Oral Vancomycin Dosing for Clostridioides difficile-Associated Diarrhea
For Clostridioides difficile-associated diarrhea (CDAD), the recommended dose of oral vancomycin is 125 mg administered four times daily for 10 days. 1
Treatment Based on Disease Severity
Non-Severe CDI
- Oral vancomycin 125 mg four times daily for 10 days 2, 1
- Alternatively, metronidazole 500 mg three times daily orally for 10-14 days may be used for mild-moderate cases 2
Severe CDI
- Oral vancomycin 125 mg four times daily for 10-14 days 2
- Despite some clinicians using higher doses (250-500 mg four times daily), studies have shown no significant difference in clinical outcomes between high-dose and low-dose vancomycin for severe CDI 3, 4
- The standard 125 mg dose yields fecal concentrations 500-1000 times the C. difficile MIC, making higher doses unnecessary in most cases 2
Fulminant CDI (with ileus or toxic megacolon)
- Oral vancomycin 500 mg four times daily 2
- Plus intravenous metronidazole 500 mg every 8 hours 2
- If ileus is present, add vancomycin 500 mg in 100 mL normal saline as retention enema every 6 hours 2, 5
Treatment for Recurrent CDI
First Recurrence
- Repeat the initial treatment regimen based on severity 2
Second or Subsequent Recurrences
- Vancomycin oral taper: 125 mg every 6 hours for 1-2 weeks, then 125 mg every 24 hours for 1 week, then 125 mg every 48 hours for 1 week 2
- Alternatively, fidaxomicin 200 mg twice daily for 10 days may be considered 2
- For multiple recurrences, consider fecal microbiota transplantation 2
Special Considerations
- Oral vancomycin is minimally absorbed, making it safe for most patients 1
- In patients with inflammatory bowel disorders or renal insufficiency, monitoring serum vancomycin levels may be appropriate due to potential increased systemic absorption 1
- Treatment response typically requires 3-5 days after starting therapy 2
- "Test of cure" is not recommended after CDI treatment 2
Common Pitfalls
- Using high-dose vancomycin (500 mg four times daily) for non-severe or severe CDI without ileus is unnecessary and increases cost without improving outcomes 3, 4, 6
- One study showed that patients may have lower fecal vancomycin levels during the first day of treatment with the 125 mg dose, suggesting a potential benefit of a loading dose of 250 mg or 500 mg during the first 24-48 hours in severe cases 7
- Parenteral administration of vancomycin is not effective for CDAD; vancomycin must be given orally or rectally (in cases of ileus) to reach the site of infection 1
- Antiperistaltic agents and opiates should be avoided as they may mask symptoms and worsen the disease 2
By following these evidence-based dosing recommendations, clinicians can effectively treat C. difficile infections while minimizing unnecessary high-dose therapy that increases costs without improving outcomes.