Point of View: Activated Charcoal

November 1, 2010, 11:17 am

★★★★☆

Olson KR. Activated Charcoal for Acute Poisoning: One Toxicologist’s Journey. J Med Toxicol 2010;6:190-198.

Full Text

In this very interesting review/opinion piece, Kent Olson (from the California Poison Control System) describes how his thinking about the use of activated charcoal (AC) for gastrointestinal decontamination in acute poisoning has evolved.

When he started in toxicology in the early 1980s, Olson writes, the standard protocol required that all overdose patients had their stomachs emptied (by induced emesis or lavage) and were then administered AC.  But as the 80s progressed, studies began to question whether use of AC actually improved clinical outcomes, especially given the known risks (for example, aspiration).

Olson limns his purpose in this essay on the first page:

In this brief review, I will attempt to answer the following questions about activated charcoal: what is it and what does it bind to? What do animal studies and human volunteer studies reveal about its efficacy in simulated overdose? What evidence is there form case reports and controlled trials for its benefit in humans? What are the potential risks of administering activated charcoal? And finally, how can we put our knowledge about charcoal to use in managing specific patients?

In his discussion, Olson makes some provocative — if controversial — points:

• A recent meta-analysis of volunteer studies suggest that the optimal ratio of AC to toxin may be — not the usually cited 10:1 — but 40:1.

• Many studies claiming that some toxins (such as methanol or ethylene glycol) do not bind well to AC may just not have used enough charcoal. He quotes another author: “With almost any substance, if enough charcoal is given without undue delay, the charcoal will be reasonably effective in reducing the absorption of that substance.”

• We will probably never have sufficient evidence to know for sure in what situations the potential benefits of AC might outweigh its known risks.

Olson seems to agree with the criteria proposed by Greene (Pediatr Emerg Care 2008;24:176) for administration of oral AC: 1) potentially toxic ingestion; 2) no contraindications; 3) toxin is absorbed by AC; 4) toxin likely still in GI tract; 5) patient intubated or expected to maintain airway [note: this point is very important — the clinician should try to anticipate how the case will play out]; 6) GI tract functional and intact; 7) no better treatment (for example, an effective antidote such as N-acetylcysteine).

Potential toxins that are especially worrisome include cardiotoxic drugs (e.g., calcium channel blockers or chloroquine), cytotoxic agents (such as colchicine), and assorted nasties such as paraquat.

I don’t agree with all of Olson’s points.  For instance, he suggests that he would administer AC plus whole bowel irrigation (WBI) to a 16-year-old who ingested up to 28 venlafaxine SR and 28 zaleplon 45 minutes before presentation.  (He’s actually not quite clear on this point, or whether he would intubate before initiating these interventions.) To my knowledge, there is absolutely no literature showing that the combination of AC and WBI offers additional benefit over AC alone.

Neverless, this is a very informed and intelligent discussion of AC, and must-reading for toxicologists and other practitioners with a strong interested in the topic.

One Comment:

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