Treating Toxins with Activated Charcoal in Dogs and Cats
The adsorptive properties of charcoal were first discovered some 300 years ago, with the first medicinal use of activated charcoal occurring in the 1800s. Nowadays, the administration of activated charcoal in suspected poisonings is commonplace along with gastric decontamination.
Since activated charcoal remains in the gastrointestinal tract (GIT), it is best to administer it when it’s believed the toxin is still present in the GIT. The exact timing depends on the toxin as well as the formulation and how much was ingested.
The adsorptive properties of activated charcoal come from its vast surface area and intermolecular forces. The ability of activated charcoal to absorb a toxin depends on several factors:
- particle size
- solubility
- ionization
- pH
Toxins that are in their nonionized form, non-polar, and poorly water-soluble are absorbed best. An insufficient dose of activated charcoal may also play a role in adsorption as there is a balance between the free toxin and how much toxin is bound to the activated charcoal. Acids, alkalis, alcohols, and metals such as lithium and iron do not bind well to activated charcoal and thus it is not recommended for these toxins.
Activated charcoal is generally safe to give, but because it is not risk-free it is best to give it when the benefits outweigh the risk of administration. There are a few times, besides charcoal being ineffective for the toxin, that activated charcoal should not be given:
- If the patient has an altered mental status or inability to protect their airway, activated charcoal should not be given due to the risk of aspiration.
- If the patient has altered electrolytes, particularly sodium, or is significantly dehydrated, activated charcoal should not be given due to the risk of worsening hypernatremia.
- If there is a concern for gastric perforation, it is best to avoid giving activated charcoal.
- If an endoscopy procedure may be necessary to retrieve something from the stomach, activated charcoal will limit visibility.
Backorders or unavailability of veterinary-activated charcoal products do happen occasionally. While human pharmaceutical activated charcoal may be used in animals, concentrations of products may differ from what is normally used. Therefore, it is best to check the concentration of charcoal for the product used and dose based on gram/kg instead of milliliters/kg.
Over-the-counter (OTC) activated charcoal capsules are available, but caution should be used before considering these products. In the US, they are considered supplements so oral efficacy and safety have not been evaluated. Furthermore, capsules typically contain 250 mg of charcoal, and thus doses often recommended on the label of 1-2 capsules are well below an appropriate dose for a toxicologic emergency. Caution is also advised to watch for homeopathic OTC products which may not have any activated charcoal present. Activated charcoal used in IV charcoal hemoperfusion machines has also not been tested for oral efficacy and safety.
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