Recommended Dosage of Unasyn (Ampicillin/Sulbactam) for Uncomplicated Cellulitis
The recommended dosage of Unasyn (ampicillin/sulbactam) for uncomplicated cellulitis in adults is 1.5 grams (1 gram ampicillin plus 0.5 grams sulbactam) to 3 grams (2 grams ampicillin plus 1 gram sulbactam) administered intravenously every 6 hours for 5-6 days. 1, 2
Dosing Considerations
Adult Dosing
- Standard dose: 1.5-3 grams IV every 6 hours 1
- Total daily dose: 6-12 grams divided into 4 doses
- Duration: 5-6 days for uncomplicated cellulitis 2, 3
- Maximum sulbactam dose: Should not exceed 4 grams per day 1
Pediatric Dosing
- For children ≥1 year: 300 mg/kg/day IV divided into equal doses every 6 hours (corresponds to 200 mg ampicillin/100 mg sulbactam per kg per day) 1
- Children weighing ≥40 kg: Use adult dosing recommendations 1
- Maximum sulbactam dose: Should not exceed 4 grams per day 1
Renal Impairment Adjustments
Dosage adjustment is required based on creatinine clearance 1:
- CrCl ≥30 mL/min: 1.5-3 grams every 6-8 hours
- CrCl 15-29 mL/min: 1.5-3 grams every 12 hours
- CrCl 5-14 mL/min: 1.5-3 grams every 24 hours
Administration
- IV administration: Can be given by slow intravenous injection over 10-15 minutes or as an infusion in 50-100 mL of compatible diluent over 15-30 minutes 1
- IM administration: Can be administered by deep intramuscular injection 1
Treatment Duration
Recent guidelines from the American College of Physicians strongly recommend a shorter 5-6 day course of antibiotics for uncomplicated cellulitis 2, 3. This recommendation is supported by research showing that shorter courses are as effective as longer courses for uncomplicated cellulitis 4.
Clinical Considerations
When to Consider Hospitalization
Hospitalization should be considered if 2, 3:
- There is concern for deeper or necrotizing infection
- Patient has poor adherence to therapy
- Infection is in a severely immunocompromised patient
- Outpatient treatment is failing
- Patient shows signs of systemic inflammatory response syndrome (SIRS)
- Patient has altered mental status or hemodynamic instability
Alternative Antibiotic Options
For non-purulent cellulitis, other treatment options include 3:
- Cephalexin
- Penicillins
- Clindamycin
If MRSA coverage is needed (for purulent cellulitis or specific risk factors), options include 2, 3:
- TMP-SMX
- Clindamycin
- Doxycycline or minocycline
- Linezolid
Prevention of Recurrent Cellulitis
For patients with recurrent cellulitis 2, 3:
- Identify and treat predisposing conditions (edema, obesity, eczema, venous insufficiency)
- Maintain good personal hygiene
- Keep draining wounds covered with clean, dry bandages
- Avoid reusing or sharing personal items
- Consider prophylactic antibiotics for patients with 3-4 episodes per year
Monitoring Response
- Daily follow-up until definite improvement is noted 3
- Consider extending treatment if infection has not improved after 5 days 3
- Watch for warning signs of deeper infection, including pain disproportionate to physical findings 3
The evidence strongly supports that a 5-6 day course of Unasyn is sufficient for uncomplicated cellulitis, which aligns with the broader trend toward shorter antibiotic courses for common infections to reduce antibiotic resistance and adverse effects.