The adsorptive capacity of charcoal has been documented since the time of Hippocrates and has been known for centuries. Two independent researchers were responsible for its wide acceptance in the early nineteenth century when each of them performed a demonstration of its effectiveness by ingesting lethal doses of strychnine and arsenic, respectively, followed by charcoal. Both of them survived. The twentieth century has seen charcoal come into wide medical use as further investigation showed its effectiveness at adsorbing a variety of compounds.1 Activated charcoal is currently the most commonly used mode of decontamination in the Emergency Department for poisoned patients.2
ANATOMY AND PATHOPHYSIOLOGY
Charcoal is produced by the distillation of the pyrolysis products of vegetable matter or wood. It works by directly adsorbing toxicants via a variety of chemical binding properties and preventing substances in the gastrointestinal tract from being absorbed into the circulation. Enhancement of the adsorptive capability of charcoal is achieved by heating it to a temperature of 900°C and then subjecting it to a stream of oxidizing gas (e.g., carbon dioxide or steam). This process is termed “activation” and creates an internal pore structure that increases the surface area from 2 to 4 square meters per gram to greater than 2000 square meters per gram (Figure 76-1).2 A typical dose of 50 gm of activated charcoal has the surface area of 10 football fields. Activated charcoal is not absorbed from the intestinal lumen nor is it modified by the numerous enzymes that aid in the digestion of food. It passes through the intestinal tract unchanged and is expelled as a sticky black substance.
Some activated charcoal preparations contain sorbitol. Sorbitol is used as a flavoring agent to make food, drinks, and medications more palatable. It is also used as a hyperosmotic laxative agent. It is poorly absorbed from the gastrointestinal tract and is converted into fructose by the liver. Its limited absorption results in an increased volume of water being secreted into the intestine causing an increased intraluminal pressure that stimulates catharsis.
Activated charcoal is usually used for decontamination, in single or multiple doses. Multiple doses of activated charcoal are considered in exposures to drugs with sustained- or delayed-release preparations or in situations where there is evidence of ongoing absorption. Multiple-dose activated charcoal can help enhance the elimination of certain compounds that exhibit enteroenteric or enterohepatic recirculation. A diffusion gradient is created in the intestine when multiple-dose activated charcoal is given for enhanced elimination due to the enormous adsorptive ability of charcoal to bind free toxicant. The intestinal mucosa functions as a semipermeable membrane, allowing absorbed drug or toxin to diffuse from the capillaries back into the lumen of the intestine. Activated charcoal can then adsorb and “trap” the toxin within the ...