ampicillin / sulbactam
Unasyn (ampicillin / sulbactam) is a combination medication that contains a penicillin and beta-lactamase inhibitor. This antibiotic is used to treat several types of infections throughout the body in adults and children. Doses are given as injections into the vein (IV) or muscle (IM) every 6 hours. Unasyn (ampicillin / sulbactam) is available as a brand-name medication and lower-cost generic. Side effects aren't common, but can include pain at the injection site and diarrhea.
What is Unasyn (ampicillin / sulbactam)?
What is Unasyn (ampicillin / sulbactam) used for?
Skin infections (e.g., cellulitis)
Gynecological infections (e.g., vaginal, cervical, pelvic inflammatory disease)
How Unasyn (ampicillin / sulbactam) works
Unasyn (ampicillin / sulbactam) is a combination of two medications that work together to treat infections.
Ampicillin is a type of penicillin antibiotic. It kills bacteria by preventing them from being able to make their cell walls (their outer covering) to protect themselves from harm.
Sulbactam is a beta-lactamase inhibitor. A beta-lactamase is a type of protein that bacteria make to break down ampicillin so that ampicillin can't work well. By blocking beta-lactamase from working, sulbactam protects ampicillin from being broken down so ampicillin can fight the infection better. Sulbactam can also work like an antibiotic and can kill a limited range of bacteria too.
Drug Facts
What are the side effects of Unasyn (ampicillin / sulbactam)?
Common Side Effects
- Pain at injection site (16% for IM injections, 3% for IV injections)
- Diarrhea (3%)
- Rash (up to 2%)
Other Side Effects
- Nausea
- Vomiting
- Headache
- Chest pain
- Itching
- Yeast infection
Serious Side Effects
- Serious allergic reaction or serious skin reaction: hives, rash, blisters, skin reddening, swelling of the lips or tongue, trouble breathing
- Infectious (C. difficile-related) diarrhea: rapid heart rate, foul-smelling diarrhea, frequent bowel movements (even up to 15 times per day), fever, nausea
- Liver problems: nausea, stomach pain, yellow skin or whites of the eyes, clay-colored stool, dark urine
Source: DailyMed
The following side effects have also been reported
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- Liver injury—right upper belly pain, loss of appetite, nausea, light-colored stool, dark yellow or brown urine, yellowing skin or eyes, unusual weakness or fatigue
- Redness, blistering, peeling, or loosening of the skin, including inside the mouth
- Severe diarrhea, fever
- Unusual vaginal discharge, itching, or odor
Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):
Pros and cons of Unasyn (ampicillin / sulbactam)
Pros
Treats many types of bacterial infections
Can use for fighting bacterial infections in children as young as 1 year of age
Available as a lower-cost generic
Cons
Typically needs to be given every 6 hours
Must be given as an IV or IM injection by a healthcare professional
Might not be a safe choice if you've had a severe allergy to penicillins
Pharmacist tips for Unasyn (ampicillin / sulbactam)
Make sure your healthcare team is aware of all the medications you're taking, especially if they include probenecid or allopurinol (Zyloprim). Taking either of these specific medications with Unasyn (ampicillin / sulbactam) can raise your risk for side effects.
Even though Unasyn (ampicillin / sulbactam) is given by injection, it can still cause diarrhea. But diarrhea should go away when you stop taking the antibiotic. Get medical help if you start having bloody diarrhea, fever, fatigue, or stomach cramps anytime during treatment or after stopping Unasyn (ampicillin / sulbactam). These can be signs of infectious diarrhea that needs to be treated right away.
Your healthcare provider might order blood tests to make sure you're not having side effects during your treatment with Unasyn (ampicillin / sulbactam). These tests help your care team check your liver health, kidney health, and blood cell counts.
Tell your care team if you develop other symptoms of an illness or if your symptoms become worse. You might need to be tested for an infection that might be caused by a virus or fungus and get appropriate treatment.
Frequently asked questions about Unasyn (ampicillin / sulbactam)
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What are the risks and warnings for Unasyn (ampicillin / sulbactam)?
Unasyn (ampicillin / sulbactam) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Allergic reactions
Risk factors: Allergy to penicillin or cephalosporins
Severe allergic reactions to Unasyn (ampicillin / sulbactam) are possible, including life-threatening reactions like facial swelling and anaphylaxis (e.g., closing of the throat). Let your care team know if you have an allergy to antibiotics. Get medical help right away if you notice hives, rash, red skin, swelling of the lips or tongue, or trouble breathing after you take Unasyn (ampicillin / sulbactam).
Severe skin reactions
Risk factors: Currently have a mononucleosis infection
Although rare, Unasyn (ampicillin / sulbactam) can cause severe skin reactions, such as Stevens-Johnson syndrome (SJS) and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome. Because a higher number of people with a mononucleosis infection who took ampicillin developed a skin rash, this medication isn't recommended if you currently have a mononucleosis infection. Get medical attention right away if you notice changes in your skin, such as rash, blisters, skin reddening, or skin peeling.
