Activated Charcoal

Overview

• Activated charcoal (AC), also known as activated carbon, is a highly porous form of carbon.
• It is thermally “activated” to create an extensive network of microscopic pores.
• Its primary purpose is to adsorb (bind) a wide range of substances in the gastrointestinal tract.
• This reduces their absorption into the body.

Benefits

• Acute Poisonings and Drug Overdoses: A single dose of 25–100 g of AC is a first-line decontamination agent.
  • It reduces systemic absorption of toxins like acetaminophen, tricyclic antidepressants, and certain pesticides.
• Gastrointestinal Support: 500–1000 mg of AC taken before a meal can bind gas-producing compounds.
  • Provides modest relief from bloating and flatulence, especially in patients with irritable-bowel-type symptoms.
• Cholesterol and Triglyceride Reduction: AC (500 mg twice daily for 4–12 weeks) may lower serum cholesterol and triglycerides.
  • Likely via adsorption of bile acids and dietary lipids.
• Anti-Inflammatory Effects: A 2-week regimen (500 mg twice daily) may reduce systemic inflammation markers (e.g., CRP) in healthy adults.
  • Larger, controlled trials are required.

How It Works

• High Surface Area: AC's efficacy derives from its high surface-area (≈500–1500 m² g⁻¹).
• Pore Structure: It has a predominance of sp²-hybridized carbon atoms arranged in aromatic rings, creating micro-, meso-, and macropores.
• Adsorption Process: These pores generate π-electron-rich surfaces that attract and bind (adsorb) polar and non-polar molecules.
  • This occurs through van-der-Waals forces, hydrogen bonding, and electrostatic interactions.
• Non-Covalent and Reversible Binding: Molecules such as toxins, drugs, and bile acids become trapped within the pores.
  • This prevents their passage across the intestinal epithelium.
• Bypassing Systemic Pathways: Because binding occurs in the lumen, systemic pharmacokinetic pathways (e.g., hepatic metabolism, renal excretion) are largely bypassed.
• Colonic Effects: AC may sequester microbial metabolites (e.g., endotoxin) and reduce gut-derived inflammatory signals in the colon.
  • This contributes to modest reductions in systemic inflammatory markers observed in short-term trials.

Dosage

• Acute Toxin Ingestion: The typical oral dose is 0.5–1 g kg⁻¹ (maximum 50 g) of powdered AC.
  • Administered as a single or repeated dose every 2–4 h for up to 3 doses, under medical supervision.
• Routine Gastrointestinal Support: Most commercial supplements recommend 300–600 mg taken 30 min before meals.
  • Maximum of 1 g per day.
• Cholesterol-Lowering or Anti-Inflammatory Applications: 500 mg taken twice daily with meals has been used in clinical studies lasting 4–12 weeks.
• Timing: AC should be taken at least 2 h before or after other medications or supplements.
  • Its non-selective adsorption can impair absorption.
• Patients with Dialysis or Chronic Kidney Disease: A lower dose (250 mg twice daily) is advised.
  • This is to avoid excess bowel loading.

Safety & Side Effects

• Common Side Effects: Generally well tolerated, but common side effects include black stools, constipation, and, rarely, gastrointestinal obstruction.
• Other Side Effects: Mild nausea and flatulence may occur with high-dose regimens.
• Contraindications:
  • Patients with compromised airways (risk of aspiration).
  • Severe gastrointestinal obstruction, perforation, or active bleeding.
• Drug Interactions: AC can significantly reduce the absorption of concurrently administered drugs.
  • A minimum 2-hour separation is recommended.
• Specific Conditions: Use should be limited in patients with chronic constipation or inflammatory bowel disease.
• Pregnancy and Lactation: Pregnant or lactating women should consult a clinician before use.
  • Data on fetal safety are limited.

Chemistry

• Composition: Activated charcoal is not a discrete molecule but a heterogeneous carbon matrix.
• Empirical Formula: Its empirical composition approximates C₁₀₀ (pure carbon).
• Structure: It has a highly irregular, amorphous structure lacking a definitive molecular formula or IUPAC name.
• Pore Structure: The material consists of fused aromatic rings (sp²-hybridized) arranged in a three-dimensional network with micro- (<2 nm), meso- (2–50 nm) and macropores (>50 nm).
• Activation Process: The high surface area arises from pyro-thermal treatment (800–1000 °C) and activation (steam or CO₂).
  • This generates abundant edge-plane sites and functional groups (hydroxyl, carbonyl, carboxyl).
• Activated State: The “activated” state refers to the presence of these surface functional groups and the extensive porosity.
  • This enables the adsorption of a broad spectrum of organic and inorganic substances.

Sources & Quality

• Feedstocks: Commercial activated charcoal is primarily derived from high-carbon feedstocks.
  • Examples include coconut shells, hardwood, or bamboo.
• Coconut Shell AC: Coconut-shell AC is favored for supplements.
  • It yields a high proportion of micropores and minimal ash content.
  • This enhances purity and adsorption capacity.
• Production Process: The process typically involves carbonization of the raw material.
  • This is followed by activation with steam or CO₂ at 800–1000 °C.
  • This develops the porous structure.
• Quality Control: Quality control includes measuring surface area (BET method), iodine and methylene-blue adsorption capacities, and microbial sterility.
• Pharmaceutical Grade: For pharmaceutical-grade AC, GMP-certified manufacturers must provide a certificate of analysis.
  • This confirms heavy-metal limits (<10 ppm lead, <5 ppm arsenic) and absence of microbial contamination.