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.)