Ampicillin and Sulbactam Injection

Ampicillin and sulbactam injection treats bacterial infections caused by organisms that are susceptible to this antibiotic combination, including bacteria that produce enzymes (beta-lactamases) to resist standard penicillins.

• Skin and skin structure infections — caused by resistant strains of bacteria including Staphylococcus aureus, Escherichia coli, Klebsiella species, Proteus mirabilis, Bacteroides fragilis, Enterobacter species, and Acinetobacter calcoaceticus
• Intra-abdominal infections — caused by resistant E. coli, Klebsiella species, Bacteroides species (including B. fragilis), and Enterobacter species
• Gynecological infections — caused by resistant E. coli and Bacteroides species (including B. fragilis)
• Mixed infections involving both ampicillin-susceptible organisms and resistant bacteria may be treated with this combination without adding a second antibiotic
• For pediatric patients aged 1 year and older, Unasyn is given by intravenous infusion for these same types of infections; the IM route is not established in children

Ampicillin kills bacteria by interfering with the construction of their cell wall — a structure the bacteria need to survive. Without an intact wall, the bacteria break apart and die. Sulbactam doesn't do much killing on its own, but it plays a critical support role: it permanently disables beta-lactamases, the enzymes some bacteria produce to destroy ampicillin. By blocking those enzymes, sulbactam allows ampicillin to work against bacteria that would otherwise be resistant to it.

This combination gives the antibiotic a much broader reach — covering many gram-positive and gram-negative bacteria, including strains resistant to standard penicillins and cephalosporins.

Ampicillin and sulbactam injection is always given by a healthcare professional — never at home. It is administered either into a vein (IV) or into a muscle (IM) in adults.

• It is typically given every 6 hours, though kidney problems may require less frequent dosing (every 8, 12, or 24 hours)
• IV doses can be given as a slow injection or as a longer infusion, depending on the clinical situation
• In pediatric patients 1 year or older, it is given only by IV infusion, in divided doses every 6 hours; IV treatment in children should generally not exceed 14 days
• Children weighing 40 kg or more are dosed like adults

Always follow your prescriber's exact instructions. Do not adjust the schedule without checking with your care team first.

Most people tolerate ampicillin and sulbactam injection well. The most commonly reported side effects include:

• Pain at the injection site (more common with IM injection)
• Diarrhea
• Rash
• Nausea or vomiting
• Itching
• Headache
• Vein irritation or inflammation (thrombophlebitis) at the IV site
• Fatigue or feeling unwell

More serious reactions — including severe allergic reactions, life-threatening skin conditions, liver problems, and C. difficile diarrhea — can occur and require immediate medical attention. Tell your care team about any new symptoms right away.

• Severe allergic reactions: Life-threatening anaphylaxis (a sudden, whole-body allergic reaction) has been reported. People with a history of penicillin or cephalosporin allergy are at higher risk. Emergency treatment must be available.
• Serious skin reactions: Rare but potentially fatal skin conditions including Stevens-Johnson syndrome, toxic epidermal necrolysis (TEN), and DRESS syndrome have occurred. Any new rash during treatment must be evaluated promptly — if it progresses, the drug must be stopped.
• Liver toxicity: Hepatitis and cholestatic jaundice (liver inflammation that impairs bile flow) have been reported, rarely with fatal outcomes. Patients with liver disease should have their liver function monitored regularly during treatment.
• Clostridioides difficile (C. difficile) infection: Like all antibiotics, this medication can disrupt normal gut bacteria and allow C. difficile to overgrow, causing severe diarrhea or colitis. This can occur during treatment or up to two months afterward.
• Antibiotic resistance: This medication should only be used for proven or strongly suspected bacterial infections to help prevent the development of resistant bacteria.

Ampicillin and sulbactam injection can interact with a few other medications. Be sure your care team knows everything you take:

• Probenecid (used for gout) — slows the kidneys' removal of ampicillin and sulbactam, increasing and prolonging blood levels of both drugs
• Allopurinol (used for gout or high uric acid) — substantially increases the risk of developing a skin rash when taken at the same time as ampicillin
• Aminoglycoside antibiotics (such as gentamicin or tobramycin) — must never be mixed in the same IV bag or syringe as ampicillin and sulbactam, because the ampicillin component can inactivate the aminoglycoside

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Do not use this medication if you have ever had a serious allergic reaction — such as anaphylaxis or Stevens-Johnson syndrome — to penicillins, cephalosporins, or other beta-lactam antibiotics
• Do not use this medication if you have previously developed jaundice or liver problems specifically linked to ampicillin and sulbactam
• Tell your doctor about any past antibiotic allergies or reactions to multiple allergens before starting treatment
• Tell your doctor if you have kidney disease — the dosing schedule will need to be adjusted based on how well your kidneys work
• Tell your doctor if you have liver disease — liver function should be checked regularly during treatment
• Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding
• In children aged 1 year and older, the IV route is used; the IM route has not been shown to be safe and effective in pediatric patients

Taking too much of this medication can cause neurological side effects, including seizures (convulsions), especially if high levels build up in the fluid around the brain and spinal cord. If an overdose is suspected, seek emergency medical care immediately. The label notes that ampicillin — and likely sulbactam — can be partially removed from the blood by hemodialysis (a kidney-filtering procedure).

Ampicillin and sulbactam injection works by killing susceptible bacteria during their active growth phase — it disrupts the construction of the bacterial cell wall, which is essential for bacterial survival. Sulbactam permanently disables the beta-lactamase enzymes that would otherwise break down ampicillin, extending the antibiotic's reach to bacteria that carry resistance. The result is a broad-spectrum antibacterial effect covering many gram-positive and gram-negative bacteria, including resistant strains.

When given as a 15-minute IV infusion, peak blood levels of both ampicillin and sulbactam are reached immediately after the infusion is complete. After an IM injection, drug levels in the blood are lower but still therapeutic. Both drugs have a short half-life of about 1 hour in people with normal kidney function, meaning they are cleared fairly quickly. Approximately 75–85% of both drugs are eliminated unchanged through the urine within the first 8 hours, so kidney function has a direct impact on how long the drugs stay in the body and how often they need to be given.

stored at 20° to 25°C (68° to 77°F) prior to reconstitution.