Chapter A1: Activated Charcoal

INTRODUCTION

Activated charcoal (AC) is an excellent nonspecific adsorbent. Conclusions regarding the role of AC in poison management are achieved through the integration of pharmacologic data, controlled volunteer trials, studies in heterogeneous patients with overdose or poisoning, and clinical experience. Activated charcoal is provided to a patient after a risk-to-benefit assessment of the presumed ingested xenobiotic and patient-specific factors and circumstances. Benefits include preventing absorption or enhancing elimination by blocking enterohepatic or enteroenteric recirculation of a potentially toxic xenobiotic; risks include vomiting and subsequent aspiration pneumonitis. A detailed discussion of the merits of AC as a decontamination strategy is presented in Chap. 5.

HISTORY

Charcoal a fine, black, odorless powder, has been recognized for more than two centuries as an effective adsorbent of many substances. Organic chemist Scheele first used charcoal to absorb gases in 1773 and was followed in 1791 by Lowitz’s use of charcoal with colored liquids.^6,89 Bertrand attributed his survival in 1811 from separate mercuric chloride and arsenic trioxide ingestions to their antecedent admixture with charcoal.¹¹⁹ In 1830, the French pharmacist Touery demonstrated the powerful adsorbent qualities of charcoal by ingesting several lethal doses of strychnine mixed with charcoal in front of colleagues, suffering no ill effects.⁶ An American physician, Holt, first used charcoal to “save” a patient from mercury bichloride poisoning in 1834.^6,89 However, it was not until the 1940s that Andersen began to systematically investigate the adsorbency of charcoal and unquestionably demonstrate that charcoal is an excellent, broad-spectrum gastrointestinal (GI) adsorbent.^6-8

PHARMACOLOGY

Chemistry and Preparation

Activated charcoal is produced in a two-step process, beginning with the pyrolysis of various carbonaceous materials such as wood, coconut, petroleum, or peat to produce charcoal. This processing is followed by treatment at high temperatures (600°–900°C) with a variety of oxidizing (activating) agents such as steam, carbon dioxide, or acids to increase adsorptive capacity through formation of an internal maze of pores.^30,60,121 Typical AC surface areas average 800 to 1,200 m²/g.¹¹⁷

Mechanism of Action

The actual adsorption of a xenobiotic by AC relies on hydrogen bonding, ion–ion, dipole, and van der Waals forces, suggesting that most xenobiotics are best adsorbed by AC in their dissolved, nonionized form.^{30,63,117,151}

Pharmacokinetics

Activated charcoal is pharmacologically inert and unabsorbed. Its GI transit time is influenced by the type and quantity and ingested xenobiotic, fasting and hydration status, perfusion, and the use of associated cathartics or evacuants, among other factors. The transit of AC is superimposed on a wide range of interindividual variation in gastric emptying and small bowel transit times, even in healthy volunteers.⁶² In six volunteers acting as their own controls, AC ...