Unasyn (ampicillin/sulbactam)

Pronunciation: am-pi-SIL-in / sul-BAK-tam.

Generic name
ampicillin sodium and sulbactam sodium
Drug class
Beta-lactam antibiotic (aminopenicillin) plus beta-lactamase inhibitor combination
Form
Powder for solution for injection/infusion (1.5 g, 3 g single-dose vials; 15 g pharmacy bulk package)
Route
Intravenous or intramuscular injection
Legal status
Prescription-only, hospital/clinic-administered

Availability and supply rules vary by country

Trade names by country: United States

Australia: · Full directory

What ampicillin sodium and sulbactam sodium is and how it works

Unasyn is an injectable antibiotic combination used in hospitals and clinics to treat bacterial infections, including certain skin, abdominal, and gynaecological infections, when the responsible bacteria are known or expected to respond to it. (1)

Unasyn is given into a vein or muscle by trained clinical staff -- it is not a medicine you take home or self-administer. Its most important risks are a serious allergic reaction (a known risk with all penicillin-type antibiotics) and a type of antibiotic-associated diarrhoea called C. difficile colitis, which can occur even after the course has finished.

Mechanism of action: how ampicillin sodium and sulbactam sodium works

Ampicillin is an aminopenicillin that inhibits bacterial cell wall synthesis. Sulbactam is a beta-lactamase inhibitor with minimal intrinsic antibacterial activity that irreversibly binds many bacterial beta-lactamase enzymes, protecting ampicillin from enzymatic degradation and extending its activity against beta-lactamase-producing organisms. (1)

What ampicillin sodium and sulbactam sodium is used for

Bacterial infections of the skin, abdomen, and female reproductive organs

Used to treat skin and skin-structure infections, intra-abdominal infections, and gynaecological infections caused by bacteria that are susceptible to ampicillin or that produce an enzyme (beta-lactamase) which sulbactam can overcome. (1)

Before taking ampicillin sodium and sulbactam sodium

Do not take / not appropriate for

  • Should not be given to anyone with a history of a serious allergic reaction (such as anaphylaxis or Stevens-Johnson syndrome) to ampicillin, sulbactam, or any penicillin-type or related beta-lactam antibiotic. (all countries where authorised) (1)
  • Should not be given to anyone with a previous history of liver problems (cholestatic jaundice or liver dysfunction) linked to this medicine. (all countries where authorised) (1)

Tell your clinician about

  • Any history of allergic reactions to penicillin, cephalosporins, or other antibiotics.
  • Any kidney problems -- your dose and dosing interval depend on your kidney function.
  • Any liver problems.
  • Any history of antibiotic-associated diarrhoea or colitis.
  • All other medicines, including probenecid, allopurinol, and aminoglycoside antibiotics.
  • Whether you are pregnant, plan to become pregnant, or are breastfeeding.
(1)

How to take ampicillin sodium and sulbactam sodium

  • Given only by trained clinical staff, as an injection into a vein (usually over 15-30 minutes) or into a muscle.
  • Never self-administered or taken home in the way an oral antibiotic would be.
  • Not reconstituted or mixed in the same syringe or container as an aminoglycoside antibiotic, since this can inactivate both medicines.
  • Your dose, frequency, and duration are individually set by your clinical team based on the infection being treated, your kidney function, and your weight (for children).
(1)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

Since Unasyn is given on a schedule set by your hospital or clinic team, contact them directly with any questions about timing -- this is not a medicine where you manage your own dosing schedule.

Overdose

Because Unasyn is administered by clinical staff, any concern about an excessive dose is managed directly by the treating team, with supportive care as needed. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Diarrhoea.

What to notice: Diarrhoea.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Pain, redness, or irritation at the injection site.

What to notice: Pain, redness, or irritation at the injection site.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Rash.

What to notice: Rash.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Vein irritation (thrombophlebitis) with intravenous use.

What to notice: Vein irritation (thrombophlebitis) with intravenous use.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Serious warnings

Signs of a serious allergic reaction (anaphylaxis) — emergency

Symptoms: Swelling of the face, lips, tongue, or throat; difficulty breathing; widespread rash or hives; sudden dizziness or fainting.

