In overdose and poisoning, when is activated charcoal most effective?

• A. It should be given within one hour of ingestion and is contraindicated in certain substances
• B. It is never effective
• C. It should be given only after emesis
• D. It is universally recommended for all poisonings

Answer: (A)

Activated charcoal works by adsorbing many toxins in the gut, so its benefit is greatest when given soon after ingestion. The practical window is about one hour, because as time passes the toxin moves beyond the stomach and the charcoal becomes less effective at preventing absorption. It’s not universally effective for all poisons—some substances bind poorly to charcoal (such as alcohols, hydrocarbons, and many metals), and others require different treatments. There are important contraindications too: if the airway can’t be protected, or if caustic or hydrocarbon substances were ingested because of aspiration risk, charcoal may be harmful or unnecessary. So the best description is that it should be given within one hour of ingestion and is contraindicated in certain substances.