Activated charcoal is a fine, black, odourless and tasteless powder that is often used for emergency treatment of certain types of poisonings. It is not absorbed from the gastro-intestinal tract but has a local effect by adsorbing chemicals, drugs and bacterial toxins in the upper gastro-intestinal tract and thereby preventing or reducing their adsorption and preventing toxicity. Charcoal can also interrupt the enterohepatic circulation of a drug and increase diffusion of the chemical into the gastrointestinal tract. Many chemicals are however not adsorbed by charcoal including alcohols, hydrocarbons, metals, caustic alkalies, nitrates, sodium chloride/chlorate petroleum distillates and mineral acids. Although efficacy is not proven, activated charcoal is sometimes recommended to treat inorganic mercury poisoning. Administration with a cathartic, such as sorbitol, facilitates movement of the charcoal-toxins complex. The effectiveness of charcoal will depend on the time since the ingestion of the chemical or drug as well as on the dose of charcoal. Rapid administration of activated charcoal can induce emesis. Charcoal can also cause either constipation or diarrhoea and cause faeces to become black. Charcoal powder can stain fabric black and the dry powder tends to “hang” in the air covering wide areas. It can be prepared as a mixture of at least 50g in a glass of water and then be administered orally or via a gastric tube. Note that charcoal must never be administered with dairy products or mineral oil as this will reduce its efficacy. It must also not be administered with syrup of ipecac as the charcoal may adsorb the ipecac and reduce this drug’s emetic effect. Comparative volunteer studies have shown that activated charcoal is more effective than syrup of ipecac in decreasing drug adsorption.
REFERENCES: 1. Adams, HR (ed) 2001, ‘Veterinary pharmacology and therapeutics’, 8th ed., Iowa State University Press, Iowa, pp. 1056-1057. 2. Plumb, DC 2005, ‘Plumb’s veterinary drug handbook’, 5th ed. Blackwell Publishing, Iowa, pp.149-151. 3. Maddison, JE, Page, S.W. & Church D.B. (eds) 2008 ‘Small animal clinical pharmacology’, 2nd ed., Saunders Elsevier, Philadelphia, pp.489. 4. Brunton, LL, Lazo, JS & Parker, KL (eds) 2006, ‘Goodman & Gillman’s the pharmacological basis of therapeutics’, 11th ed., McGraw-Hill Medical Publishing Division, New York, pp.1748-1749, 1763. 5. Vale, JA & Proudfoot, AT 1993, ‘How useful is activated charcoal’, British Medical Journal, vol. 306, no. 6870, pp. 78-79. [http://0-www.bmj.com]
