Natural and synthetic adsorbents are prescribed as antidotes for the ingestion of toxins, substances that can lead to poisoning or overdose.
The most commonly used clinical adsorbent is activated charcoal, a black powder residue obtained from the distillation of various organic materials.
Activated charcoal must be administered soon after toxic inges-tion because it can bind only with drugs or poisons that haven’t yet been absorbed from the GI tract.
After initial absorption, some poisons move back into the in-testines, where they’re reabsorbed. Activated charcoal may be ad-ministered repeatedly to break this cycle.
Activated charcoal, which isn’t absorbed or metabolized by the body, is excreted unchanged in stool.
Because adsorbents attract and bind to toxins in the intestine, they inhibit toxins from being absorbed by the GI tract. However, this binding doesn’t change toxic effects caused by earlier absorp-tion of the poison.
Activated charcoal is a general-purpose antidote used for many types of acute oral poisoning. It isn’t indicated in acute poisoning from mineral acids, alkalines, cyanide, ethanol, methanol, iron,lithium, sodium chloride alkali, inorganic acids, or organic sol-vents. It also shouldn’t be used in a child who’s younger than age 1 year. In addition, it shouldn’t be used in a patient who has a risk of GI obstruction, perforation, or hemorrhage or decreased or ab-sent bowel sounds, or who has had recent GI surgery.
Activated charcoal can decrease absorption of oral medications; therefore, medications (other than those used to treat the ingested toxin) shouldn’t be taken orally within 2 hours of taking the acti-vated charcoal. The effectiveness of activated charcoal may be de-creased by vomiting induced by ipecac syrup. If both drugs are used to treat oral poisoning, activated charcoal should be used af-ter vomiting has ceased. (See Adverse reactions to activated char-coal.)