Table of Contents
This was first used in the 19th Century in France. Activated charcoal is made from material burnt in a super heated high oxygen atmosphere creating small holes in the range of 100 - 800 Angstroms in diameter throughout the grain of the charcoal. This effectively increases the charcoal's surface area so that the surface area of one gram of charcoal is approximately 1000 m2. Charcoal is effective in most self-poisonings with the exception of those drugs, which are poorly adsorbed by charcoal.
Most drugs are carbon based and have side chains that may adhere to carbon compounds by either chemical forces or weak electrostatic forces.
By supplying a large area of carbon surrounding the drug, the side chains are attracted to the carbon and the drug binds at a number of sites, effectively sticking to the charcoal.
It is a dynamic interaction and the drug may leave the initial binding site and either re-bind or be absorbed. For this reason, cathartics have been administered to shorten GI transit time. However, there is no demonstrated advantage in giving activated charcoal with sorbitol, compared with water, other than slight improvement in palatability.
INDICATIONS FOR CHARCOAL
Activated charcoal is indicated for most if not all poisonings that fulfill the following criteria:
- Drug ingested is adsorbed by charcoal and has significant potential for toxicity
- Time since ingestion is less than 1-2 hours
- The drug has significant enterohepatic circulation
- The drug delays gastric emptying and time since ingestion is less than 4 hours
- The drug is in a controlled release preparation and time since ingestion is less than 12-18 hours
DOSE OF CHARCOAL
In the test tube, there are optimal ratios of charcoal to different drugs to get complete adsorption. In clinical practice, very large doses are needed and it is commonly recommended to give 1g/kg of body weight.
This is currently administered in a premixed solution generally mixed with sorbitol or water. We no longer recommended sorbitol, which is an osmotic cathartic. The sorbitol causes fluid to shift into the bowel leading to diarrhoea and a (theoretically) more rapid transit time for the charcoal and charcoal drug complex. Consequently, patients require additional fluids, either intravenous or oral.
There is no demonstrated advantage in giving activated charcoal with sorbitol, compared with water, other than slight improvement in palatability. The sorbitol may also be responsible for some of the complications.
In most patients, charcoal and water should be administered if charcoal is indicated.
The dose should be 1 gram per kg of body weight.
ADMINISTRATION OF CHARCOAL
It is not necessary for charcoal to be administered by a nasogastric or orogastric tube. However, after gastric lavage, charcoal is normally put down the tube prior to removal. The oral acceptance of charcoal is high when administered in the appropriate circumstances. The oral acceptance is increased if the activated charcoal is chilled.
In children the administration in a covered container or mixed with fruit juice, yogurt or ice-cream has been shown to increase acceptance (but may decrease efficacy).
In adult patients it is particularly important to set a clear goal, generally that the patient should drink 50 g of charcoal within 20 minutes. It should be made clear to the patient that if they can't drink the charcoal in the stated time or do not feel they can drink it at the outset, then a nasogastric tube can be inserted to administer the charcoal. In this situation it often needs to be further diluted in order to flow down the tube.
If you are not prepared to proceed with nasogastric tube insertion to ensure charcoal administration you should be thinking seriously about whether charcoal is needed or not.
COMPLICATIONS OF CHARCOAL
- Aspiration of charcoal and cathartic: in this situation it is probably the hyperosmolar cathartic that is responsible for the development of non cardiogenic pulmonary oedema.
- Bowel obstruction may occur when activated charcoal is given without cathartics.
- Hypotension/tachycardia may occur due to hypovolaemia. This develops as the osmotic cathartic causes fluid to shift into the bowel.
Palatnick W, Tenenbein M. Activated charcoal in the treatment of drug overdose. An update. Drug Safety 1992;7:3-7.
Bradberry SM, Vale JA. Multiple-dose activated charcoal: a review of relevant clinical studies. Journal of Toxicology - Clinical Toxicology 1995;33:407-416.
Chyka PA, Seger D. Position statement: single-dose activated charcoal. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists. J Toxicol Clin Toxicol 1997; 35(7):721-741.
Position statement and practice guidelines on the use of multi-dose activated charcoal in the treatment of acute poisoning. American Academy of Clinical Toxicology, European Association of Poisons Centres and Clinical Toxicologists. J Toxicol Clin Toxicol 1999; 37(6):731-751.
Bond GR. The role of activated charcoal and gastric emptying in gastrointestinal decontamination: a state-of-the-art review. Ann Emerg Med 2002; 39(3):273-286.