Is it true that animals can be poisoned by eating chocolate?
Yes, well sort of, it depends, is that clear? Actually chocolate poisoning is not unusual in dogs, maybe because many dogs will eat almost anything. Cats are more discerning. I found one reported case of chocolate poisoning in a horse. That is weird because the toxic dose of chocolate is dependent on body weight.
The published toxic dose is 100-200 mg/kg. (a mg, milligram, is 1/1000 of a gram, a kg, kilogram, is 1000 grams, a kilogram is equal to 2.24 pounds, 16 ounces to the pound. Let your fourth grader do the math.) To complicate matters, veterinarians at the Poison Control Center of the ASPCA have reported problems with doses as low as 20mg/kg, of theobromine. So we will go with the lower toxic dose.
Chocolate comes from the beans of the cacao tree. The beans contain methylxanthines, a class of drugs that include theobromine and caffeine. Most humans can metabolize, break down, both theobromine and caffeine without much difficulty, in two to four hours. The half-life of theobromine in dogs is 17.5 hours, the half-life of caffeine about 4.5 hours, about the same in cats.
To complicate matters further, the levels of theobromine depend upon the type of chocolate. Dry cocoa powder has the most theobromine, about 800 mg/ounce. If your five-pound Chihuahua (about 2.25 kg) ingests an ounce of cocoa powder, he will have ingested 800 mg of theobromine. Anything more than 45 mg could cause problems for him. Unsweetened Baker’s chocolate contains about 450 mg/oz of theobromine, an ounce is still very toxic to your Chihuahua. Semisweet and sweet dark chocolate contain about 150-160 mg/oz and milk chocolate about 44-64 mg per oz so your Chihuahua could still be in trouble. However, your 70-pound Golden Retriever (much more likely to snarf down your chocolate) will have to consume about 14-16 oz of milk chocolate to get sick on it.
A 400-kg horse would need to ingest about 8,000 mg of theobromine; that’s about 17-18 oz of Baker’s chocolate. If caught feeding Baker’s chocolate to a race horse you will be banned from the track, maybe prosecuted, it’s considered a stimulant. White chocolate contains very small quantities of the methylxanthines.
Both caffeine and theobromine are readily absorbed from the gastrointestinal tract and distribute throughout the body. Both compounds are metabolized in the liver. The metabolites are excreted in the urine along with small amounts of the original, un-metabolized, compounds. So, if your pet is old, or has liver or kidney disease, the toxic effects can be intensified. With normal liver and kidney function, it will take about two days for your pet to eliminate a toxic dose from its system.
Signs of chocolate toxicity in dogs and cats include diarrhea, vomiting, increased urination, muscle twitching, excessive panting, hyperactivity, whining and — when severe — seizures, rapid heart rate and circulatory collapse. Treatment is to induce vomiting and use activated charcoal in an attempt to bind the theobromine and prevent its absorption from the GI tract. You can induce vomiting with 1-2 teaspoons of hydrogen peroxide, repeated two or three times every 15 minutes, if needed. One to three teaspoons of syrup of Ipecac, based on the size of the pet, will also do the trick.
If your pet is showing signs of intoxication, get it to your veterinarian. S/he can sedate the animal to control seizures and flush with intravenous fluids to hasten elimination from the body.
Dr. David Gross of Edmonds graduated from Colorado State University’s veterinary school in 1960 and was in private practice for 10 years. He retired in 2006 as Professor and Head of Veterinary Biosciences, at the University of Illinois, Urbana-Champaign. Dr. Gross is the author of “Animals Don’t Blush,” which describes the unique patients and even more unique clients of a veterinary practice in Sidney, Montana in the early 1960s. The book is available at the Edmonds Bookshop.