Systemic absorption of oral vancomycin in patients with Clostridium difficile infection.

Oral vancomycin is utilized in the treatment of severe Clostridium difficile infection (CDI). We prospectively measured serum vancomycin concentrations (SVC) in patients treated with oral vancomycin. The SVC was measured by immunoassay prior to, and at least 3 days after, the administration of oral vancomycin 125 mg every 6 h. Patients treated with intravenous vancomycin were excluded. Fifty-seven patients with a mean age of 74 y (± 18) were enrolled. There was no detectable SVC in 56 patients (98%); 1 patient had a transient SVC of 6.7 μg/ml that was not detectable on subsequent testing. The severity of the CDI and/or renal failure did not have an effect on SVC. Orally administered vancomycin at 125 mg 4 times daily was not absorbed from the gastrointestinal tract.