Pharmacology · Specific antidotes
Activated charcoal !
A fine black powder that binds many poisons in the gut so less is absorbed. Most useful early after ingestion and only with a protected airway.
Updated 2026-11-01
Also called: Medicinal charcoal
Mechanism of action
Activated charcoal has an enormous porous surface that adsorbs many drugs and toxins inside the gastrointestinal tract, so they are not absorbed. Repeated doses also interrupt the enterohepatic recirculation of some drugs, pulling them back into the gut. It does not bind metals (iron, lithium, lead, mercury), alcohols or caustics.
- The poison is still in the stomach or gut
- Charcoal adsorbs it on its porous surface
- Less poison reaches the blood
- Repeated doses break enterohepatic recirculation
Pharmacokinetics
- Absorption
- Not absorbed: it works inside the gut lumen and leaves in the stool
- Onset and duration
- Most useful within the first hour after ingestion
Indications
- Recent ingestion of a toxic amount of a substance that charcoal adsorbs
- Repeated doses for drugs with enterohepatic recirculation, such as carbamazepine, phenobarbital, dapsone, quinine or theophylline
Adverse effects
Common
- Constipation
- Nausea and vomiting
- Black stools
Contraindications
- Depressed consciousness without a protected airway
- Substances it does not bind: metals (iron, lithium, lead, mercury), alcohols
- Caustics (it hides the mucosa at endoscopy) and hydrocarbons (aspiration risk)
- Bowel obstruction or risk of gastrointestinal bleeding or perforation
Key interactions
- Any oral medicine or oral antidote given at the same time
- It can be adsorbed too and lose its effect
What is monitored
- Level of consciousness and airway protection
- Bowel sounds and stools with repeated doses
- Signs of aspiration
Administration and safety
- Given by mouth or by nasogastric/orogastric tube as a slurry in water or saline, not distilled water
- Tube position is checked before each dose
- If the patient vomits, the dose is repeated slowly, sometimes with an antiemetic
- Before removing the tube it is aspirated, to reduce aspiration risk
Nursing care
- Check the time of ingestion and whether the substance is adsorbed
- Keep the head of the bed raised
- Watch for vomiting, abdominal distension and absent stools
- Tell the patient and family that stools will be black
Test yourself
Think of the answer, then tap the question to see it.
When is activated charcoal most useful?
Within about the first hour after ingesting a toxic amount of a substance it adsorbs, with a protected airway.
Which substances does charcoal not bind?
Iron, lithium and other metals (lead, mercury), alcohols such as methanol, caustics.
How do repeated doses help with drugs such as phenobarbital or carbamazepine?
They interrupt enterohepatic recirculation and keep pulling the drug back into the gut.
Related drugs
← Back to the class: Specific antidotes
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Guía para el Manejo de Emergencias Toxicológicas (Ministerio de Salud y Protección Social; Organización Panamericana de la Salud, 2017); eEML - Electronic Essential Medicines List (World Health Organization, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.