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

Dosage and Treatment Duration for Unasyn (Ampicillin/Sulbactam)

The recommended adult dosage of Unasyn (ampicillin/sulbactam) for bacterial infections is 1.5 g to 3 g every 6 hours intravenously, with treatment duration typically ranging from 5-14 days depending on the infection type and clinical response. 1

Adult Dosing

Standard Adult Dosing

• 1.5 g (1 g ampicillin + 0.5 g sulbactam) to 3 g (2 g ampicillin + 1 g sulbactam) IV every 6 hours 1
• Can be administered by slow IV injection (over 10-15 minutes) or as an infusion (diluted in 50-100 mL over 15-30 minutes)
• Maximum daily sulbactam dose: 4 grams 1
• IM administration is also possible for deep intramuscular injection

Dosing for Specific Infections

• Skin and Soft Tissue Infections:

  • Mixed infections: 1.5-3 g every 6-8 hours IV 2
  • Necrotizing infections: 1.5-3 g every 6-8 hours IV 2

• Intra-abdominal Infections:

  • Adults: 1.5-3 g every 6 hours IV 2
  • For carbapenem-resistant Acinetobacter baumannii: 6-9 g of sulbactam component per day (higher doses) 2

Renal Impairment Dosing Adjustments

• Creatinine clearance ≥30 mL/min/1.73m²: 1.5-3 g every 6-8 hours
• Creatinine clearance 15-29 mL/min/1.73m²: 1.5-3 g every 12 hours
• Creatinine clearance 5-14 mL/min/1.73m²: 1.5-3 g every 24 hours 1

Pediatric Dosing

• Children ≥1 year of age: 300 mg/kg/day IV divided every 6 hours (equivalent to 200 mg ampicillin + 100 mg sulbactam per kg per day) 1
• Children ≥40 kg: Use adult dosing recommendations 1
• For skin and skin structure infections: 150-300 mg/kg/day in divided doses every 6 hours 3
• For intra-abdominal infections: 200 mg/kg/day of ampicillin component 2

Treatment Duration

Treatment duration varies by infection type:

• Urinary tract infections: 5-7 days 2, 4
• Skin and soft tissue infections: 7-10 days 2, 3
• Intra-abdominal infections: 5-7 days 2
• Respiratory infections: 7-14 days
• Bacteremia: 10-14 days 2

The IV therapy course should not routinely exceed 14 days 1. Many pediatric patients may transition to oral antimicrobials following initial IV therapy 1.

Clinical Considerations

Advantages

• Effective against beta-lactamase-producing organisms due to sulbactam's inhibition of beta-lactamases 5
• Particularly useful for mixed infections with both gram-positive and gram-negative organisms 2
• Shows activity against Acinetobacter baumannii, even some multidrug-resistant strains 2, 6

Monitoring

• Monitor renal function, especially in patients with pre-existing renal impairment
• Watch for signs of hypersensitivity reactions
• For prolonged therapy, monitor for superinfection

Common Pitfalls

1. Underdosing: Using insufficient doses for severe infections, particularly for resistant organisms like Acinetobacter baumannii
2. Failure to adjust for renal function: Not modifying dosing intervals in patients with impaired renal function
3. Inadequate duration: Stopping therapy prematurely before complete resolution of infection
4. Not considering local resistance patterns: Effectiveness may vary based on local antimicrobial susceptibility patterns

Unasyn provides effective coverage for many common bacterial pathogens and is particularly valuable for polymicrobial infections due to its broad spectrum of activity against both gram-positive and gram-negative organisms, including many beta-lactamase producers.