ampicillin/sulbactam
Brand names: Unasyn
Unasyn is a combination of two antibiotics that fights bacteria in your body. It contains ampicillin and sulbactam.
Drug Shortage Alert
ampicillin/sulbactam is currently listed as to be discontinued by the FDA. Affected manufacturer: Sandoz Inc..
View all drug shortages →What it does
Unasyn treats skin infections, infections in the stomach area, and infections in women's reproductive organs.
Common side effects
Pain at the injection site, Diarrhea, Rash
Key warnings
You should not take Unasyn if you have had a severe allergic reaction to penicillins or cephalosporins.
How It Works
Ampicillin kills bacteria. Sulbactam helps ampicillin work better by preventing bacteria from breaking down ampicillin. Together, they stop the growth of bacteria.
How to Take It
Unasyn is given through a vein (IV) over 10-30 minutes. Adults usually receive 1.5 to 3 grams every 6 hours. Children 1 year and older usually receive 300 mg per kg of body weight per day, divided into doses every 6 hours. Treatment usually lasts no more than 14 days.
Pregnancy & Breastfeeding
Tell your doctor if you are pregnant or plan to become pregnant. It is not known if Unasyn will harm your unborn baby. Talk to your doctor about the risks and benefits of taking Unasyn while breastfeeding.
Missed Dose
Since Unasyn is given by a healthcare provider, you are not likely to miss a dose.
Storage
Store Unasyn sterile powder at or below 86°F (30°C) before mixing.
Side Effects (from patient reports)
Based on 417 FDA adverse event reports.
Serious Warnings
You should not take Unasyn if you have had a severe allergic reaction to penicillins or cephalosporins. You should also not take it if you have had liver problems caused by Unasyn in the past.
Known Drug Interactions
The concurrent administration of allopurinol and ampicillin increases substantially the incidence of rashes in patients receiving both drugs as compared to patients receiving ampicillin alone. It is not known whether this potentiation of ampicillin rashes is due to allopurinol or the hyperuricemia present in these patients. There are no data with UNASYN and allopurinol administered concurrently.
Mechanism: Taking these two medicines at the same time significantly increases your chances of developing a skin rash.
What to do: Tell your doctor immediately if you notice any new skin redness or itchy spots while taking these drugs.
Drug Interactions Probenecid decreases the renal tubular secretion of ampicillin and sulbactam. Concurrent use of probenecid with UNASYN may result in increased and prolonged blood levels of ampicillin and sulbactam.
Mechanism: One medicine slows down how fast your kidneys remove the antibiotic, which causes the antibiotic to stay in your blood longer.
What to do: Your doctor may need to adjust your dose or monitor you for side effects since the medicine stays in your system longer.
Common Questions
What if I have kidney problems?
Can Unasyn interact with other medications?
What are the signs of an allergic reaction?
Can Unasyn cause liver problems?
What lab tests will be done while I'm on Unasyn?
What should I do if I experience pain at the injection site?
Can Unasyn cause diarrhea?
Is it okay to drink alcohol while taking Unasyn?
What should I do if my symptoms don't improve?
Can Unasyn cause a yeast infection?
What are the common side effects of ampicillin/sulbactam?
Does ampicillin/sulbactam interact with other medications?
What drug class is ampicillin/sulbactam?
Is ampicillin/sulbactam safe during pregnancy?
Is ampicillin/sulbactam currently in shortage?
Related Medications in Penicillin / Beta-Lactamase Inhibitor
Other drugs grouped near ampicillin/sulbactam — same-class peers and common alternatives.
amikacin
Amikin
Amikacin is an antibiotic medicine.
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amoxicillin
Amoxil
Amoxicillin and Clavulanate Potassium is a combination medicine used to fight bacterial infections.
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amoxicillin/clavulanate
Augmentin
Augmentin is a combination of two medicines, amoxicillin and clavulanate.
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azithromycin
Zithromax, Z-Pack
Azithromycin is an antibiotic that fights bacteria.
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cefazolin
Ancef, Kefzol
Cefazolin is an antibiotic medicine.
Compare with ampicillin/sulbactam →
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What the FDA Data Shows for ampicillin/sulbactam
The FDA label for ampicillin/sulbactam (sold under brand names such as Unasyn) classifies it as a prescription-only medication in the Penicillin / Beta-Lactamase Inhibitor class. Unasyn treats skin infections, infections in the stomach area, and infections in women's reproductive organs. Official labeling lists 3 commonly reported side effects, including Pain at the injection site, Diarrhea, Rash.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 417 voluntary reports. The database also lists 2 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. Acquisition-cost data is surveyed weekly by CMS and updated as manufacturers report changes.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Shortage status: FDA Drug Shortages Database.
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: May 14, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages