Activated Charcoal



30 Jan 2024 (Last Modified 06 Feb 2025)


Activated Charcoal

  1. Activated charcoal decreases absorption from the GI tract.
  2. Activated charcoal is the most commonly used method of GI decontamination.
  3. Activated charcoal can cause life-threatening inflammation of the lungs if it goes down the wrong tube.

The best treatment for a poisoning is to prevent it from happening. The next best treatment is to prevent your body from absorbing the poison. Activated charcoal is the most commonly used method of decreasing absorption from the gastrointestinal tract. It can only be safely used in patients who can swallow by themselves and is only effective for recently ingested solid poisons.

Activated charcoal decreases absorption from the GI tract.

Activated charcoal is a fine black powder made by burning materials that contain carbon and then heating the ash with gas to make it porous. These pores give activated charcoal a large surface area, which allows it to bind to a large amount of some other substance. 1 gram of activated charcoal has about the same surface area as a football field.

Activated charcoal binds to poisons in the GI tract, cloaking them, and carrying them out of the body. The body does not absorb activated charcoal. Activated charcoal only works for some solid poisons that are in stomach or first part of the small intestine. It does not work for:

  • Liquids or metals1
  • Poisons that have already been absorbed into the body2
  • Poisons that were inhaled or are on the skin.

The most effective dose of activated charcoal is 10 times the amount of poison ingested. It is difficult to calculate this dose in practice. We often do not know how much of the substance was ingested or how much remains in the stomach and adjacent parts of the small intestine3 and thus give 1 g/kg, which is about 50-100 g for an adult4. Despite different rates of digestion, activated charcoal seems to work as well in children as in adults.

Activated charcoal is usually given as a one-time dose. It can be given multiple times if the poison is one that recycles in the GI tract, a phenomenon called enterohepatic circulation, or if the absorption is prolonged. Giving mutiple doses of activated charcoal (MDAC) has been most studied in phenobarbital and aspirin overdoses, where it counteracts enterohepatic circulation and delayed absorption from pylorospasm, respectively.

Activated charcoal is most useful for recent ingestions of potentially lethal substances for which no antidote, like colchicine.

The theoretical rationale for giving activated charcoal is compelling but empiric evidence is lacking5. In a prospective trial, Merigian et al. (1990) found that activated charcoal did not improve outcomes. The trial studied patients who reported but had no symptoms and included patients who ingested liquids, which is not the population we would expect activated charcoal to help. The position of the American Academy of Clinical Toxicology is that activated charcoal should be given to patients who present within 1-2 hours of ingestion of a potentially lethal dose of a substance that is absorbed by activated charcoal (A.A. Of Clinical Toxicology,E.A. Of Poisons Centres,et al.,2005)6. I could not find a study that quantified the reduction in serum concentration of a substance as a function of the amount of activated charcoal given.

Activated charcoal is the most common method of GI decontamination.

Gastrointestinal decontamination refers to methods that prevent the GI tract from absorbing a substance. The main methods to decrease absorption from the GI tract are activated charcoal, gastric lavage7, and whole bowel irrigation.

Gastric lavage has fallen out of favor because it is not clear that gastric lavage is more effective than activated charcoal. Performing gastric lavage properly requires a sedated patient. Sedating may be dangerous, depending on the poison ingested. Complications of gastric lavage include perforating the esophagus, which can be fatal.

Whole bowel irrigation decreases absorption by decreasing transit time8. Whole bowel irrigation is useful for substances that are not absorbed by activated charcoal, like iron, lithium, and sustained-release drugs. It is also useful to clear the GI system of drug packets as can be found in body packers.

Ways not to prevent absorption.

  • Don’t induce vomiting. Although this might cause you to throw up some of the poison, it risks irritiating the esophagus. In some cases, such as people who ingested bleach, inducing vomiting may cause further injury. On the other hand, don’t try to prevent yourself from throwing up after ingestion. If you are awake and your body thinks you should throw up, let it.
  • Don’t “neutralize” the poison with milk. Unless you ingested acid, milk will have an unpredictable effect on the drug’s acidity. It, moreover, is not the case that poisons with a neutral pH are inactive. Most pills contain the active compound complexed with another ion to make it neutral8. Nor do all compounds share the same relationship between acidity and toxicity.

