Clinical Pharmacokinetics of Oral Activated Charcoal in Acute Intoxications

Abstract

Activated charcoal has the ability to adsorb a wide variety of substances onto its sUrface. This property can be applied in preventing the absorption of various drugs and toxins from the gastrointestinal tract and in some cases to increase their rate of elimination. In vitro. the extent of adsorption depends mainly on the relative amounts oj the charcoal and the drug ingested. but the quality and formulation of the activated charcoal. as well as other Jactors such as the pH of the incubation medium also have an effect. Under optimum conditions the adsorption to charcoal is a rapid process but desorption from charcoal is possible due. for example. to competition by other substances or to changes in pH.In acute poisonings the most important determinants of the efficacy oj activated charcoal are the delay in the administration and the amount of activated charcoal given. Activated charcoal should be given as a water suspension as soon as possible. preferably within 30 minutes oJthe ingestion of the toxic agent. However. in acute intoxications the absorption of drugs may be considerably delayed and thus charcoal may be effective when administered 24 hours after drug ingestion. At a constant charcoal-drug ratio. the adsorption capacity oj charcoal increases with increasing doses because the competitive effect of gastrointestinal contents diminishes. Thus the amount oj charcoal should be as high as feasible. i.e. about 50 to lOOg in adults. This amount is able to adsorb lethal doses of many drugs. Significant desorption from charcoal and subsequent systemic absorption of a drug is possible if inadequate amounts of charcoal are used. The adsorption to charcoal is more complete in poisonings with potent drugs. i.e. where the charcoal-drug ratio is high (e.g. digitalis glycosides. tricyclic antidepressants. etc.). With some drugs the adsorption capacity may be exceeded, e.g. in aspirin poisonings, but even in these cases the charcoal may adsorb that fraction oj the drug which is dissolved in the gastrointestinal./luids.In experimental studies. the efficacy of charcoal in preventing systemic absorption oj many drugs has been of the same order or even better than that of emesis, but in certain poisonings the efficacy oj charcoal is inadequate, e.g. in those caused by ethanol, methanol or iron salts. Charcoal is rather ineffective and may even be contraindicated in poisonings caused by caustic alkalis or acids. Charcoal is non-toxic but, if administered too rapidly, patients may vomit.Some drugs and toxic agents have a long elimination half-life and are excreted into the gastrointestinal tract and then reabsorbed. With such agents multiple oral doses of activated charcoal, e.g. 20g every 6 hours Jor 1 or 2 days, can accelerate their elimination and shorten the duration of intoxication.

Effect of charcoal‐drug ratio on antidotal efficacy of oral activated charcoal in man.

“…The direct application of these data to clinical toxicology is inappropriate and has led to the recommendation of extremely disparate amounts of the adsorbent during the past 10 years. The recommendations in the medical 770 K. T. Olkkola Charcoal-drug ratio and antidotal efficacy ofcharcoal literature have varied from 1 g to 120 g (Swinyard, 1970;Hayden & Comstock, 1975;Klaassen, 1980;Neuvonen, 1982).…”

Activated Charcoal as an Adjunct to Phototherapy for Neonatal Jaundice

“…However, charcoal has been reported to bind bilirubin in the gastrointestinal tract [Luecking and Kuenzer, 1966] and reduce plasma bilirubin levels in infants if treated during the first 4 h of life [Ulstrom and Eisenklam, 1964], The combina tion of charcoal and phototherapy has been reported [Hodr and Jirsova, 1980] to significantly accelerate the decrease of hyperbilirubinemia in infants when compared to phototherapy alone. Activated charcoal was used in this report because of its history [Federal Register, 1985;Neuvonen, 1982] of safe use in toxic emergencies and the need to further evaluate its effectiveness as an adsorbent of bilirubin.…”

Do gastric contents modify antidotal efficacy of oral activated charcoal?

“…Activated charcoal is a well known adsorbent whose ability to reduce the gastrointestinal absorption of different drugs has been shown in numerous studies as pointed out in some recent reviews (Hayden & Comstock, 1975;Neuvonen, 1982). The impairing effect of gastrointestinal contents on the adsorption capacity of activated charcoal has been known since the classical works of Andersen (1948).…”