Pet Chat
by Jennifer Faul

I love autumn. Apples and pumpkins abound, with a crisp freshness in the air that makes my dog beg for longer walks each day, which I am happy to concede to. It is the beginning of the season of celebrations, and many celebrations – with lots of chocolate – are upon us. While many argue that some amount of dark chocolate is good for people, there is no amount of chocolate that is good for our pets. 
Chocolate contains caffeine and theobromine, both of which are methylxanthines. Xanthines are compounds that occur naturally in our bodies and in plants. Compounds such as caffeine (found in coffee, soda and cocoa bean mulch), theophylline (found in tea) and theobromine (found in chocolate) are methylated derivatives of xanthines. Biochemically speaking, this means that a hydrogen atom is replaced by a methyl group.  Practically speaking this change in chemistry creates compounds that can have devastatingly toxic, or even lethal, effects on our pets. 
Dogs, especially, love the smell of chocolate and seem to seek it out.  And often times they get into candy bars at this time of year and are seemingly unaffected by them. So how come some pets seem to tolerate chocolate and how much is too much?  Since chocolate toxicity begins at 100 milligrams of chocolate ingested per kilogram of body weight, smaller pets are at greater risk, and “stronger” types of chocolate cause toxicity in smaller amounts. Milk chocolate is the “safest” to ingest since it contains the lowest dose of theobromine. Considering that the average chocolate bar contains three ounces of milk chocolate, it would take two candy bars to produce toxicity in a ten-pound dog. However, a single ounce of baking chocolate could produce severe toxicity in the same size dog.
The following are toxic doses of chocolate:
• 1 ounce per pound of body weight for milk chocolate (60 ounces for a 60-pound dog)
• 1 ounce per 3 pounds of body weight for semi-sweet chocolate (20 ounces for a 60 pound dog)
• 1 ounce per 9 pounds of body weight for baker’s chocolate. (7 ounces for a 60-pound dog).
 Chocolate was first made 2,000 years ago by the ancient peoples of Mexico and Central America. The Maya and Aztec peoples pressed the seeds from the pods of the cacao tree and, adding spice and seasoning, made a bitter foamy drink. The effects of the methylxanthines, to relax smooth muscle, stimulate diuresis, and act as cardiovascular and nervous system stimulants, were documented. Drinking chocolate was a central cultural theme. 
These same effects that we are so familiar with can lead to extreme symptoms in cases of toxicity: anxiousness, irritability, hyper-excitability, racing heart rates, restlessness, muscle tremors, increased urination, vomiting and diarrhea. When a dog or cat ingests chocolate, the theobromine ingredient causes the release of large amounts of epinephrine in a dog’s body; this causes an increase in the dog’s heart rate and can lead to heart arrhythmias. Gastro-intestinal (GI)signs or hyperactivity are often seen in the first few hours after ingestion; these can soon lead to hyperthermia, muscle tremors, seizures, coma and even death.
Avoidance is always the best policy.  Any amount of chocolate can be too much and should be considered as detrimental to our pets. Never intentionally feed your dog chocolate, coffee or soda. Put those giant bags of Halloween candy in a cupboard and out of reach. Dogs love the sweet smell of chocolate. They will seek it out and often they will eat all the wrappers too.
Several years ago, there was a lot of discussion about cocoa bean mulch after a dog in Minnesota died after consuming some of it. Avoid using this type of mulch if you have pets that like to chew on bark or sticks in your yard. If you do suspect your dog has ingested any amount of chocolate, it is always best to consult your veterinarian right away. Your pet may be made to vomit, may require supportive care for GI upset or pancreatitis, or may need to be hospitalized. As Halloween fast approaches, with the other sweet holidays in tow, chocolate becomes a mainstay of our diets. Just be sure to stick to pet food and pet-appropriate treats for your pets!
Jennifer Faul is a practicing small animal veterinarian, visiting Charlotte as the owner and practitioner of Vermont Veterinary Housecalls.