How long has activated charcoal been used for medical purposes?

Poison ingestion
Activated charcoal is used to treat many types of oral poisonings such as phenobarbital and carbamazepine. It is not effective for a number of poisonings including: strong acids or bases, iron, lithium, arsenic, methanol, ethanol or ethylene glycol.

There are no randomized controlled trials that it improves outcomes and routine use is not recommended. In a study of acute poisonings from agricultural pesticides and yellow oleander seeds, the administration of activated carbon did not affect survival rates

Gastrointestinal tract-related issues
Charcoal biscuits were sold in England starting in the early 19th century, originally as remedy to flatulence and stomach trouble.

Tablets or capsules of activated carbon are used in many countries as an over-the-counter drug to treat diarrhea, indigestion, and flatulence. There is some evidence of its effectiveness to prevent diarrhea in cancer patients who have received irinotecan.It can interfere with the absorption of some medications, and lead to unreliable readings in medical tests such as the guaiac card test. Activated carbon is also used for bowel preparation by reducing intestinal gas content before abdominal radiography to visualize bile and pancreatic and renal stones. A type of charcoal biscuit has also been marketed as a pet care product.