Activated charcoal can cause life-threatening inflammation of the lungs

The dogma in toxicology is that one should administer activated charcoal only to patients who can swallow by themselves. This is because activated charcoal can cause life-threatening inflammation of the lungs if it goes down the wrong tube. This makes common sense, even though scientific studies have not directly determined which patients are at risk for aspiration and at which doses of charcoal. Case reports from the 1980s and 90s document people aspiration after receiving activated charcoal. These cases do not directly apply to modern practice:

  1. There is bias towards publishing sensational cases. I did not include the case involving a French bulldog.
  2. The cases involved administering charcoal via nasogastric tube after gastric lavage.
  3. Some cases involved administering activated charcoal with sorbitol.
  4. Some cases described administering charcoal after ingesting a liquid poison.
  5. The drugs ingested have changed. All reports that described ingesting pills involved tricyclic antidepressants or baribiturates, which have largely been replaced by selective serotonin reuptake inhibitors and benzodiazepines, respectively.

Topics for Upcoming Podcasts.

  1. Can AC remove toxins from the blood?
  2. Can AC remove toxins already in body tissues?
  3. Multiple doses of AC.

Methods

To identify articles on aspiration pneumonitis after activated charcoal, I searched PubMed for “aspiration pneumonitis activated charcoal” and filtered for English-language case reports, case series, and clinical trials for which the full-text and abstract were available. Here is the link to the search results. Of the 12 articles identified, 5 described aspiration pneumonitis after a physician administered activated charcoal.

Reference Included? Notes
de Bairros et al. (2025) No Multiple medical interventions performed at home
Ayaz et al. (2021) Yes Administered via nasogastric tube
Caudill et al. (2019) No Case involved dog, not human
Moon, Chun, & Song (2015) No Retrospective observational study of activated charcoal and sorbital administered after liquid organophosphate ingestion
Seder et al. (2006) No Case involved activated charcoal accidentally directly instilled into lung
Hack, Gilliland, & Meggs (2006) No Only an image
Gutiérrez-Cı́a Isabel et al. (2006) No Behind paywall
Donoso et al. (2003) Yes Intubated, aspirated on extubation
Nogue et al. (2003) No Did not involve charcoal
(2002) No Case involved inadvertent administration into the trachea.
Vandenberg, Lutz, & Vinson (1999) No Involved oral suction from healthy volunteers
Harris & Filandrinos (1993) Yes Nasogastric tube dislodged, directly instilling charcoal into the trachea, developed ARDS, ultimately recovered
George, McLeod, & Weinstein (1991) Yes The patient aspirated tainted charcoal at home, fungi fed on the accompanying charcoal.
Elliott et al. (1989) Yes Aspiration from NG tube after gastric lavage.