Action: Seek emergency medical help immediately. Serious and occasionally fatal allergic reactions have occurred with penicillin-class antibiotics, and people with a known penicillin allergy have a higher chance of reacting to related antibiotics too. (1)

Signs of C. difficile-associated diarrhoea (antibiotic-associated colitis) — emergency

Symptoms: Watery or bloody diarrhoea, stomach cramps, or fever, which can start during treatment or up to about 2 months after it ends.

Action: Contact your clinician or seek medical care promptly -- this can range from mild to severe and needs assessment even after the antibiotic course has finished. (1)

Signs of a severe skin reaction — emergency

Symptoms: Widespread blistering or peeling skin, painful rash, or sores in the mouth, eyes, or genitals.

Action: Seek emergency medical help immediately -- rare but serious skin reactions (including toxic epidermal necrolysis and Stevens-Johnson syndrome) have been reported with this class of antibiotic. (1)

Signs of liver problems — high caution

Symptoms: Yellowing of the skin or eyes, dark urine, or unusual tiredness.

Action: Tell your clinical team promptly -- liver effects are usually reversible but should be assessed quickly, especially if you have existing liver problems. (1)

Interactions

  • Probenecid can raise and prolong ampicillin/sulbactam levels in the blood. (1)
  • Allopurinol, when combined with ampicillin-class antibiotics, has been associated with a higher rate of skin rash. (1)
  • Unasyn and aminoglycoside antibiotics must not be reconstituted or mixed together in the same container, since this inactivates both medicines -- they are given separately. (1)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Animal studies did not show harm at doses up to 10 times the human dose. Used in pregnancy only when clearly needed, as decided with your clinical team. (1) (2) (3) (4) (5) (6)

Breastfeeding

Low levels of ampicillin and sulbactam pass into breast milk; used with caution and discussed with your clinical team. (1) (2) (3) (4) (5) (6)

Children

Used from 1 year of age, dosed by body weight; children at or above adult body weight are dosed as adults. (1) (2) (3) (4) (5) (6)

Elderly

No specific dose adjustment based on age alone is described in the source reviewed, beyond the standard adjustment for reduced kidney function. (1) (2) (3) (4) (5) (6)

Hepatic_impairment

Contraindicated if you have had cholestatic jaundice or liver dysfunction linked to this medicine previously; liver function is monitored during treatment, especially with pre-existing liver problems. (1) (2) (3) (4) (5) (6)

Renal_impairment

Dosing interval is extended for reduced kidney function, following a defined creatinine-clearance-based schedule set by your clinical team. (1) (2) (3) (4) (5) (6)

Monitoring

Before starting

  • Culture and susceptibility testing where practical
  • Allergy history (penicillin and other antibiotics)
  • Kidney function
  • Liver function where relevant

During treatment

  • Clinical monitoring for signs of allergic reaction, especially with the first doses.
  • Watching for diarrhoea during and after treatment.
  • Liver function tests if there is pre-existing liver impairment or symptoms suggesting liver injury.
  • Kidney function to guide dosing interval, especially in longer courses.
(1)

Storage

Unopened powder is stored at or below 30C (86F). Once reconstituted, the solution is used within 2 hours at room temperature or 4 hours if refrigerated; further diluted solutions have their own separate stability windows -- all handled by hospital/clinic pharmacy staff, not stored at home.

Study the drug class: Penicillins

Professional information

Clinician-facing context only, sourced from the current US FDA prescribing information; verify against the current full label before prescribing.

United States

Indication: Skin/skin-structure, intra-abdominal, and gynaecological infections

Dose summary: Adults: 1.5-3 g IV every 6 hours (sulbactam capped at 4 g/day), infused over 15-30 minutes. Paediatric (>=1 year, <40 kg): 300 mg/kg/day divided every 6 hours. Renal dosing: CrCl >=30 q6-8h; 15-29 q12h; 5-14 q24h.

Renal context: Dosing interval extended stepwise as creatinine clearance falls below 30 mL/min, down to every 24 hours for CrCl 5-14 mL/min. (1)

Mechanism of action

Hepatic guidance

Hepatic effects are usually reversible, but rare fatalities have been reported; monitor liver function in patients with pre-existing hepatic impairment.

