A 4-year-old boy is brought to the emergency department after ingesting an unknown quantity of wild mushrooms picked from the backyard 10 hours ago. He has had several episodes of profuse, watery diarrhea and vomiting for the past 4 hours. Which of the following interventions, in addition to supportive care, is specifically recommended to block toxin binding and interrupt enterohepatic recirculation in this suspected poisoning?