What is the recommended dosing schedule for oral cefepime (Cefepime) and tobramycin (Tobramycin) for a patient with a difficult-to-heal leg ulcer positive for Pseudomonas aeruginosa, and what is the typical duration of treatment?

Critical Error: Oral Cefepime and Tobramycin Do Not Exist

Cefepime is only available as an intravenous formulation, and tobramycin for systemic Pseudomonas infections is only available intravenously or via inhalation—neither drug has an oral formulation for treating systemic infections. 1, 2

Correct Treatment Approach for Pseudomonas Leg Ulcer

First-Line Oral Antibiotic Option

For a difficult-to-heal leg ulcer with Pseudomonas aeruginosa, ciprofloxacin 750 mg orally twice daily for 14 days is the only reliable oral antibiotic option. 3, 4, 5

• Ciprofloxacin achieves sputum concentrations 46-90% of serum levels and has excellent tissue penetration 2
• The 750 mg twice-daily dose (not 500 mg) is essential for adequate Pseudomonas coverage 4, 5
• Standard duration is 14 days for Pseudomonas infections 4

When Intravenous Therapy Is Required

Consider IV antibiotics if the patient has failed oral therapy, has severe infection, or has resistant organisms. 4

For IV therapy, the recommended regimens include:

• Cefepime 2 g IV every 8 hours (preferred for Pseudomonas) 2, 1, 6
• Piperacillin-tazobactam 4.5 g IV every 6 hours 3, 4
• Ceftazidime 2 g IV every 8 hours 2, 4

Combination Therapy Considerations

For severe infections or treatment failures, add a second antipseudomonal agent: 3, 7

• Tobramycin 5-7 mg/kg IV once daily (requires drug level monitoring) 2, 3, 7
• Combination therapy suppresses resistance development and improves outcomes 8, 7

Treatment Duration

• Soft tissue infections: 1-2 weeks 2
• Consider extending to 3-4 weeks if: 2
  • Infection is extensive and resolving slower than expected
  • Patient has severe peripheral artery disease
  • Osteomyelitis is present (requires 6 weeks if no bone resection) 2

Critical Pitfalls to Avoid

• Never underdose ciprofloxacin—500 mg twice daily is insufficient; use 750 mg twice daily 4, 5
• Do not use empirical Pseudomonas coverage in temperate climates unless previously isolated from the site 2
• Obtain culture and sensitivity before starting antibiotics to confirm susceptibility 4
• Re-evaluate after 4 weeks if infection has not resolved despite appropriate therapy 2
• Aminoglycoside monotherapy should never be used for systemic Pseudomonas infections due to rapid resistance emergence 3

Special Considerations for Diabetic Foot Infections

If this is a diabetic foot ulcer:

• Do not treat clinically uninfected ulcers with antibiotics 2
• Obtain bone samples (not soft tissue) for culture if osteomyelitis is suspected 2
• Urgent surgical consultation is needed for severe infection, extensive gangrene, or signs of deep abscess 2