Overdose note

Managed with supportive care; high CSF levels of beta-lactam antibiotics have been associated with convulsions, particularly in renal impairment. (1)

Frequently asked questions

Is Unasyn (ampicillin/sulbactam) available in the US, UK, Europe, Canada, Australia, and New Zealand?

It is confirmed authorised in the United States (as Unasyn) and the European Union (as Unacid, authorised nationally in Germany and other member states). A live check of the UK's electronic medicines compendium and Australia's TGA product database found no listing for a sulbactam-containing product, and no current Health Canada or New Zealand Medsafe listing could be confirmed despite a genuine search -- so availability in the UK, Canada, and New Zealand could not be verified, and it does not appear to be currently registered in Australia. Always confirm local availability with a hospital pharmacist. (1) (2) (3) (4) (5) (6)

Is Unasyn safe if I am allergic to penicillin?

No -- Unasyn contains ampicillin, a penicillin-type antibiotic, and should not be given to anyone with a history of a serious allergic reaction to penicillins or related beta-lactam antibiotics. Always tell your clinical team about any antibiotic allergy before treatment. (1)

What symptoms during Unasyn treatment need prompt medical attention?

Tell your care team promptly about severe or watery diarrhoea (which can occur even weeks after finishing treatment), yellowing of the skin or eyes, or a new rash or blistering skin reaction. Seek emergency care immediately for signs of a severe allergic reaction such as swelling of the face or throat, difficulty breathing, or widespread hives. (1)

What is the mechanism of action of ampicillin sodium and sulbactam sodium?

Ampicillin is an aminopenicillin that inhibits bacterial cell wall synthesis. Sulbactam is a beta-lactamase inhibitor with minimal intrinsic antibacterial activity that irreversibly binds many bacterial beta-lactamase enzymes, protecting ampicillin from enzymatic degradation and extending its activity against beta-lactamase-producing organisms. (1)

What is the generic name of Unasyn (ampicillin/sulbactam)?

The generic name is ampicillin sodium and sulbactam sodium. (1)

What class of drug is ampicillin sodium and sulbactam sodium?

Unasyn (ampicillin/sulbactam) is classed as: Beta-lactam antibiotic (aminopenicillin) plus beta-lactamase inhibitor combination. (1)

References

  1. UNASYN (ampicillin sodium and sulbactam sodium) injection, powder, for solution -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information, Pfizer / Roerig · United States · accessed 2026-07-30 · source 1
  2. emc search for 'sulbactam' -- no products found; ampicillin-sodium ingredient page lists only single-ingredient ampicillin productelectronic medicines compendium (emc), United Kingdom -- ingredient and keyword search · United Kingdom · accessed 2026-07-30 · source 2
  3. Unacid (ampicillin/sulbactam) 500 mg/250 mg and 1000 mg/500 mg powder for injection/infusion -- FachinformationGermany -- Fachinformation (SmPC equivalent), Pfizer Pharma GmbH (EU national authorisation) · European Union · accessed 2026-07-30 · source 3
  4. Health Canada DPD search for ampicillin/sulbactam -- no current marketed human combination product confirmedHealth Canada Drug Product Database (DPD) -- search attempted, no current human combination product confirmed · Canada · accessed 2026-07-30 · source 4
  5. TGA eBS PICMI search for 'sulbactam' -- zero documents foundTherapeutic Goods Administration (TGA), Australia -- eBS/PICMI public product search · Australia · accessed 2026-07-30 · source 5
  6. No Medsafe data sheet or product listing located for ampicillin/sulbactam or UnasynMedsafe (New Zealand regulator) -- no data sheet located · New Zealand · accessed 2026-07-30 · source 6

Brand names by country

Single-ingredient ampicillin sodium and sulbactam sodium names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Unasyn (1)FDA approved currently labeled · 1.5 g (1 g/0.5 g), 3 g (2 g/1 g), 15 g pharmacy bulk package · Pfizer / Roerig
View brands in additional countries.

European Union

Unacid (3)

This page provides general reference information about Unasyn (ampicillin/sulbactam) and is not a substitute for advice from the clinical team administering your treatment. All dosing and treatment decisions are made by your hospital or clinic care team.

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Pharmacology