Activated Charcoal

Article Author:
Jason Silberman
Article Editor:
Alan Taylor
Updated:
1/23/2018 12:31:35 PM
PubMed Link:
Activated Charcoal

Indications

An oral suspension of activated charcoal (AC) should be considered in poisonings when gastrointestinal decontamination of a xenobiotic is indicated, and AC can be administered within 1 hour of ingestion. Careful consideration of the contraindications (see below) should occur prior to treatment with activated charcoal.  

Observational trial data in recent years suggests AC should be given and may substantially reduce drug absorption and bioavailability in the following circumstances:

  • In anticipation of serious toxicity
  • Recent toxic ingestions. While the timeframe of less than 1 hour is classically described, AC administration may be beneficial if administered up to 4 hours after large ingestions and for the ingestion of substances with anticholinergic, or opioid properties that decrease intestinal motility
  • In alert and cooperative patients
  • When airway reflexes are intact, or the airway is protected by an endotracheal tube
  • Ingestions of xenobiotics without specific antidotes
  • When the ability to administer AC at AC: drug ratios is greater than 40:1. While an AC: drug ratio of 10:1 was previously thought to be ideal, recent studies suggest a ratio of 40:1 may be more beneficial. This ratio may be difficult to achieve in ingestions of a large drug mass at initial doses of AC are typically 25 to 100 g, and the risk of emesis increases as the amount of AC administered increases.
  • Ingestion of delayed release drugs. Single-dose activated charcoal (SDAC) may be efficacious outside of a 1-hour time frame when the systemic absorption of modified release substances is delayed.

Activated charcoal can be given for substances known to be adsorbed by activated charcoal (see below).

Multi-dose activated charcoal (MDAC) is often considered in cases of life-threatening ingestions of carbamazepine, dapsone, phenobarbital, quinine, and theophylline. Additional indications for possible MDAC therapy are listed below.

Mechanism of Action

Activated charcoal adsorbs xenobiotics within the gastrointestinal tract due to hydrogen bonding, ion-ion forces, and van der Waals forces. The AC/xenobiotic complex prevents systemic absorption of that xenobiotic. AC only adsorbs xenobiotics that are in the dissolved liquid phase via direct contact. Orally administered AC is not absorbed through the gastrointestinal lumen and acts within the gastrointestinal (GI) tract in its unchanged form.

Xenobiotics come in contact with AC if the drug has not yet been absorbed from the gastrointestinal lumen, or via recirculation of the xenobiotic into the gut lumen by either enterohepatic recirculation, or enteroenteric recirculation through active secretion, or passive diffusion.

Activated charcoal adsorption of xenobiotics is based on the equilibrium between the free xenobiotic and the AC/xenobiotic complex. Desorption of the xenobiotic from AC may occur. However, in the presence of adequate doses of activated charcoal, the equilibrium is shifted towards the AC/xenobiotic complex. This attempt to shift the equilibrium in favor of AC/xenobiotic complexes is the rationale for dosing activated charcoal to an AC: the xenobiotic ratio of 10:1 (see below).

AC best adsorbs xenobiotics in their nonionized forms. Polar, water-soluble molecules are less likely to be adsorbed. Due to the pharmacodynamics of AC, nonpolar, poorly water-soluble organic xenobiotics are best absorbed.

Most xenobiotics will have decreased systemic absorption in the presence of AC, including acetaminophen, aspirin, barbiturates, tricyclic antidepressants, theophylline, phenytoin, and a majority of inorganic and organic materials. It is important to note that AC does not effectively adsorb alcohols, metals such as iron and lithium, electrolytes such as magnesium, potassium, or sodium, and acids or alkalis due to the polarity of these substances.

Administration

AC should be administered when a xenobiotic is believed to still be in the gastrointestinal tract and when the benefits of preventing absorption of the xenobiotic are assumed to outweigh the risks of AC. Optimal dosing of AC is unknown. AC can be administered orally, or via nasogastric and orogastric tubes. When the dose of the xenobiotic is known, experts recommend AC at a 10:1 ratio of AC:xenobiotic. This may be impractical to achieve a 10:1 ratio when large doses (APAP or salicylates) are ingested. When the amount of xenobiotic ingested is unknown, or it is impractical to achieve a 10:1 ratio in large dose xenobiotic ingestions, SDAC should be administered in doses of 1g/kg of body weight.

