Student Case Presentation
Udderly Septic: Altered Ampicillin Pharmacokinetics in a Critically Ill Calf
| Date/Time: |
8/27/2026 Poster 06
|
| Presenter: |
Haley Vaughan |
| Veterinary School: |
NC |
Abstract:
Sepsis is a life-threatening infection, typically bacterial in origin, that can lead to systemic inflammatory response syndrome (SIRS). SIRS is characterized by abnormalities in temperature, heart rate, respiratory rate, and leukocyte count due to release of inflammatory mediators, leading to severe organ dysfunction. SIRS is a major cause of illness and death in neonatal calves. Although antimicrobials are frequently used to treat calves with SIRS, limited research exists on pharmacokinetics in diseased animals. Diminished perfusion during sepsis can impair both drug clearance and distribution.
A 6-week-old miniature Jersey heifer presented for progressive weakness, hyporexia, and scours of two-week duration. Prior to presentation, the calf was managed with electrolytes and home remedies, followed by a three-day course of ampicillin and gentamicin. On presentation, the patient was laterally recumbent and minimally responsive. Physical examination findings included hypothermia, dehydration, increased bronchovesicular lung sounds, and injected scleras. Initial diagnostics revealed metabolic acidosis (< 6.80 mmHG), multiple electrolyte derangements, azotemia (creatinine 16.4 mg/dL, blood urea nitrogen 134 mg/dL), and band neutrophils (0.637 x 10^3/μL). Working diagnoses were chronic diarrhea of unknown etiology, acute kidney injury, and sepsis. Initial treatments included intravenous (IV) fluid therapy and IV ampicillin sodium 22 mg/kg every 6 hours. The patient was concurrently enrolled in a clinical research trial investigating ampicillin sodium pharmacokinetics in calves presenting with SIRS. Due to lack of improvement, the owner elected euthanasia the following day. Necropsy confirmed mycotic reticulorumenitis with secondary septicemia.
Pharmacokinetic data revealed prolonged drug exposure (AUC0-∞: 656.6 hr*μg/mL) and reduced clearance (CL: 1373.7 mL/hr) compared to other enrolled calves (AUC0-∞: 77.8 hr*μg/mL, CL: 11881.5 mL/hr). Clearance of ampicillin was likely reduced due to decreased renal function. These findings highlight the need for optimized dosing strategies in critically ill calves and suggest extended withdrawal times may be indicated in patients with compromised renal function.
