Chocolate is Sweet...But Can Be Deadly

Oct 23, 2012

Chocolate contains theobromine, an alkaloid similar to caffeine, which can be toxic to animals if fed to excess.  Most dangerous is baking chocolate, which contains almost ten times the amount of theobromine that ordinary milk chocolate does. One ounce of baking chocolate or a 2 kg bag of chocolate pieces can be life-threatening to a 5 kg dog. Put another way, the ingestion of approximately one-half kilogram (1.5 pounds) of milk chocolate would result in a potentially lethal dose for a 12 kg (25 pound) dog.

Dogs are more likely to become poisoned by eating chocolate than cats, probably because they like the sweet taste of chocolate and because cats tend to be fussier than dogs about what they will eat.  Even small amounts of chocolate can cause adverse reactions. Reactions can include vomiting and diarrhea, restlessness, irregular heartbeat, hyperactivity, and frequent urination.  These signs usually appear about 4-5 hours after ingestion. More severe signs of chocolate toxicity include tremors, seizures, and death. Clinical signs may not appear for several hours after ingestion and complete recovery after veterinary care may take several days.  
Toxicity studies have shown that compared to other species, dogs are unusually sensitive to theobromine. This is because they have a low rate of theobromine metabolism, which causes theobromine to stay in the blood steam for a longer time.  After a single dose, the half-life of theobromine in adult dogs is 17.5 hours, compared to six hours in human subjects. This may also be the case in cats.
There is no danger in giving the occasional small treat of chocolate to a dog. However, if presented with an opportunity, most pets will tend to overconsume chocolate. For this reason, all foods containing chocolate should be safely stored away in areas inaccessible to pets. If your pet accidentally ingests chocolate, consult your veterinarian immediately for advice.