What is the recommended dose for oral ampicillin (AMP) - sulbactam (SUL)?

Oral Ampicillin-Sulbactam Dosing

There is no oral formulation of ampicillin-sulbactam available; this combination is only administered intravenously or intramuscularly. 1

Key Clinical Points

• Ampicillin-sulbactam (Unasyn) exists only as a parenteral formulation and cannot be given orally 1

• The oral alternative mentioned in guidelines is amoxicillin-clavulanate 875/125 mg twice daily, which provides similar beta-lactam/beta-lactamase inhibitor coverage for conditions like animal bites and soft tissue infections 1

Why This Matters Clinically

• Ampicillin has poor oral bioavailability (approximately 40-50%), making it unsuitable for oral formulation in combination products for serious infections

• When transitioning from IV ampicillin-sulbactam to oral therapy, amoxicillin-clavulanate is the appropriate oral step-down agent as it provides comparable antimicrobial coverage 1

Standard IV Dosing for Reference

Since oral administration is not possible, the standard IV dosing includes:

• Moderate infections: 1.5-3.0 g every 6 hours IV 1
• Severe infections or multidrug-resistant organisms: 9-12 g/day of sulbactam component (equivalent to 3 g ampicillin-sulbactam every 6 hours) with 4-hour extended infusions 2, 3
• Animal/human bite infections: 1.5-3.0 g every 6-8 hours IV 1

Common Pitfall to Avoid

• Do not attempt to prescribe "oral ampicillin-sulbactam" - this formulation does not exist and any such prescription would be unfillable 1
• When oral therapy is appropriate, switch to amoxicillin-clavulanate rather than searching for an oral ampicillin-sulbactam product 1