Prescription medication · Penicillin / Beta-Lactamase Inhibitor

ampicillin/sulbactam

Also sold as Unasyn. Unasyn treats skin infections, infections in the stomach area, and infections in women's reproductive organs.

Data updated 2026-05-15

351
FDA reports
2
InteractionsFew interactions
In shortage
FDA status

What the data shows

ampicillin/sulbactam (Unasyn) is a prescription Penicillin / Beta-Lactamase Inhibitor, with 351 FDA adverse-event reports on file, with 2 documented drug interactions.

Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.

ampicillin/sulbactam (Unasyn) is a prescription Penicillin / Beta-Lactamase Inhibitor. Unasyn treats skin infections, infections in the stomach area, and infections in women's reproductive organs.

Unasyn is a combination of two antibiotics that fights bacteria in your body. It contains ampicillin and sulbactam.

Verify with FDA → · CMS NADAC pricing →

Drug Shortage Alert

ampicillin/sulbactam is currently listed as to be discontinued by the FDA. Affected manufacturer: Sandoz Inc..

View all drug shortages →
View Alternatives → Compare with Another Drug →

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.

The sections below are summarized in plain English from ampicillin/sulbactam's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.

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.

Side Effects (from patient reports)

Based on 351 FDA adverse event reports.

Most-reported reactions

Adverse reactions in FAERS for ampicillin/sulbactam, by number of reports

reports

What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.

Source FDA Adverse Event Reporting System (FAERS)

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

minor allopurinol

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.

minor probenecid

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.

This is a plain-language summary of FDA-label interaction records and does not provide individual medication-combination directions.

Common Questions

What if I have kidney problems?
Your doctor may need to adjust your dose if you have kidney problems. They will give you the medicine less often.
Can Unasyn interact with other medications?
Yes, Unasyn can interact with probenecid, allopurinol, and aminoglycosides. Tell your doctor about all the medicines you take.
What are the signs of an allergic reaction?
Signs of an allergic reaction include rash, itching, swelling, trouble breathing, and throat tightness. Get medical help right away if you have any of these symptoms.
Can Unasyn cause liver problems?
Yes, Unasyn can cause liver problems, including cholestatic jaundice and hepatitis. Tell your doctor if you develop yellowing of the skin or eyes, dark urine, or abdominal pain.
What lab tests will be done while I'm on Unasyn?
Your doctor may order blood tests to check your liver function, kidney function, and blood cell counts.
What should I do if I experience pain at the injection site?
Tell your nurse or doctor if you have pain, swelling, or redness at the injection site.
Can Unasyn cause diarrhea?
Yes, diarrhea is a common side effect of Unasyn. If you develop severe diarrhea, especially with fever or blood in your stool, tell your doctor right away.
Is it okay to drink alcohol while taking Unasyn?
It's best to avoid alcohol while taking Unasyn, as it could worsen some side effects or interfere with the medication's effectiveness.
What should I do if my symptoms don't improve?
If your symptoms don't improve after a few days of treatment, contact your doctor.
Can Unasyn cause a yeast infection?
Yes, Unasyn can sometimes cause yeast infections (candidiasis). If you develop symptoms like itching or discharge, talk to your doctor.
What are the common side effects of ampicillin/sulbactam?
The registry lists Pain at the injection site, Diarrhea, Rash among the most-reported FAERS reaction terms for ampicillin/sulbactam. The compiled record contains 351 FDA adverse-event reports. These counts are not an individual symptom assessment.
Does ampicillin/sulbactam interact with other medications?
The registry has 2 documented interaction rows for ampicillin/sulbactam. Notable source-record pairings include allopurinol, probenecid. These rows are not a complete medication review.
What drug class is ampicillin/sulbactam?
ampicillin/sulbactam belongs to the Penicillin / Beta-Lactamase Inhibitor drug class. It requires a prescription (Rx). Unasyn treats skin infections, infections in the stomach area, and infections in women's reproductive organs.
What pregnancy or breastfeeding source fields are listed for ampicillin/sulbactam?
The FDA label for ampicillin/sulbactam contains product-specific pregnancy or breastfeeding language. PlainMeds does not apply that source text to an individual.
Is ampicillin/sulbactam currently in shortage?
Yes, ampicillin/sulbactam is currently listed as to be discontinued by the FDA. Affected manufacturer: Sandoz Inc.. Visit the FDA Drug Shortages database for the latest updates.

Related Medications in Penicillin / Beta-Lactamase Inhibitor

Other drugs grouped near ampicillin/sulbactam - same-class peers and common alternatives.

amikacin

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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.

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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 351 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 are separate source-record fields. This page is a public FDA/CMS registry and does not provide medical, treatment, substitution, or medication-change directions.

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. This registry does not provide medication decisions.

Last updated: May 14, 2025

PlainMeds is rendered directly from FDA openFDA/FAERS extracts, DailyMed labels, and CMS drug-pricing files, no number is typed in by an editor. FAERS counts, recalls, shortages, and price figures on this page are queried live from those federal extracts. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-05-15. Primary sources: openFDA / FAERS, DailyMed and CMS Part B ASP.

Read our methodology - how this data is sourced, computed, and verified.

Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled from the source snapshot dated . See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a data issue.

All federal data sources used on this page