What is the dosage and treatment duration for Unasyn (ampicillin/sulbactam) for bacterial infections?

Dosage and Treatment Duration for Unasyn (Ampicillin/Sulbactam) for Bacterial Infections

For adult patients with bacterial infections, Unasyn (ampicillin/sulbactam) should be administered at a dosage of 1.5-3 g every 6 hours intravenously, with treatment duration typically ranging from 7-14 days depending on the infection type and clinical response. 1

Standard Adult Dosing

• Standard adult dose: 1.5 g (1 g ampicillin + 0.5 g sulbactam) to 3 g (2 g ampicillin + 1 g sulbactam) every 6 hours IV 1
• Maximum daily dose: Total sulbactam component should not exceed 4 grams per day 1
• Administration method:
  • Slow IV injection over 10-15 minutes, or
  • IV infusion diluted in 50-100 mL compatible solution over 15-30 minutes 1

Pediatric Dosing

• Children ≥1 year: 300 mg/kg/day divided every 6 hours IV (equivalent to 200 mg ampicillin + 100 mg sulbactam per kg per day) 1, 2
• Children ≥40 kg: Use adult dosing recommendations 1
• Maximum treatment duration: Should not routinely exceed 14 days IV 1

Dosage Adjustment for Renal Impairment

Creatinine Clearance	Dosage Adjustment
≥30 mL/min	1.5-3 g every 6-8 hours
15-29 mL/min	1.5-3 g every 12 hours
5-14 mL/min	1.5-3 g every 24 hours

Infection-Specific Dosing and Duration

Skin and Soft Tissue Infections

• Necrotizing infections: 1.5-3 g every 6-8 hours IV 3
• Mixed infections: Ampicillin-sulbactam may be combined with clindamycin and ciprofloxacin for severe mixed infections 3
• Infections involving axilla or perineum: Ampicillin-sulbactam is a drug of choice 3
• Duration: 7-14 days, depending on severity and clinical response 4

Intra-abdominal Infections

• Standard dosing: 1.5-3 g every 6 hours IV 3
• Duration: Typically 7-10 days, but may be shorter with adequate source control 3
• Pediatric intra-abdominal infections: 300 mg/kg/day divided every 6 hours 3, 2

Acinetobacter baumannii Infections

• Severe infections: Higher dosing of 9-12 g/day of sulbactam component in 3 daily doses may be required 3
• Administration: 4-hour infusion recommended for resistant strains 3
• Duration: Typically 10-14 days depending on infection severity and clinical response 3

Clinical Considerations and Pitfalls

1. Resistance concerns:

   • Monitor for increasing sulbactam MICs in Acinetobacter baumannii 3
   • Consider susceptibility testing before treatment of resistant pathogens 3

2. Combination therapy:

   • For necrotizing infections, consider combining with clindamycin and ciprofloxacin 3
   • For multidrug-resistant Acinetobacter, sulbactam-containing regimens may be more effective than other options 3

3. Common adverse effects:

   • Generally well-tolerated in both adults and children 2, 4
   • Pain at injection site is the most commonly reported adverse effect 5

4. Treatment monitoring:

   • Clinical response should be evident within 48-72 hours
   • Consider follow-up cultures in case of treatment failure 3

Special Situations

• Penicillin allergy: Avoid in patients with severe penicillin hypersensitivity 3
• Urogenital infections: Treatment course typically 7-10 days with daily doses of 6-9 g 5
• Pediatric skin infections: Treatment is effective and well-tolerated, with clinical cure rates comparable to cefuroxime 4

Remember that while the FDA-approved duration for IV therapy should not routinely exceed 14 days, the actual duration should be guided by the type and severity of infection, clinical response, and source control measures.