What is the oral dose of Vancomycin for C. diff infection?

Oral Vancomycin Dosing for C. difficile Infection

For an initial episode of C. difficile infection, the recommended oral vancomycin dose is 125 mg four times daily for 10 days. 1

Dosing Based on Disease Severity

The appropriate dosing of oral vancomycin depends on the severity of C. difficile infection:

Non-severe CDI

• Vancomycin 125 mg orally four times daily for 10 days 1
• Alternative: Fidaxomicin 200 mg orally twice daily for 10 days 1

Severe CDI

• Vancomycin 125 mg orally four times daily for 10 days 1
• Alternative: Fidaxomicin 200 mg orally twice daily for 10 days 1

Fulminant CDI (previously called severe, complicated CDI)

• Vancomycin 500 mg orally four times daily 1
• If ileus is present: Add vancomycin 500 mg in 100 mL normal saline per rectum every 6 hours as a retention enema 1
• Plus intravenous metronidazole 500 mg every 8 hours, particularly if ileus is present 1

Clinical Severity Definitions

• Non-severe CDI: WBC ≤15,000 cells/mL and serum creatinine <1.5 mg/dL
• Severe CDI: WBC ≥15,000 cells/mL or serum creatinine >1.5 mg/dL
• Fulminant CDI: Hypotension, shock, ileus, or megacolon

Important Clinical Considerations

1. Dosing rationale: Although higher doses (500 mg four times daily) have been used, studies show that 125 mg four times daily achieves fecal concentrations 500-1000 times the MIC90 for C. difficile 1, 2. A study comparing high and low doses showed no significant difference in recurrence rates 3, 4.

2. First day considerations: Some patients with frequent stools may have lower fecal vancomycin levels during the first day of treatment 2. Consider a loading dose of 250 mg or 500 mg for the first 24-48 hours in patients with severe diarrhea.

3. Duration of therapy: Standard duration is 10 days 1. Some patients may require longer treatment courses.

4. Recurrent CDI: For first recurrence, options include:

   • Vancomycin 125 mg four times daily for 10 days (if metronidazole was used initially) 1
   • Tapered and pulsed vancomycin regimen (if standard regimen was used initially) 1
   • Fidaxomicin 200 mg twice daily for 10 days (if vancomycin was used initially) 1

5. Pediatric dosing: For children, the usual daily dosage is 40 mg/kg in 3-4 divided doses for 7-10 days, not to exceed 2 g daily 1, 5

Common Pitfalls to Avoid

1. Inadequate dosing: Using lower doses than recommended may lead to treatment failure, especially in severe cases.

2. Failure to adjust for severity: Not increasing the dose to 500 mg four times daily for fulminant CDI.

3. Inappropriate route: Oral vancomycin is not systemically absorbed and must be given orally for CDI. Parenteral vancomycin is ineffective for CDI 5.

4. Monitoring considerations: Patients with inflammatory bowel disorders or renal insufficiency may have significant systemic absorption of oral vancomycin and should be monitored for adverse effects 5.

5. Geriatric considerations: Patients >65 years should have renal function monitored during and after treatment due to increased risk of nephrotoxicity 5.

Oral vancomycin remains a cornerstone of CDI treatment with strong evidence supporting its use at appropriate doses based on disease severity.