References

  1. 1.Merigian, K. S. et al. Prospective evaluation of gastric emptying in the self-poisoned patient. The American journal of emergency medicine 8, 479–483 (1990).
  2. 2.Clinical Toxicology, A. A. of, Poisons Centres, E. A. of & Toxicologists, C. Position paper: single-dose activated charcoal. Clinical Toxicology 43, 61–87 (2005).
  3. 3.Bairros, A. V. de et al. Valproic acid intoxication–The importance of toxicological analysis and correct management: A case report. Toxicology Reports 14, 101891 (2025).
  4. 4.Ayaz, E. et al. Complicated pneumonia due to exogenous toxic substances in children. The Turkish Journal of Pediatrics 63, 149–154 (2021).
  5. 5.Caudill, M. N., Stilwell, J. M., Howerth, E. W. & Garner, B. Chronic granulomatous pneumonia and lung rupture secondary to aspiration of activated charcoal in a French Bulldog. Veterinary Clinical Pathology 48, 67–70 (2019).
  6. 6.Moon, J., Chun, B. & Song, K. An exploratory study; the therapeutic effects of premixed activated charcoal–sorbitol administration in patients poisoned with organophosphate pesticide. Clinical Toxicology 53, 119–126 (2015).
  7. 7.Seder, D. B., Christman, R. A., Quinn, M. O. & Knauft, M. E. A 45-year-old man with a lung mass and history of charcoal aspiration. Respiratory care 51, 1251–1254 (2006).
  8. 8.Hack, J. B., Gilliland, M. G. F. & Meggs, W. J. Images in emergency medicine-Activated charcol aspiration. Annals of Emergency Medicine vol. 48 522–+ (2006).
  9. 9.Gutiérrez-Cı́a Isabel, Obón-Azuara, B., Villanueva-Anadón, B. & Montoiro-Allué, R. Respiratory insufficiency due to accidental charcoal aspiration. Medicina Clinica 126, 598–598 (2006).
  10. 10.Donoso, A. et al. Activated charcoal laryngitis in an intubated patient. Pediatric emergency care 19, 420–421 (2003).
  11. 11.Nogue, S. et al. Fatal lipoid pneumonia due to bronco-aspiration of isoparaffin after ingestion of an organophosphate insecticide. Acta anaesthesiologica scandinavica 47, 777–779 (2003).
  12. 12.Chronic lung disease after activated charcoal aspiration. Pediatrics 109, 959–961 (2002).
  13. 13.Vandenberg, J. T., Lutz, R. H. & Vinson, D. R. Large-diameter suction system reduces oropharyngeal evacuation time. The Journal of emergency medicine 17, 941–944 (1999).
  14. 14.Harris, C. R. & Filandrinos, D. Accidental administration of activated charcoal into the lung: aspiration by proxy. Annals of emergency medicine 22, 1470–1473 (1993).
  15. 15.George, D. L., McLeod, R. & Weinstein, R. A. Contaminated commercial charcoal as a source of fungi in the respiratory tract. Infection Control & Hospital Epidemiology 12, 732–734 (1991).
  16. 16.Elliott, C. G., Colby, T. V., Kelly, T. M. & Hicks, H. G. Charcoal lung: bronchiolitis obliterans after aspiration of activated charcoal. Chest 96, 672–674 (1989).

Footnotes

  1. Activated charcoal does bind to thallium, as Hoffman et al. (1999) noted. Thallium is weakly electronegative. Th1+ has a lone pair in its valence shell. ↩

  2. It is unclear how long after an ingestion is too long to give activated charcoal. The rule of thumb of 1-2 hours assumes a person with no altered motility (e.g. no prior operations, no Crohn’s) who consumed a xenobiotic that does not alter motility (e.g. no opiates, no anticholinergics). ↩

  3. Most absorption of drugs occurs in the stomach and small intestine. ↩

  4. Activated charcoal seems to work as well in children as in adults. A direct comparison in a controlled study is unlikely to be performed. We cannot intentionally poison children. Children and adolescents tend to be poisoned from different substances than adults. ↩

  5. The lack of empiric evidence is ubiquitous in toxicology and arises from two main challenges. First, it is unethical to poison people to test treatments. This violates the ethical principal of equipoise. Second, a small fraction of the population take a potentially lethal doses of substances, with the exception of opioids and, increasingly, stimulants. Federal funding to study toxicity, lethal or otherwise, lags behind other conditions. By funding, I mean money for research and money for monitoring of products on the market. TODO: Importance of monitoring, use Boeing example. ↩

  6. The trick is to distinguish between an asymptomatic patient with impending toxicity and an asymptomatic patient who will stay asymptomatic. ↩

  7. Gastric lavage is also known as “pumping the stomach”. ↩

  8. Decreasing transit time is euphemistic. You drink the laxative used to prepare people for colonoscopies. Except you drink that entire amount every hour until “rectal effluent runs clear”. ↩ ↩2