Which drug should be avoided for chronic diarrhea because it can cause antibiotic-responsive enteropathy?

• A. Tylosin
• B. Amoxicillin
• C. Metronidazole
• D. Loperamide

Answer: (C)

Antibiotic-responsive enteropathy arises when chronic diarrhea is driven by an imbalance in the gut microbiota such that symptoms improve with antibiotic therapy. Some antibiotics can promote this pattern by profoundly altering intestinal bacteria, creating a state where diarrhea persists or recurs in a way that is most evident when antibiotics are used. Metronidazole, with its broad activity against anaerobes, can markedly shift the gut flora and contribute to this antibiotic-responsive phenotype, so it is best avoided as a chronic treatment when ARE is a concern. Using antibiotics for chronic diarrhea can tempt long-term reliance on antimicrobials and may mask underlying conditions, making metronidazole a less suitable choice in these scenarios.