Chocolate poisoning in dogs: Symptoms and treatments

The nutritional requirements of a dog differ from that of a human and some foods that are quite acceptable for humans cause a dog a great deal of harm. Chocolate, that tasty treat we enjoy, contains caffeine and theobromine (3,7-dimethylxanthine) both of which are methylxanthines. Methylxanthines are toxic for dogs affecting their heart and nervous system. Chocolate contains more theobromine than it does caffeine.

The amount of methylxanthines causing problems to a dog depends on the size of the dog and its sensitivity to the chemical. The LD 50 of is between 100 and 200 mg/kg body weight (LD 50 – lethal dose 50 the quantity of a chemical that will kill 50% of the animals given that dosage). A lethal dose for a dog weighing 10 kg would be in the range of 1000 to 2000 mg.

Much smaller dosages still adversely affect a dog. Ingesting about 20 mg/kg body weight of methylxanthines, causes diarrhea, vomiting and excessive thirst in a dog. An increase to about 40-50 mg/kg body weight affects the dog’s heart.  A dose in excess of 60 mg/kg body weight causes seizures.

So how much of these chemicals does a bar of chocolate contain. That depends on the type of chocolate. The rich dark unsweetened chocolate used in baking contains approximately 16 mg/g, sweetened dark chocolate 5.4 - 5.7 mg/g, milk chocolate about 2.3 mg/g and the amount of methylxanthines in white chocolate is insignificant. Dry cocoa powder contains about 28.5 mg/g of methylxanthines. Cocoa bean husks, sometimes used as garden mulch, contain 9.1 mg/g, so if you are a dog owner stick to another form of mulch because chocolate toxicosis of dogs occurs from this source of methylxanthines.

Signs of chocolate toxicosis appear within 6 -12 hours of the animal ingesting the chocolate. Early signs include diarrhea, vomiting, excessive thirst, restlessness and abdominal swelling. The dog then starts to urinate excessively, show signs of hyperactivity as well as jerky movements, tremors and even seizures. Veterinary examination reveals heart arrhythmias, a low body temperature and low blood pressure. A blood test frequently reveals a low blood potassium level.

The methylxanthines are metabolized in the liver and excreted by the kidneys. Caffeine has a half-life in the dog of 4.5 and theobromine a half-life of 17.5 hours. Treatment of a dog with chocolate toxicosis involves keeping it stable unit it is able to excrete the chemicals poisoning its system. Taking a dog to a veterinarian as soon as chocolate ingestion is suspected maximizes the animal’s chance of survival. The vet may induce vomiting and give the dog activated charcoal to prevent some of the chemicals being absorbed from the intestines. Insertion of a urinary catheter ensures rapid bladder emptying preventing resorption of the methylxanthines via the bladder wall. Intravenous drugs control the tremors and seizures as well as stabilizing the heart. A heating pad maintains the dog’s temperature. Blood potassium levels require monitoring and electrolyte solution administered if they drop to a dangerous level.

Prevention is better than cure so never feed your dog chocolate as a treat. There are plenty of suitable dog treats available. Keep all sweets meant for human consumption away from the dog. 

Reference Sources:

Merck Veterinary Manual

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