Acceleration of digoxin clearance by activated charcoal

Area of Science:

• Pharmacokinetics
• Toxicology
• Internal Medicine

Background:

• Digoxin is a cardiac glycoside with a narrow therapeutic index.
• Digoxin toxicity can lead to serious cardiac arrhythmias.
• Activated charcoal is known to bind to various substances in the gastrointestinal tract.

Purpose of the Study:

• To evaluate the effect of repeated oral doses of activated charcoal on the pharmacokinetics of intravenous digoxin.
• To determine if activated charcoal enhances digoxin elimination.

Main Methods:

• A randomized, crossover study involving ten healthy subjects.
• Subjects received intravenous digoxin alone and with repeated oral doses of activated charcoal (225 gm).
• Serum digoxin concentrations were measured over 40 hours using radioimmunoassay and analyzed with noncompartmental kinetics.

Main Results:

• Activated charcoal increased digoxin clearance by an average of 47% (12.2 to 18.0 L/hr).
• The volume of distribution decreased from 495 L to 375 L.
• The terminal half-life (t1/2) of digoxin was significantly shortened from 36.5 hr to 21.5 hr.

Conclusions:

• Repeated oral doses of activated charcoal enhance the elimination of intravenous digoxin.
• Activated charcoal administration effectively reduces digoxin's half-life and volume of distribution.
• Consideration should be given to using activated charcoal in managing digoxin toxicity, especially in patients with renal impairment.