Which of the following is a side effect of activated charcoal?

• A. Hypertension
• B. N/V, constipation, black tarry stools
• C. Diarrhea
• D. Rash and itching

Answer: (B)

Activated charcoal works by binding toxins in the GI tract, forming complexes that are eliminated in the stool. The most common adverse effects are gastrointestinal: it often causes nausea and vomiting, can lead to constipation, and the stool takes on a black color from the charcoal itself. Hypertension isn’t a typical side effect, diarrhea is less typical, and rash or itching would suggest an allergic reaction rather than a normal reaction to charcoal. So, nausea and vomiting, constipation, and black stools are the classic, expected side effects of activated charcoal.