Chocolate Poisoning in Dogs

To most of us, chocolate is a delicious sweet brown substance, with no more problems than an expanding waistline and rotting teeth. To dogs, chocolate is also delicious, but potentially lethal. The humble cocoa bean, from which chocolate is produced, contains a drug called theobromine. This is closely related to caffeine, which chocolate also contains. The toxicity of chocolate for dogs is due to its theobromine content. This long lasting very potent toxin that can cause death is unfamiliar to most people who may not worry too much if their dog is sick after eating a quantity of chocolate. Chocolate poisoning is very serious and many dogs die every year from this toxin. It is the most common poisonings that occur in dogs in the UK.

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Types of Chocolate

The different forms of chocolate and its by-products contain different amounts of theobromine. The following list is in decreasing order of quantity of theobromine

1. Cocoa beans (30mg/gm chocolate)
2. Cocoa powder (20mgs/gm chocolate)
3. Dark chocolate (15mgs/gm chocolate)
4. Milk chocolate (2mgs/gm chocolate)
5. Drinking chocolate (0.5mgs/gm chocolate)
6. White chocolate

The majority of cases of serious poisoning incidences ( in the UK) involve the European (continental) types of chocolate, as these contain more cocoa and less milk. There have been many reports of death occurring in dogs that have eaten a whole tub of cocoa powder.

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Symptoms of chocolate poisoning

Initially the dog will develop abdominal pain and vomiting which may contain blood. The dog may be restless, drooling saliva and could have difficulty standing or walking. Increased thirst is a very common problem. As the symptoms progress, in the more severely affected dogs, there is an increased rate of breathing, muscle tremors, or rigidity. Urine may contain blood and the colour of the gums may take on a bluish colour. Eventually the dog may develop convulsions and die.
In the majority of cases, the symptoms occur within a few hours, but it has been known to be delayed for as long as 24 hours. It can take as long as three days for the dog to recover completely. As well as the symptoms described above, there would also be an increase in heart rate with an abnormal rhythm.

How much is enough

If a dog consumes enough theobromine, the symptoms of poisoning will occur. The lethal dose of theobromine in dogs is between 250 and 500mgs/kg of dogs body weight (average: 300mgs/kg) . A good test of your own arithmetic skills is to calculate what dose would be lethal for you own dog! 

What may be lethal for one dog, may be no problem for another. Therefore some dogs will die well before the lethal dose has been reached and according to the Veterinary Poisons Information Service, 130mgs/kg was fatal to one dog. 

If we take a base and imagine a 20 kg dog ( about the size of most Collies), it may only require 130mg x 20 kgs body weight = 2600 mgs of theobromine to be a fatal dose. Dark chocolate as seen earlier has the highest theobromine content of eating chocolate ie 15mgs/gm chocolate. So dividing our 2600mgs lethal dose by 15 mgs results in a figure of about 170gms of dark chocolate as being lethal to a 20 kgs dog. That is about just a little bigger than your smallest slabs of chocolate. Remember the size of Easter eggs……..some can be very large, so death would be very common if a whole one is consumed.

The best advice is that if your dog has eaten any amount of chocolate or cocoa powders, then a visit to your vet is essential. DO NOT WAIT FOR SYMPTOMS TO APPEAR.

Treatment

Theobromine has no specific antidote. Chocolate poisoning is in every sense an emergency. Supportive treatment which could include sedation or even a general anaesthetic to stop fitting is all that can be done. If the dog is not fitting then more treatment options are available and the outlook is better. Most dogs presented to the vets due to chocolate poisoning usually all require a drip set-up, anti-nausea treatment ( to stop the vomiting) and an intestinal protectant to prevent further absorption of chocolate. This treatment would need to take place over a few days as chocolate is digested much slower in dogs than in man. 

Outlook of affected pets

The outlook very much depends on how much chocolate or cocoa powder the dog has eaten, and how long prior to being seen by the vet that the dog ate it. Unfortunately, most people are completely oblivious to the risks that chocolate poses, and delay until severe, persistent vomiting has developed before going to the vets. Once this stage has been reached, experience shows that up to 50% will die. 

Treated early enough, except for dogs that have consumed very large quantities of chocolate or cocoa powder, the outlook is generally good.

Recovered dogs show no long term ill effects from the poisoning.

Guy Liebenberg BSc BVSc MRCVS Cert Vet Acu

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