Activated charcoal is usually prescribed when your dog or cat has eaten something toxic. Being curious creatures our pets tend to explore everything in their environment. As they sniff, lick and nibble things sometimes they eat materials that are poisonous to them. Some food, plants, medications, cleaning products, batteries……nothing is safe. Although we try to be as vigilant as possible, this can happen too quickly to stop, when we are away from home or elsewhere in their territory. 

What is activated charcoal?

Carbon-containing compounds, usually as wood or wood and coal, are burned at very high temperatures to make activated charcoal. This charcoal has a very large surface area for its weight. One source states that 1g of activated charcoal has a surface area of 100 square metres. This huge surface means that activated charcoal is incredibly effective in absorbing gases and liquids. 

What does it do?

Any toxin that is eaten by your pet will be absorbed into the bloodstream from the stomach and intestines. When the toxin enters the bloodstream it will start to produce the symptoms of poisoning. These symptoms depend which toxin your pet has eaten. Some toxins cause gastrointestinal symptoms such as vomiting or diarrhoea. Others affect the nervous system causing weakness, tremor and seizures and others affect organs like the liver and kidneys. 

Activated charcoal is given by mouth so it enters the stomach and intestine and absorbs the toxin. This prevents it being absorbed into the bloodstream. In this way the symptoms of poisoning are prevented or reduced. Three doses are usually given 4-8 hours apart, the first may contain a laxative as well, to move the toxin through the intestine as quickly as possible. You may be given a powder or liquid. Both can be very messy as neither dogs nor cats are terribly keen to take this medication. A bib made from a towel for them and some old clothes for you can help reduce the mess. Charcoal can stain permanently so be careful.  

When should it be used?

The effects of activated charcoal are greatest when it is given as soon as possible after the toxin is eaten. It is most effective on an empty stomach. Your vet may have injected your pet to induce vomiting before the activated charcoal is given. This removes some of the toxin and stops any food material binding to the surface of the charcoal. The charcoal needs to be in physical contact with toxin to absorb it so food gets in the way.

A dose of 1-5g per kg is usually used for 3 doses. Sometimes it is used for longer if the toxin persists for longer. For example some medications are slow or sustained release and some can be reabsorbed after passing through the liver.

Activated charcoal is not an antidote to a particular toxin. Your pet may need other treatment as an antidote or to support their recovery. It is not effective for all toxins – e.g. it will not work for heavy metals such as Zinc or Iron. It does not absorb mineral oils, caustic or corrosive substances, salt or xylitol. The latter is a substance used in sugar free products and is often found in tasty treats such as peanut butter, sweets and chewing gum. 

It is effective for some medications and theobromines (in chocolate) are also bound by it. Activated charcoal can also be used as an absorbent in the treatment of flatulence and diarrhoea and sometimes for halitosis.  

Is it safe?

Activated charcoal is usually a safe and non-invasive treatment compared to flushing the stomach or the techniques used to limit toxins in people, like dialysis. However, there have been cases of its use worsening dehydration and causing high sodium levels. In a 2019 study by Mix, Stafford and Hofmeister, mild changes in sodium levels were seen in healthy dogs. This year there was also a case written up of obstruction of intestines by a charcoal impaction. 

As a result, activated charcoal should only be used under veterinary supervision

It can cause problems if your pet is dehydrated or has an injury to the stomach and intestinal wall. 

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Most pets will pass black faeces when treated, rarely they will show mild signs of gastrointestinal irritation like vomiting, diarrhoea or constipation. It is not safe to use activated charcoal if your animal has trouble swallowing, if they are continuing to vomit or are unconscious. It is a thick liquid or powder and can accidentally enter the lungs causing severe disease. In cases where further tests such as endoscopy are surgery are expected, charcoal can make interpreting the test difficult so it will not be used in these cases.

Other medications and nutrients given around the same time as activated charcoal will be bound by it and so be made ineffective, so it is wise to leave 2-3 hours between dosing other medications or feeding. Milk and liquid paraffin will make the charcoal less effective so shouldn’t be given at the same time. 

Activated charcoal can be a safe, effective treatment used as part of a protocol for managing many toxins in pets. But always use it strictly under veterinary guidance!