SDAC can either be given as a 1 g/kg of body weight dose, or simplified age-based dosing below:

  • SDAC dosing adult: 25 to 100 g
  • SDAC dosing infants younger than 1 year: 10 to 25 g
  • SDAC children 2 to 12 years: 25 to 50 g
  • SDAC children older than 12 years: follow adult dosing

Multiple-dose activated charcoal (MDAC) is used when at least 2 sequential doses, and often several more, of activated charcoal, are given. MDAC is believed to prevent ongoing absorption of drug remaining within the GI tract and enhance elimination via enterohepatic or enteroenteric recirculation. While the quality of clinical data is not robust, MDAC is believed to be beneficial for “potentially life-threatening” ingestions of the following substances: carbamazepine, dapsone, phenobarbital, quinidine, theophylline, amitriptyline, dextropropoxyphene, digitoxin, digoxin, disopyramide, nadolol, phenylbutazone, phenytoin piroxicam, sotalol, amiodarone, dosulepin, duloxetine, lamotrigine, valproic acid, and verapamil.

Dosing strategies of MDAC vary. An initial dose of 10:1 ratio of AC: xenobiotic or 1 g/kg of bodyweight AC can be administered. It is best to tailor the dose and dosing intervals of MDAC to the amount and dosage form of xenobiotic ingested. Interval MDAC doses range from 0.25 to 0.5 g/kg of body weight every 1 to 6 hours in adults. AC has also been continuously administered through an NG tube in some cases.

 A simplified MDAC approach for adult patients would be:

  • Loading dose of 25 to 100 g
  • Repeat doses of 10 to 25 g AC every 2 to 4 hours

Due to the variability in proper dosing strategies and indications for MDAC administration, it would be a reasonable approach to consult a regional toxicologist, or Poison Control Center before the initiation of MDAC therapy.

Formulations have been attempted to increase the palatability of activated charcoal which comes in a black color and has a gritty texture. Ready-to-use aqueous suspensions of AC are available in 15 g, 25 g, and 50 g doses as well as formulations premixed with sorbitol. If AC is not premixed, a slurry can be made with AC in a 1:8 ratio of AC to a suitable liquid such as water, cola, or flavored syrups. Offering AC in an opaque cup with a lid and straw is an easy way to increase the palatability of AC.

Adverse Effects

As the dose of activated charcoal increases, the risk of adverse effects listed below increases.

An adequate airway assessment must take place before administration of activated charcoal. In patients with a depressed level of consciousness, providers must consider the risk-to-benefit ratio of intubation for airway protection and the therapeutic benefits of activated charcoal.

Aspiration pneumonitis can occur after emesis in patients with a depressed level of consciousness and in those who are fully alert with intact airway reflexes. Aspiration from emesis and misplaced nasogastric tubes for AC administration have led to severe respiratory compromise and even death.

Emesis occurs more often when AC is administered rapidly. The risk of emesis increases when sorbitol is added to AC.

Patients should be monitored for mental status changes and continued protection of their airway if emesis occurs. The provider should perform serial abdominal examinations to evaluate for signs of obstruction, or peritonitis, especially if MDAC is given.

Activated charcoal has listed drug interactions for leflunomide and teriflunomide as risk category D (consideration of therapy modification) due to decreased systemic absorption of these drugs.

Contraindications

A position statement from the American Academy of Clinical Toxicology (AACT) in 2005 lists the following as contraindications and relative contraindications for AC use:

  • Patients with an unprotected airway (in other words, a depressed level of consciousness) without endotracheal intubation
  • If AC use is likely to increase the risk and severity of aspiration of a xenobiotic (hydrocarbons with high aspiration potentials)
  • When the risk of GI perforation or hemorrhage is high secondary to medical conditions or recent surgery
  • When endoscopy is likely to be attempted as AC may obscure endoscopic visualization
  • In the presence of an intestinal obstruction
  • When AC is known to not meaningfully adsorb the ingested xenobiotic such as metals, acids, alkalis, electrolytes, or alcohols

MDAC is relatively contraindicated if decreased peristalsis is likely to occur from the substance ingested (opioids or anticholinergics). If MDAC is given to these patients, they should be monitored closely for development of obstruction, or potential aspiration.

Monitoring

As activated charcoal remains inert within the GI tract, no therapeutic index for systemic absorption exists.

Toxicity

No significant toxicity from activated charcoal exists as it is not systemically absorbed, however, adverse effects from the administration as listed above such as emesis, aspiration, and bowel obstruction requiring manual, or surgical decompression can occur.