Fiber Supplementation in Antibiotic‑Associated Diarrhea

Fiber Type Selection

• Soluble fibers such as psyllium/ispaghula husk or partially hydrolyzed guar gum (PHGG) are the most evidence‑supported options for patients with antibiotic‑associated diarrhea 1.
• Mixed soluble/insoluble fiber formulations also demonstrate efficacy, whereas insoluble fiber alone (e.g., wheat bran) may worsen symptoms and does not improve diarrhea outcomes [1][2].

Dosing and Administration

• Initiate supplementation with 4–8 g of soluble fiber taken three times daily, adjusting the dose according to tolerance [no citation – omitted].
• Provide 8–10 oz of fluid with each fiber dose to ensure adequate hydration [3][2].
• Continue the regimen for at least 2–5 weeks to achieve maximal microbiome restoration [no citation – omitted].

Expected Side Effects and Monitoring

• Flatulence is the most frequently reported adverse effect, but it is generally well tolerated in this patient group [3][2]4.

Contraindications and Cautions

• Avoid fiber supplementation in patients with intestinal strictures or obstruction, including those with stricturing inflammatory bowel disease [5][6].
• Do not start fiber in severely dehydrated patients until fluid status has been corrected 7.
• Fiber should not be used as sole therapy for Clostridioides difficile infection; appropriate anti‑C. difficile antibiotics (e.g., vancomycin or fidaxomicin) are required 8.

Complementary Therapies

• Probiotic adjuncts such as Lactobacillus rhamnosus GG or Saccharomyces boulardii (≥10 billion CFU/day) can be added to enhance treatment of antibiotic‑associated diarrhea [9][7].
• Prompt discontinuation of the inciting antibiotic, when clinically feasible, improves response to fiber therapy 8.
• Assess baseline dietary fiber intake before starting supplementation; patients with low habitual fiber intake derive the greatest benefit [3][2].

Mechanistic Benefits

• Fiber supplementation mitigates antibiotic‑induced gut dysbiosis by preserving anaerobic bacterial metabolism and preventing overgrowth of aerobic Proteobacteria, thereby addressing the underlying pathophysiology rather than merely slowing intestinal transit 7.
• By maintaining colonic short‑chain fatty‑acid production, fiber helps restore the microbial ecosystem disrupted by antibiotics 7.