Unasyn (Ampicillin-Sulbactam) Usage in Treatment
Ampicillin-sulbactam (Unasyn) is not recommended for empiric treatment of community-acquired infections due to high rates of resistance among community-acquired E. coli strains, but it remains appropriate for specific indications including skin/soft tissue infections, intra-abdominal infections, and certain animal bite wounds when susceptibility is confirmed.
Indications for Ampicillin-Sulbactam
Ampicillin-sulbactam is FDA-approved for the following conditions 1:
- Skin and skin structure infections caused by beta-lactamase producing strains of Staphylococcus aureus, Escherichia coli, Klebsiella spp., Proteus mirabilis, Bacteroides fragilis, Enterobacter spp., and Acinetobacter calcoaceticus
- Intra-abdominal infections caused by beta-lactamase producing strains of E. coli, Klebsiella spp., Bacteroides spp., and Enterobacter spp.
- Gynecological infections caused by beta-lactamase producing strains of E. coli and Bacteroides spp.
Limitations and Resistance Concerns
Despite its broad spectrum of activity, ampicillin-sulbactam has important limitations:
- Not recommended for community-acquired infections due to high rates of resistance among community-acquired E. coli 2
- Not active against Pseudomonas aeruginosa 3
- Not effective against extended-spectrum beta-lactamase (ESBL) producing organisms 3
Specific Clinical Scenarios Where Ampicillin-Sulbactam May Be Appropriate
1. Animal Bite Wounds
Ampicillin-sulbactam is recommended for animal bite wounds due to its activity against Pasteurella multocida 2. For patients not allergic to penicillin, oral amoxicillin-clavulanate or intravenous ampicillin-sulbactam are appropriate options.
2. Acinetobacter Infections
For Acinetobacter species infections, ampicillin-sulbactam may be considered if the isolate is susceptible 2. This is due to the intrinsic activity of sulbactam against Acinetobacter baumannii 3.
3. Intra-abdominal Infections
For intra-abdominal infections with confirmed susceptibility, ampicillin-sulbactam may be used 1, though it's not a first-line empiric choice for community-acquired infections.
Alternative Therapies for Common Infections
For community-acquired infections where ampicillin-sulbactam is not recommended, consider:
For mild-to-moderate community-acquired intra-abdominal infections: Ticarcillin-clavulanate, cefoxitin, ertapenem, moxifloxacin, or tigecycline as single agents; or metronidazole combined with cefazolin, cefuroxime, ceftriaxone, cefotaxime, levofloxacin, or ciprofloxacin 2
For skin and soft tissue infections: Penicillinase-resistant semisynthetic penicillins or first-generation cephalosporins 2
Dosing Considerations
- Standard adult dosing: 3g IV (2g ampicillin/1g sulbactam) every 6 hours 1
- Intraoperative dosing: Every 2-4 hours during prolonged procedures 2
- Duration: Typically 7-10 days depending on the infection type and severity 4
Common Pitfalls and Caveats
Resistance monitoring: Always check local resistance patterns before empiric use, particularly for E. coli infections 2
Penicillin allergy: Consider alternative agents in patients with penicillin allergies 2
Susceptibility testing: Appropriate culture and susceptibility testing should be performed before treatment to ensure the causative organisms are susceptible to ampicillin-sulbactam 1
Inappropriate empiric use: Using ampicillin-sulbactam empirically for community-acquired infections may lead to treatment failure due to resistance 2
In conclusion, while ampicillin-sulbactam has valuable uses in specific clinical scenarios, its utility as an empiric agent for community-acquired infections is limited by increasing resistance patterns. Treatment decisions should be guided by local susceptibility data and, whenever possible, culture results.