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Overview: Ampicillin/sulbactam is an antibiotic that is injected into a blood vessel or muscle. It is used to treat bacterial infections. It kills certain bacteria by preventing them from being able to create their cell wall. Common side effects include diarrhea, rash, or pain, itching, swelling, or redness near the injection site. Serious side effects may include severe diarrhea, severe skin reactions, or allergic reactions.

Uses

What is ampicillin/sulbactam used for?

Ampicillin/sulbactam is an antibiotic that is commonly used for infections caused by certain bacteria.

Ampicillin/sulbactam may not be appropriate for all infections, depending on which germs are causing the infection. Some bacteria may have developed resistance to ampicillin/sulbactam, which will make it not work as well. 

Ampicillin/sulbactam only treats certain infections caused by bacteria. It will not work for infections caused by viruses, such as the common cold, the flu, or coronavirus. It also will not work for any other infections that are not caused by bacteria. Using ampicillin/sulbactam or any other antibiotic when it is not needed may cause the antibiotic to not work for bacterial infections in the future.

Ampicillin/sulbactam may also be used for other conditions as determined by your healthcare provider.

How does ampicillin/sulbactam work (mechanism of action)?

Ampicillin kills certain bacteria by preventing them from being able to create their cell wall. Some bacteria can produce substances that reduce the effects of ampicillin. Sulbactam destroys these substances, allowing ampicillin to keep working.

How is ampicillin/sulbactam supplied (dosage forms)?

Brands and other names

  • Unasyn

Ampicillin/sulbactam is available in injectable forms.

How should I store ampicillin/sulbactam?

Ampicillin/sulbactam is usually given by a healthcare provider in a hospital or clinic. If you will store ampicillin/sulbactam at home, follow the instructions given by your healthcare provider.

Side Effects

What are the most common side effects of ampicillin/sulbactam?

The most common side effects of ampicillin/sulbactam are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Pain, itching, swelling, or redness near the injection site
  • Diarrhea
  • Skin rash

There may be other side effects of ampicillin/sulbactam that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of ampicillin/sulbactam?

While less common, the most serious side effects of ampicillin/sulbactam are described below, along with what to do if they happen.

Severe Allergic Reactions. Ampicillin/sulbactam can cause allergic reactions, including a specific type of allergic reaction called DRESS. DRESS stands for Drug Reaction with Eosinophilia and Systemic Symptoms. It is also sometimes called multiorgan hypersensitivity. This is a reaction that can affect multiple parts of the body, including your liver, kidneys, and heart. Stop using the medicine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Severe Skin Reactions. Ampicillin/sulbactam can cause severe skin reactions, called Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP), which can lead to death if not treated. If you develop a rash, stop ampicillin/sulbactam and tell your healthcare provider right away. Get emergency help if you have any of the following symptoms of SJS, TEN, or AGEP.

  • Painful red or purple skin that looks burned and peels off
  • Red skin covered with fluid-filled bumps (pustules)
  • Flat red rash or blisters on your skin, mouth, nose, and genitals
  • Red, painful, watery eyes

Antibiotic-associated Diarrhea. An overgrowth of germs called Clostridioides difficile, or “C. diff,” can happen in your gut with many types of antibiotics, including ampicillin/sulbactam. This can cause a condition known as antibiotic-associated diarrhea or pseudomembranous colitis, and can happen even up to two months after stopping the antibiotic. Call your healthcare provider right away if you have any of the following symptoms of this condition.

  • Watery diarrhea
  • Diarrhea that does not go away
  • Blood in your stool (poop)
  • Severe stomach cramps
  • Fever that starts after you start or finish the medicine

Blood Disorders. Ampicillin/sulbactam can cause blood disorders, such as agranulocytosis, hemolytic anemia, and low platelet levels (thrombocytopenia). Stop using ampicillin/sulbactam and get help right away if you have any of the following symptoms of blood disorders.

  • Fever that does not go away
  • Shortness of breath
  • Pale or yellowish skin
  • Easy bruising or bleeding
  • Frequent infection
  • Unusual weakness or tiredness
  • Dizziness, lightheadedness, or feeling like you are about to pass out
  • Headache
  • Fast or abnormal heartbeat

Liver Damage. Liver damage, also called hepatotoxicity or hepatic dysfunction, can happen when using ampicillin/sulbactam. Call your healthcare provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Warnings & Precautions

Who should not use ampicillin/sulbactam?

Allergies to Ingredients. People who are allergic to any of the following should not use ampicillin/sulbactam.

  • Ampicillin
  • Unasyn
  • Sulbactam
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific ampicillin/sulbactam products they stock.

Allergies to Certain Antibiotics. Some people who have an allergy to certain other antibiotics, such as penicillin, may also be allergic to ampicillin/sulbactam. Let your healthcare provider know if you have ever had a severe allergic reaction to an antibiotic.

Liver Damage from Ampicillin/Sulbactam. In rare cases, ampicillin/sulbactam can cause liver damage. If this has happened to you in the past, you should not use ampicillin/sulbactam again.

What should I know about ampicillin/sulbactam before using it?

Ampicillin/sulbactam is usually given by a healthcare provider in a hospital or clinic.

If you will store ampicillin/sulbactam at home, do not share it with other people, even if they have the same condition as you. It may harm them. Keep ampicillin/sulbactam out of the reach of children.

What should I tell my healthcare provider before using ampicillin/sulbactam?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if ampicillin/sulbactam is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

  • An allergy to penicillin or any other medicines
  • History of antibiotic-associated diarrhea
  • Kidney problems
  • Liver problems
  • Mononucleosis, also called “mono” or the kissing disease

Other Medicines and Supplements. Ampicillin/sulbactam may interact with other medicines and supplements. Before using ampicillin/sulbactam, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how ampicillin/sulbactam could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant. Your healthcare provider will advise you if you should use ampicillin/sulbactam while you are pregnant or trying to get pregnant.

Breastfeeding. Ampicillin/sulbactam passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should use ampicillin/sulbactam while breastfeeding.

Interactions

Does ampicillin/sulbactam interact with foods or drinks?

There are no known interactions between ampicillin/sulbactam and foods or drinks.

It is unknown if drinking alcohol will affect ampicillin/sulbactam, but heavy drinking can slow your immune response and make it harder for your body to fight infection.

Does ampicillin/sulbactam interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using ampicillin/sulbactam.

  • Allopurinol or probenecid, which is a medicine commonly used for gout

This may not be a complete list of medicines that can interact with ampicillin/sulbactam. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much ampicillin/sulbactam?

If you or someone else has used too much ampicillin/sulbactam, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of ampicillin/sulbactam?

Ampicillin/sulbactam is usually given by a healthcare provider in a hospital or clinic. Your healthcare provider will make sure you are receiving ampicillin/sulbactam as scheduled.

It is important to complete your prescribed course of ampicillin/sulbactam, even if your symptoms get better or go away. This will reduce the risk that future infections are resistant to ampicillin/sulbactam or other similar medicines.