Liver problems
Risk factors: History of liver problems
Although rare, liver problems have been linked to Unasyn (ampicillin / sulbactam) use. Most times, liver damage from the medication can be reversible, but it can also sometimes be serious and life-threatening.
If you have a history of liver problems, you might need to get blood tests to check your liver health during treatment to make sure the medication continues to be safe for you. Get medical attention right away if you notice swelling of your stomach, stomach pain, yellowing of your skin or the whites of your eyes, stool changes (black or bloody stools), dark or brown urine, nausea, vomiting, or confusion. These can be signs of liver damage, and you might need to stop using the medication to prevent further damage.
Diarrhea from Clostridioides difficile infection
Unasyn (ampicillin / sulbactam) can raise your risk of getting infected with a bacteria called Clostridioides difficile (C. diff). Antibiotics change the amount of normal bacteria in your stomach and intestines. This can cause C. diff to overgrow in your gut and lead to an infection. C. diff infection can cause severe diarrhea.
It's important to recognize the difference between diarrhea as a side effect of Unasyn (ampicillin / sulbactam) and C. diff-related diarrhea. This type of infectious diarrhea can cause rapid heart rate, foul-smelling diarrhea, frequent bowel movements (even up to 15 times per day), fever, and nausea and it is a medical emergency. Get medical help right away if you have any of these symptoms so you can get tested for C. diff infection and get treatment.
Unasyn (ampicillin / sulbactam) dosage forms
Typical dosing for Unasyn (ampicillin / sulbactam)
Unasyn (ampicillin / sulbactam) is given as an injection into the veins (IV) or into the muscle (IM). The injection is usually administered by a healthcare professional in a healthcare setting (e.g., hospital, clinic, nursing home).
The dose and length of treatment depends on what type of infection you have and how serious it is. The prescriber will determine the right dose and length of treatment for you.
The total dose is expressed as the total grams of ampicillin and sulbactam added together. For most infections, the general dosage is as follows:
Adults and children weighing at least 88 lbs (40 kg): The typical dose is 1.5 grams to 3 grams given IV or IM every 6 hours.
Children ages 1 year and older: The typical dose is 300 mg/kg of body weight, given IV in equally divided doses every 6 hours.
The maximum dose is 3 grams given every 6 hours. Your dose might differ if you have kidney problems or if you're getting treated for certain resistant (difficult-to-treat) bacterial infections.
Unasyn (ampicillin / sulbactam) contraindications
Serious allergy to beta-lactam antibiotics (e.g., penicillins, cephalosporins)
History of having liver problems from using Unasyn (ampicillin / sulbactam)
What are alternatives to Unasyn (ampicillin / sulbactam)?
Skin infections (e.g., cellulitis)
Gynecological infections (e.g., vaginal, cervical, pelvic inflammatory disease)
Stomach infection in people ages 2 months and older
Pneumonia in people ages 2 months and older
Skin infection (e.g., cellulitis, foot infection due to diabetes) in adults
Pelvic infection in adult females
What is the latest news about Unasyn (ampicillin / sulbactam)?
Unasyn (ampicillin / sulbactam) images
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References
Best studies we foundBetrosian, A. P., et al. (2009). Ampicillin-sulbactam: An update on the use of parenteral and oral forms in bacterial infections. Expert Opinion on Drug Metabolism & Toxicology.
Bush, L. M., et al. (2023). Overview of anaerobic bacteria. Merck Manual Professional Version.
Bush, L. M. (2023). Pseudomonas infections. Merck Manual Consumer Version.
Centers for Disease Control and Prevention. (2021). Carbapenem-resistant Acinetobacter baumannii (CRAB): An urgent public health threat in United States healthcare facilities.
Gupta, K., et al. (2011). International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: A 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clinical Infectious Diseases.
Khanna, N. R., et al. (2022). Beta-lactamase inhibitors. StatPearls.
Lopez, N., et al. (2011). A comprehensive review of abdominal infections. World Journal of Emergency Surgery.
Pandey, N., et al. (2023). Beta-lactam antibiotics. StatPearls.
Peechakara, B. V., et al. (2024). Ampicillin/sulbactam. StatPearls.
Pfizer Inc. (2017). Unasyn® (ampicillin sodium/sulbactam sodium) [package insert].
Roerig. (2024). Unasyn - ampicillin sodium and sulbactam sodium injection, powder, for solution [package insert]. DailyMed.
ScienceDirect. (n.d.). Ampicillin/sulbactam.
Tamma, P. D., et al. (2022). Infectious Diseases Society of America 2023 guidance on the treatment of antimicrobial resistant gram-negative infections. Infectious Diseases Society of America.
Werth, B. J., et al. (2024). Overview of beta-lactams. Merck Manual Professional Version.
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