Abstract: TH-PO0846
When "Safe" Isn't Safe: Clinically Significant Systemic Vancomycin Exposure from Oral Therapy in a High-Risk Patient
Session Information
- Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
October 22, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
- 1900 Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
Authors
- Agosto, Jennifer, University of Florida College of Medicine - Jacksonville, Jacksonville, Florida, United States
- Rios Leite, Daniele, University of Florida College of Medicine - Jacksonville, Jacksonville, Florida, United States
- Hasan, Irtiza, University of Florida College of Medicine - Jacksonville, Jacksonville, Florida, United States
Introduction
Oral vancomycin is widely considered minimally absorbed and therefore safe from systemic toxicity. However, emerging evidence suggests meaningful absorption with clinically significant levels may occur in high-risk populations, particularly in the presence of severe mucosal inflammation and renal dysfunction. We present a case highlighting the potential significance of detectable vancomycin levels following oral administration even when not traditionally considered toxic.
Case Description
A 58-year-old female presented with foul-smelling diarrhea, sepsis and was diagnosed with severe Clostridioides difficile colitis. Past medical history included active breast cancer on chemotherapy, past C. difficile colitis and hypertension. Her course was complicated by hypotension, acute-on-chronic anemia requiring transfusion, contrast exposure and acute kidney injury. On admission, serum creatinine was 1.2 mg/dL (baseline 0.5–0.7 mg/dL). CT imaging revealed severe pancolitis. She was started on oral vancomycin (500 mg/day). Despite volume optimization, renal function worsened with declining urine output. Urinalysis showed granular casts, consistent with intrinsic kidney injury. A random vancomycin level obtained on hospital day 8 was 14.7 µg/mL, rising to 17.6 µg/mL the following day and vancomycin was stopped. Although these levels are below typical thresholds associated with toxicity in intravenous therapy, they indicated significant systemic absorption. By hospital day 15, serum creatinine peaked at 8.14 mg/dL. The patient required initiation of hemodialysis on hospital day 16 and remained dialysis-dependent for approximately one month before renal recovery.
Discussion
This case demonstrates that oral vancomycin can result in clinically meaningful systemic exposure in high-risk patients, particularly those with severe colitis, disrupted mucosal integrity, and evolving renal dysfunction. Importantly, even moderate serum levels below traditional toxicity thresholds may still be clinically relevant in vulnerable populations. Current guidance suggests considering monitoring in such settings; however, this practice is not standardized. Oral vancomycin should not be universally assumed to be non-systemic, and a lower threshold for monitoring vancomycin levels and renal function may be warranted in selected high-risk patients.