Systemic absorption from oral vancomycin: Check the dose!

Abstract

Background: Oral vancomycin is increasingly being used to treat Clostridium difficile infection. The extent of systemic absorption of oral vancomycin is unpredictable and usually minimal. However, in the presence of factors, such as renal impairment, or if high doses are used for prolonged periods, systemic absorption may occur, resulting in therapeutic levels of vancomycin. Aim: To describe a case of systemic absorption of oral vancomycin. Clinical details: A 69 year-old female with neutropenia and severe diarrhoea was admitted to the intensive care unit after an episode of hypotension due to hypovolaemia and septic shock. Fecal cultures were positive for C. difficile infection and she was started on oral vancomycin 500 mg 6-hourly. Serum creatinine at this time was 161 micromol/L. The clinical pharmacist identified the high dose of oral vancomycin being used and the potential problem with its absorption and recommended monitoring levels. After 7 days of treatment at this dose, the last 6 with normal creatinine, a spot level indicated a systemic vancomycin level of 5 mg/L. Outcome: On the return of a negative C. difficile culture, oral vancomycin was ceased after 9 days of treatment. Conclusion: The literature does not support oral vancomycin doses above 125 mg 6-hourly for the initial treatment of C. difficile-associated diarrhoea.