Levofloxacin Ordered for Inpatient Pneumonia in a Patient With Prior Tendon Rupture, AAA and a High INR
Mr. B., 67, is admitted to the medical ward with a 3-day history of productive cough, fever 38.6 °C and dyspnea. Chest X-ray shows right lower lobe consolidation; CURB-65 score is 1. The resident writes levofloxacin 750 mg IV q24h and asks you to 'just check the dose' before the first dose is given. Chart: CrCl 48 mL/min (CKD 3a), warfarin 5 mg daily with INR 3.4 today (target 2.0–3.0), prednisone 10 mg daily, amlodipine 5 mg daily, metformin 500 mg BID. Allergy: sulfa (rash). History: Achilles tendon rupture in 2019, abdominal aortic aneurysm 4.2 cm under surveillance, type 2 diabetes, QTc 452 ms on today's ECG. He is hemodynamically stable, saturating 94% on 2 L nasal prongs. The resident is paged to an emergency and will not return for at least an hour.
1. Beyond checking the renal dose, what problems do you see with this order?
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The renal dose is only the first problem.
- Wrong interval. For CrCl 20–49 mL/min, levofloxacin 750 mg should be given every 48 hours (or 500 mg every 24 h). The order is q24h - an overdose in renal impairment.
- Tendinopathy risk. Prior Achilles tendon rupture plus concurrent prednisone is a strong reason to avoid fluoroquinolones; recurrent rupture and bilateral tendinopathy are recognized.
- Aortic aneurysm. Health Canada has warned that fluoroquinolones may increase the risk of aortic aneurysm and dissection; he has a 4.2 cm AAA under surveillance.
- Warfarin. Levofloxacin potentiates warfarin and his INR is already 3.4 (above target). He is at bleeding risk.
- QTc 452 ms. Fluoroquinolones prolong QT; avoid combining with other QT-prolonging drugs.
- Dysglycemia. Fluoroquinolones can cause hypoglycemia, relevant in a patient with diabetes.
- Sulfa allergy is irrelevant to levofloxacin, but it is a reminder to verify the allergy list.
Immediate action: do not give the first dose; page or call the prescriber and document; if the prescriber cannot be reached, follow the hospital's antimicrobial stewardship or pharmacist-initiated substitution policy.
2. Recommend an alternative empiric regimen for this admission and justify it, including renal adjustments.
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Recommended regimen (inpatient, non-ICU CAP, CURB-65 = 1): ceftriaxone 1–2 g IV q24h plus azithromycin 500 mg IV/PO q24h. This is consistent with Canadian CAP guidance for hospitalized patients and avoids the fluoroquinolone toxicities above.
- Renal dosing: ceftriaxone needs no adjustment at CrCl 48 (it is cleared by both renal and biliary routes). Azithromycin needs no adjustment.
- Allergy: his only allergy is sulfa (rash); cephalosporins are acceptable.
- Alternative if beta-lactam intolerance: ceftriaxone can be replaced with doxycycline 100 mg BID plus azithromycin, or with a respiratory fluoroquinolone only if there is no other option - not appropriate here.
- Duration: 5–7 days if clinically stable and afebrile, per current guidance.
- MRSA/Pseudomonas: no risk factors documented, so no broadened coverage.
Justification to the resident: 'CrCl is 48, so levofloxacin 750 mg q24h is an overdose; plus prior tendon rupture, AAA, INR 3.4 and QTc 452 make a fluoroquinolone a poor choice. Ceftriaxone plus azithromycin covers the likely pathogens without those risks.'
3. Outline your monitoring plan and the counseling you would give this patient.
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Monitoring:
- INR daily for the first 2–3 days, then every 2–3 days; any antibiotic can disturb gut flora and warfarin effect. Expect to reduce the warfarin dose if INR rises; hold if >4.5 or if bleeding.
- Renal function and electrolytes daily initially; watch for deterioration.
- Glucose with meals and as needed; avoiding fluoroquinolones reduces but does not eliminate dysglycemia risk in a diabetic inpatient.
- QTc if other QT-prolonging drugs are added; keep potassium and magnesium normal.
- Clinical response at 48–72 h: temperature, oxygen requirement, respiratory rate, white blood cell count.
Counsel the patient:
- Report tendon pain, swelling or a snap in the heel or shoulder immediately; stop the drug.
- Report diarrhea, especially if severe or bloody (C. difficile).
- Report easy bruising, black stools or blood in urine (warfarin effect).
- Tell staff about dizziness, palpitations or fainting.
- Complete the antibiotic course; do not share or save antibiotics.