An oral suspension of activated charcoal (AC) should merit consideration in poisonings when there is an indication for gastrointestinal decontamination of a xenobiotic, and the clinician can administer activated charcoal within 1 hour of ingestion. Careful consideration of the contraindications (see below) should take place before treatment with activated charcoal.
Observational trial data in recent years suggests activated charcoal should be given and may substantially reduce drug absorption and bioavailability in the following circumstances:
Activated charcoal is an option for substances known to be adsorbed by activated charcoal (see below).
Multi-dose activated charcoal (MDAC) is often a consideration 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 activated charcoal/xenobiotic complex prevents systemic absorption of that xenobiotic. Activated charcoal only adsorbs xenobiotics that are in the dissolved liquid phase via direct contact. Orally administered activated charcoal does not get absorbed through the gastrointestinal lumen and acts within the gastrointestinal (GI) tract in its unchanged form.
Xenobiotics come in contact with activated charcoal 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 activated charcoal/xenobiotic complex. Desorption of the xenobiotic from activated charcoal may occur. However, in the presence of adequate doses of activated charcoal, the equilibrium is shifted towards the activated charcoal/xenobiotic complex. This attempt to shift the equilibrium in favor of activated charcoal/xenobiotic complexes is the rationale for dosing activated charcoal to activated charcoal: the xenobiotic ratio of 10 to 1 (see below).
Activated charcoal best adsorbs xenobiotics in their nonionized forms. Polar, water-soluble molecules are less likely to be adsorbed. Due to the pharmacodynamics of activated charcoal, it best absorbs nonpolar, poorly water-soluble organic xenobiotics.
Most xenobiotics will have decreased systemic absorption in the presence of activated charcoal, including acetaminophen, aspirin, barbiturates, tricyclic antidepressants, theophylline, phenytoin, and a majority of inorganic and organic materials. It is important to note that activated charcoal 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.
The clinician should administer activated charcoal when they believe a xenobiotic is still in the gastrointestinal tract, and when the benefits of preventing the absorption of the xenobiotic are assumed to outweigh the risks of activated charcoal. The optimal dosing of activated charcoal is unknown. Activated charcoal administration can be oral, or via nasogastric and orogastric tubes. When the dose of the xenobiotic is known, experts recommend activated charcoal at a 10 to 1 ratio of activated charcoal to xenobiotic. This ratio may be impractical to achieve when the patient has ingested large doses (APAP or salicylates). When the amount of xenobiotic ingested is unknown, or it is impractical to achieve a 10 to 1 ratio in large dose xenobiotic ingestions, SDAC should administration should be in doses of 1g/kg of body weight.
SDAC administration can either be as a 1 g/kg of body weight dose or simplified age-based dosing below:
Multiple-dose activated charcoal (MDAC) is when at least two sequential doses, and often several more, of activated charcoal, are given. MDAC appears 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, Researchers believe MDAC is 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. As mentioned already, initial dosing is either a 10 to 1 ratio of activated charcoal to xenobiotic or 1 g/kg of bodyweight activated charcoal; both are options. 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. Some cases have employed the continuous administration of activated charcoal 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 is black and has a gritty texture. Ready-to-use aqueous suspensions of activated charcoal are available in 15 g, 25 g, and 50 g doses as well, as formulations premixed with sorbitol. If activated charcoal is not premixed, a slurry can be made with activated charcoal in a 1 to 8 ratio of activated charcoal to a suitable liquid such as water, cola, or flavored syrups. Offering activated charcoal in an opaque cup with a lid and straw is an easy way to increase the palatability of activated charcoal.
As the dose of activated charcoal increases, the risk of adverse effects listed below increases.
An adequate airway assessment must take place before the 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 activated charcoal administration have led to severe respiratory compromise and even death.
Emesis occurs more often with rapid administration of activated charcoal — the risk of emesis increases when the activated charcoal has sorbitol added.
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 giving MDAC.
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 activated charcoal use:
MDAC is relatively contraindicated if decreased peristalsis is likely to occur from the substance ingested (opioids or anticholinergics). If these patients receive MDAC, they should be monitored closely for the 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 the 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 critical feature in the use of activated charcoal is that it generally must be used within 1 to 2 hours of 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 the unregulated use of this substance.
A clinician contemplating the use of activated charcoal would do well to consult a clinical pharmacist or toxicologist if there are any doubts regarding the appropriateness of its use. These resources can also assist with appropriate dosing and administration. Nursing will administer the activated charcoal, and should monitor the patient to watch for adverse events as well as assess the effectiveness of the intervention. Functioning as a collaborative interprofessional team will optimize patient outcomes when using activated charcoal for toxic ingestions. [Level V]
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