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:
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.
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 entero-enteric 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.
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:
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 entero-enteric 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:
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.
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.
A position statement from the American Academy of Clinical Toxicology (AACT) in 2005 lists the following as contraindications and relative contraindications for AC use:
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.
As activated charcoal remains inert within the GI tract, no therapeutic index for systemic absorption exists.
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.
Activated charcoal is widely used in the emergency room to treat many types of toxicities. The agent is invaluable in preventing absorption of many toxic drugs and other poisons. Healthcare workers in the emergency room including nurses and physicians need to know when and how to use activated charcoal for the best results. The key feature about use of activated charcoal is that it must be used within 1-2 hours of the drug poisoning to be of benefit. While activated charcoal is widely sold in health food stores to treat a variety of other conditions, it is important to educate the patient about the harm of unregulated use of this substance.