ampicillin-sulbactam
Brand: Unasyn
Prototype: amoxicillin-clavulanate
Drug Class: antibiotic (beta-lactam/beta-lactamase inhibitor combination)
Drug Family: antibiotic
Subclass: aminopenicillin + beta-lactamase inhibitor
Organ Systems: infectious-disease
Mechanism of Action
Ampicillin inhibits PBPs; sulbactam irreversibly inhibits beta-lactamases, restoring ampicillin activity against beta-lactamase-producing organisms. Sulbactam itself has intrinsic antibacterial activity against Acinetobacter baumannii (via PBP2 binding), which is clinically relevant for treating MDR Acinetobacter infections.
penicillin-binding proteinsbeta-lactamase (inhibition by sulbactam)Acinetobacter (sulbactam has intrinsic activity)
Indications
- skin and soft tissue infections
- intra-abdominal infections
- pelvic inflammatory disease
- aspiration pneumonia
- MDR Acinetobacter infections (high-dose sulbactam)
Contraindications
- penicillin or sulbactam allergy (anaphylaxis)
Adverse Effects
Common
- diarrhea
- nausea
- injection site reactions
- rash
Serious
- anaphylaxis
- C. difficile colitis
- hepatotoxicity (rare)
Pharmacokinetics (ADME)
| Absorption | IV or IM only |
| Distribution | protein binding ampicillin 15-25%, sulbactam 38%; good tissue penetration |
| Metabolism | minimal hepatic |
| Excretion | renal; both components excreted unchanged |
| Half-life | 1 hour (both components) |
| Onset | end of IV infusion |
| Peak | end of infusion |
| Duration | 6 hours |
| Protein Binding | ampicillin 15-25%; sulbactam 38% |
| Vd | 0.3 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| aminoglycosides | synergistic; physically incompatible in same line | moderate |
Nursing Considerations
- Reconstituted solution is time-sensitive; use within manufacturer-specified timeframe after reconstitution.
- For MDR Acinetobacter infections, high-dose extended-infusion sulbactam protocols may be used; verify institutional protocol.
- Monitor for signs of C. difficile during and after treatment; diarrhea warrants stool testing.
- Dose adjustment required in renal impairment; CrCl <30 mL/min requires extended dosing interval.
Clinical Pearls
- Sulbactam unique intrinsic antibacterial activity against Acinetobacter baumannii (via PBP2 binding) has made high-dose sulbactam (ampicillin-sulbactam) a key option for carbapenem-resistant Acinetobacter infections.
- Ampicillin-sulbactam covers polymicrobial infections (gram-positives, many gram-negatives, anaerobes) making it useful for aspiration pneumonia, intra-abdominal, and skin/soft tissue infections.
Safety Profile
Pregnancy safe
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.