image: Chocolate Westie Dog / via The Chocolate House

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