Like people, most pet dogs find chocolate highly palatable. Unfortunately, chocolate contains stimulants that are toxic in high doses. Small dogs are at highest risk, since a relatively small amount of chocolate may contain more stimulant than they can handle.

How Chocolate is Harmful
Chocolate contains theobromine, a powerful stimulant related to theophylline (a respiratory medication) and caffeine. Chocolate also contains caffeine, but in much smaller quantities. Dark, unsweetened, and bakers chocolate have the highest concentration of theobromine. Milk chocolate, white chocolate, and confections that contain small amount of cocoa (such as cakes, cookies, and chocolate-coated candies) also contain the stimulant in lower levels.

Theobromine stimulates the central nervous system and the heart, increases blood pressure, and causes digestive upset. Signs of chocolate toxicity include excitement, agitation, or nervousness, thirst, vomiting, and diarrhea. Severe poisoning can result in loss of coordination, seizures, coma and death.

Diagnosis of Chocolate Poisoning
If you know that your dog has consumed chocolate, tell your veterinarian the quantity and the type of chocolate. The amount required to be toxic depends on the type of chocolate and the size of the dog. If your dog has consumed a dangerous amount, prompt treatment can reduce the likelihood of serious illness. Unfortunately, dogs sometimes get into chocolate and other poisons without their owners knowing. This can make accurate diagnosis much more difficult.

Treatment
If your pet can get to the veterinarian within 4-8 hours of eating the chocolate, it may be possible to prevent absorption of the toxin into the bloodstream. Emetics cause vomiting, which is removing the chocolate from the body when administered within four hours of exposure. A special absorbent medicine containing charcoal can be given up to eight hours after exposure. The charcoal binds to the chocolate in the intestine, preventing it from being absorbed and allowing it to be excreted in the feces. There is no specific antidote for theobromine, but animals that have already absorbed the toxin can benefit from IV fluids, heart medications, and anti-seizure drugs.

Preventing Chocolate Toxicity
Be sure to keep chocolate and all other potential poisons well out of reach of pets. Remember that unsweetened bakers chocolate is the most hazardous. Even though one or two M&Ms are not likely to be deadly, avoid the habit of feeding any amount of chocolate to your dog.