Introduction
Activated charcoal is a black odorless powder made from carbon based substances such as wood, peat, coconut, or petroleum. Processing with heat and oxidizing agents “activates” the charcoal into a highly porous powder with a very large surface area (800-1,200 m2/g of powder).1 This high amount of surface area allows activated charcoal to non-specifically bind drugs and toxins in the gastrointestinal tract, preventing their absorption. While other methods of gastric decontamination such as syrup of ipecac or gastric lavage have largely fallen out of favor, activated charcoal remains an important tool in managing poisoned patients.
Gastric Decontamination
The primary use of activated charcoal is to decrease the absorption of an ingested drug or poison. Both volunteer studies and studies in overdose patients have demonstrated decreased absorption of drugs when charcoal is administered within a reasonable time.2,3 Decreased need for treatment has also been shown, such as with n-acetylcysteine for acetaminophen overdoses treated with charcoal.4 One hour post-ingestion is often used as a cutoff for charcoal administration. However, many overdoses may benefit from charcoal administration well beyond 1 hour.5 These include the ingestion of extended-release formulations or drugs that form bezoars, as well as very large ingestions. The dose for gastrointestinal decontamination is 50-100 g for adults and 1 gm/kg or 10-25 g in children.6 This dose may be repeated following a large ingestion or if the ingested substance is absorbed slowly, such as in many aspirin overdoses.
Enhancing Elimination
Activated charcoal has also been shown to increase the rate of elimination of certain drugs after they have been absorbed into the body. This can occur because some drugs are excreted from the body into the gastrointestinal tract and reabsorbed. Repeat doses of activated charcoal can bind excreted drug and interrupt this hepatoenteric or enteroenteric recirculation. This ability to increase the rate of a drug’s elimination is separate from charcoal’s ability to prevent absorption, and is not limited by a post-ingestion timeframe. Carbamazepine, phenytoin, and phenobarbital are examples of drugs that have shown shorter half-lives when treated with repeat-dose activated charcoal.7,8,9 The dose for enhanced elimination is 15-30 g every 2-4 hours.6
Limitations and Adverse Effects
While most substances bind well by charcoal, some drugs and other toxins are not well adsorbed. Examples of these include iron, lithium, potassium, and fluoride.6 Charcoal will not prevent damage from the ingestion of strong acids or alkalis, and can also complicate endoscopy findings after the ingestion of these caustic substances.
There is a risk of vomiting and aspiration of charcoal and other stomach contents.10 Because of this, charcoal should not be given to a drowsy patient or patient that may become rapidly drowsy following an ingestion. In a patient requiring intubation, charcoal may be given via a gastric tube once a patient’s airway is protected. In overdoses with no more than mild effects expected, the risk of vomiting and aspiration often outweighs the limited benefit of charcoal in such scenarios.
Formulations
Activated charcoal is available for oral suspension alone and with sorbitol added as a cathartic. Abdominal pain, vomiting, and excessive diarrhea are possible with sorbitol. Because of this, formulations with sorbitol should not be used when multiple doses of charcoal are planned, especially in young children and elderly patients due to the risk of dehydration and electrolyte abnormalities.11 Charcoal is also available in capsule form from health food stores, online, and pharmacies, and is intended to relieve cramping, bloating, and indigestion. The dose in these capsules (measured in milligrams) is well below the clinically used doses in poisonings (measured in grams), and home use of charcoal is not recommended for poisoning exposures.
Summary
Charcoal is an easy and non-invasive treatment that can be applied to a wide variety of poisonings. It can be used for both gastrointestinal decontamination as well as enhanced elimination. Contact the Utah Poison Control Center with questions concerning charcoal use.
References
- Olson KR. Activated charcoal for acute poisoning: one toxicologist’s journey. J Med Toxicol. 2010;6:190–198.
- Wananukul W, et al. Effect of activated charcoal in reducing paracetamol absorption at a supra-therapeutic dose. J Med Assoc Thai. 2010;93:1145–1149.
- Van Gorp F, et al. Population pharmacokinetics and pharmacodynamics of escitalopram in overdose and the effect of activated charcoal. Br J Clin Pharmacol. 2012;73:402–410.
- Buckley NA, Whyte IM, O'Connell DL, Dawson AH. Activated charcoal reduces the need for N-acetylcysteine treatment after acetaminophen (paracetamol) overdose. J Toxicol Clin Toxicol.
- Hoegberg LCG, Shepherd G, Wood DM, et al. Systematic review on the use of activated charcoal for gastrointestinal decontamination following acute oral overdose. Clin Toxicol (Phila). 2021;59(12):1196-1227.
- Olson KR, Anderson IB, Benowitz NL, et al. Poisoning & Drug Overdose. New York: McGraw Hill Education; 2018.
- Wason S, et al. Carbamazepine overdose—the effects of multiple dose activated charcoal. J Toxicol Clin Toxicol. 1992;30:39–48.
- Skinner CG, et al. Randomized controlled study on the use of multiple-dose activated charcoal in patients with supratherapeutic phenytoin levels. Clin Toxicol (Phila). 2012;50:764–769.
- Pond SM, et al. Randomized study of the treatment of phenobarbital overdose with repeated doses of activated charcoal. JAMA. 1984;251:3104–3108.
- De Weerdt A, et al. Rapid-onset adult respiratory distress syndrome after activated charcoal aspiration. A pitch-black tale of a potential to kill. Am J Respir Crit Care Med. 2015;191:344–345.
- Farley TA. Severe hypernatremic dehydration after use of an activated charcoal-sorbitol suspension. J Pediatr. 1986;109:719–722.