SIBO Treatment — SCE Palliative Medicine MCQ

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ModerateGI SymptomsSIBO TreatmentSCE Palliative Medicine

A 58‑year‑old woman with advanced ovarian cancer has developed small bowel bacterial overgrowth (SIBO) following multiple abdominal surgeries. She has bloating, diarrhoea, and malabsorption. What is the first‑line antibiotic treatment?

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Correct answer: D — Rifaximin 550 mg TDS for 14 days — a non‑absorbed antibiotic targeting gut bacteria with minimal systemic effects

Rifaximin is the optimal antibiotic for SIBO due to its minimal absorption and high luminal concentrations, with meta‑analysis showing approx. 70% eradication and low adverse events ([pubmed.ncbi.nlm.nih.gov](https://pubmed.ncbi.nlm.nih.gov/28078798/?utm_source=openai)). In UK NHS antimicrobial guidance, metronidazole is listed as first‑line primarily due to cost considerations, while rifaximin is acknowledged as evidence‑based when available ([elht.nhs.uk](https://elht.nhs.uk/download_file/1707/1777?utm_source=openai)). Ciprofloxacin and amoxicillin are systemically absorbed and less effective for luminal overgrowth. Vancomycin is reserved for Clostridioides difficile. Metronidazole is less effective than rifaximin and thus not preferred when rifaximin is accessible.

Reference: Gatta L, Scarpignato C. Systematic review with meta‑analysis: rifaximin is effective and safe for the treatment of small intestine bacterial overgrowth. Aliment Pharmacol Ther. 2017;45(5):604‑616. NHS Adult Antimicrobial Guide: Small Intestinal Bacterial Overgrowth. 2025 (approx). https://pubmed.ncbi.nlm.nih.gov/28078798/