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[Pharmacology](https://durgical.com/en/pharmacology/) · [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/)

# Ampicillin + sulbactam

Ampicillin protected by sulbactam for mixed intra-abdominal, gynaecological and skin infections.

Updated 2026-11-01

- Class: [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/)
- Enzyme: Bacterial PBPs (ampicillin) and β-lactamases (sulbactam)
- ATC code: J01CR01

Also called: ampicillin–sulbactam

✂**Bacterial PBPs (ampicillin) and β-lactamases (sulbactam)**Ampicillin + sulbactam

ⓘ The figure shows sulbactam in the SHV-1 β-lactamase of Klebsiella pneumoniae (E166A variant), trapped as a trans-enamine intermediate in the active site.

**Target in 3D:** Bacterial PBPs (ampicillin) and β-lactamases (sulbactam). PDB structure 2A3U (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/2A3U) · Drag to rotate · pinch to zoom

## Mechanism of action

Ampicillin acylates the PBPs, but β-lactamases break it down. Sulbactam, a penicillin sulfone, irreversibly inhibits many of those β-lactamases and restores ampicillin's activity against methicillin-susceptible S. aureus, H. influenzae, enteric bacteria and anaerobes such as Bacteroides. On its own, sulbactam has little useful antibacterial action, except against the Neisseriaceae.

- Sulbactam binds the β-lactamase and inactivates it
- Ampicillin stays intact and reaches the PBPs
- Peptidoglycan cross-linking is blocked
- The wall fails and the bacterium lyses

## Pharmacokinetics

**Absorption**
Intravenous or intramuscular only.

**Elimination**
Both components leave unchanged in the urine; adjusted in kidney failure.

**Half-life**
About 1 hour for both in healthy people.

## Indications

- Intra-abdominal infections. [Peritonitis →](https://durgical.com/en/conditions/peritonitis/)
- Gynaecological infections such as endometritis and pelvic inflammatory disease. [Pelvic inflammatory disease →](https://durgical.com/en/conditions/pelvic-inflammatory-disease/)
- Skin and soft-tissue infections. [Cellulitis of the leg →](https://durgical.com/en/conditions/cellulitis-of-the-leg/)

## Adverse effects

### Common

- Injection-site pain and phlebitis
- Diarrhoea, rash
- Transient rise in transaminases

### Serious (rare, important)

- Anaphylaxis
- Severe skin reactions (Stevens–Johnson, toxic epidermal necrolysis, DRESS, acute generalised exanthematous pustulosis)
- Liver toxicity, including cholestatic jaundice
- Clostridioides difficile diarrhoea, from mild to severe colitis

## Contraindications

- History of a serious hypersensitivity reaction (anaphylaxis, Stevens–Johnson syndrome) to any penicillin or other β-lactam
- Previous cholestatic jaundice or liver dysfunction linked to ampicillin + sulbactam

## Key interactions

**Probenecid**
Reduces tubular secretion: higher and longer-lasting β-lactam levels.

**Allopurinol**
Raises the rate of rash with aminopenicillins.

**Aminoglycosides (in the same mixture)**
Ampicillin inactivates them in vitro; they are reconstituted and given separately.

## What is monitored

- Liver tests if jaundice or liver disease
- Kidney function and blood count in long courses

## Administration and safety

- Intravenous (slow injection or infusion) or deep intramuscular.
- Do not mix with aminoglycosides in the same syringe or bag.
- Do not confuse with plain ampicillin: the spectrum is different.

## Nursing care

- Before the first dose: ask about allergy to penicillins, cephalosporins and other β-lactams, and what the reaction was.
- After the first dose, watch for hives, wheeze, low blood pressure or swelling of lips and tongue, with anaphylaxis equipment at hand.
- Check the IV site for phlebitis.
- Watch for jaundice, dark urine or itching.
- Teach the patient to report watery or bloody diarrhoea, even weeks after the course ends.

## Pregnancy and breastfeeding

Animal studies showed no fetal harm and there are no controlled studies in pregnant women; used when clearly needed.

## Memory aid

'Sulbactam shields': it hardly kills bacteria itself, it only shields ampicillin from β-lactamases.

## Test yourself

Think of the answer, then tap the question to see it.

## Why is sulbactam not used alone as an antibiotic?

Because on its own it has little useful antibacterial activity (except against the Neisseriaceae); its job is to inhibit the β-lactamases that would destroy ampicillin.

## Why does ampicillin + sulbactam cover anaerobes such as Bacteroides while ampicillin alone does not?

Because Bacteroides makes β-lactamases that destroy ampicillin; sulbactam inhibits them.

## Which liver history rules out the combination?

Previous cholestatic jaundice or liver dysfunction linked to ampicillin + sulbactam.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/ampicillin-sulbactam/)

## Related drugs

- [Ampicillin](https://durgical.com/en/pharmacology/ampicillin/)
- [Amoxicillin + clavulanic acid](https://durgical.com/en/pharmacology/amoxicillin-clavulanic-acid/)
- [Piperacillin + tazobactam](https://durgical.com/en/pharmacology/piperacillin-tazobactam/)

## Related conditions

- [Peritonitis](https://durgical.com/en/conditions/peritonitis/)
- [Pelvic inflammatory disease](https://durgical.com/en/conditions/pelvic-inflammatory-disease/)
- [Cellulitis of the leg](https://durgical.com/en/conditions/cellulitis-of-the-leg/)

[← Back to the class: Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Ampicillin and Sulbactam Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a693021.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - AMPICILLIN AND SULBACTAM injection, powder, for solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a67ae347-487d-4751-a841-b321e81db26f) (DailyMed (U.S. National Library of Medicine), 2026); [RCSB PDB - 2A3U: Crystal structure of sulbactam bound to E166A variant of SHV-1 beta-lactamase](https://www.rcsb.org/structure/2A3U) (RCSB Protein Data Bank, 2026); Farmacología básica y clínica (Katzung), cap. 43 (McGraw Hill, 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/ampicillin-sulbactam/