What antibiotics are recommended for a 90-year-old female with suspected pyelonephritis, vomiting, and allergies to sulfa and penicillin, with impaired renal function (eGFR) and currently taking duloxetine?

Antibiotic Treatment for Pyelonephritis in a 90-Year-Old Female with Sulfa and Penicillin Allergies, Impaired Renal Function, and on Duloxetine

For a 90-year-old female with suspected pyelonephritis, active vomiting, sulfa and penicillin allergies, eGFR of 48, and on duloxetine, intravenous cefepime is the most appropriate initial treatment option, followed by oral levofloxacin once vomiting resolves.

Initial Assessment and Treatment Approach

• Active vomiting necessitates parenteral therapy as the patient cannot tolerate oral medications 1
• The patient's allergies to both sulfa and penicillin eliminate trimethoprim-sulfamethoxazole and penicillin-based antibiotics as treatment options 1
• Moderate renal impairment (eGFR 48) requires dose adjustment for many antibiotics 2
• Elderly patients with pyelonephritis require careful antibiotic selection due to increased risk of adverse effects 1

Recommended Antibiotic Regimen

Initial IV Therapy

• Cefepime IV is effective against common uropathogens and appropriate for patients with moderate renal impairment 1
• Dose adjustment required for eGFR 48: reduce standard dose by approximately 30-50% 2
• Avoid aminoglycosides as monotherapy due to high risk of nephrotoxicity, especially in elderly patients with already impaired renal function 1

Transition to Oral Therapy

• Once vomiting resolves, transition to levofloxacin 500 mg once daily (dose-adjusted for renal impairment) 1, 3
• Levofloxacin is preferred over ciprofloxacin in this patient due to:
  • Once-daily dosing improves compliance 1
  • Less drug interaction potential with duloxetine 3
  • Better coverage against common uropathogens in patients with renal impairment 3

Dosing Considerations for Renal Impairment

• For eGFR 48 ml/min/1.73m², reduce levofloxacin dose to 500 mg once daily (instead of 750 mg) 3
• Total treatment duration should be 10-14 days when using a fluoroquinolone in an elderly patient with pyelonephritis 1
• Monitor renal function during treatment as both the infection and antibiotics may affect kidney function 2

Important Clinical Considerations

• Obtain urine culture before initiating therapy to guide potential adjustments based on susceptibility results 1
• Monitor for QT prolongation with levofloxacin, especially in elderly patients and those on duloxetine 3, 4
• Assess for tendon disorders, which are more common in elderly patients on fluoroquinolones 4
• Consider drug interactions between fluoroquinolones and duloxetine, which may increase risk of CNS effects 5
• Monitor for signs of Clostridium difficile infection, which is more common with fluoroquinolones in elderly patients 6

Common Pitfalls to Avoid

• Using oral therapy initially in a patient with active vomiting 1, 7
• Prescribing aminoglycosides without careful monitoring in elderly patients with impaired renal function 2, 1
• Failing to adjust antibiotic doses based on renal function 2
• Not considering local resistance patterns when selecting empiric therapy 1
• Using nitrofurantoin for pyelonephritis, which is ineffective due to insufficient renal tissue penetration 1