Unasyn Side Effects

Generic Name: ampicillin / sulbactam

Note: This page contains side effects data for the generic drug ampicillin / sulbactam. It is possible that some of the dosage forms included below may not apply to the brand name Unasyn.

It is possible that some side effects of Unasyn may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to ampicillin / sulbactam: injection powder for solution

As well as its needed effects, ampicillin / sulbactam may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking ampicillin / sulbactam, check with your doctor or nurse immediately:

Less common
  • Changes in skin color
  • diarrhea
  • pain, tenderness, or swelling of the foot or leg
  • Bloody nose
  • burning while urinating
  • chest pain, discomfort, or pressure
  • chills
  • decrease in frequency of urination
  • decrease in urine volume
  • difficulty in passing urine (dribbling)
  • flushing or redness of the skin
  • painful urination
  • swelling
  • swelling or puffiness of the face
  • tightness in the throat
  • unusually warm skin
Incidence not known
  • Abdominal or stomach cramps or tenderness
  • black, hairy tongue
  • blistering, peeling, or loosening of the skin
  • bloating
  • cough or hoarseness
  • cracks in the skin
  • diarrhea, watery and severe, which may also be bloody
  • fever
  • fever with or without chills
  • general feeling of tiredness or weakness
  • increased thirst
  • itching
  • joint or muscle pain
  • loss of heat from the body
  • lower back or side pain
  • nausea or vomiting
  • pain
  • red, irritated eyes
  • red, swollen skin
  • scaly skin
  • severe stomach pain
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • swelling or inflammation of the mouth
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • unusual weight loss
  • vomiting

Some ampicillin / sulbactam side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common
  • Bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site
  • Excess air or gas in the stomach or intestines
  • full or bloated feeling
  • general feeling of discomfort or illness
  • headache
  • passing gas
  • pressure in the stomach
  • redness, swelling, or soreness of the tongue
  • swelling of the abdominal or stomach area
  • white patches in the mouth or throat or on the tongue
  • white patches with diaper rash
Incidence not known
  • Burning feeling in the chest or stomach
  • indigestion
  • stomach upset

For Healthcare Professionals

Applies to ampicillin / sulbactam: injectable powder for injection


Ampicillin-sulbactam is generally well-tolerated.


Local side effects have included pain at the intramuscular injection site (16%), pain at the intravenous injection site (3%), and thrombophlebitis (3%).


Gastrointestinal side effects have included diarrhea (3%), nausea (<1%), vomiting (<1%), flatulence (<1%), abdominal distension (<1%), and glossitis (<1%). Rare cases of pancreatitis have been reported. Ampicillin-class antibiotics have been associated with gastritis, stomatitis, black hairy tongue, enterocolitis, and pseudomembranous colitis.


Hypersensitivity reactions to ampicillin have included urticarial rash, edema, hypotension, fever, eosinophilia, dyspnea, a delayed hypersensitivity maculopapular rash, anaphylaxis, interstitial nephritis, Henoch-Schonlein purpura, focal glomerulonephritis, and Stevens-Johnson syndrome.


Dermatologic side effects have included rash (<2%), itching (<1%), erythema multiforme, and exfoliative dermatitis. Rare cases of ampicillin-associated bullous pemphigoid, linear IgA dermatosis, and pseudoporphyria have been reported.


Hematologic side effects have included decreases in hemoglobin, hematocrit, red blood cells, neutrophils, lymphocytes, and platelets, and increases in lymphocytes, monocytes, basophils, eosinophils, and platelets. Thrombocytopenia, leukopenia, red cell aplasia, anemia, and positive direct Coombs test have rarely been reported. Atypical lymphocytosis has been reported in a pediatric patient. Penicillins have been associated with agranulocytosis.

Nervous system

Nervous system side effects have included seizures in very ill patients with high serum concentrations of ampicillin. High cerebral spinal fluid (CSF) levels of some penicillins are known to be potentially neurotoxic, and the CSF concentrations of ampicillin rise significantly in meningitis. Ampicillin may worsen myasthenia gravis symptoms.


Hepatic side effects have included increases in AST (SGOT), ALT (SGPT), alkaline phosphatase, and LDH. Rare cases of hepatitis and prolonged cholestasis have been reported.


Metabolic side effects have included decreases in serum albumin and total protein.


Genitourinary side effects have included urine retention, dysuria, urinary red blood cells, and urinary hyaline casts. Superinfections may occur (i.e., Candida, Pseudomonas).


Renal side effects have included increases in BUN and creatinine.


Other side effects have included facial swelling, erythema, chills, throat tightness, substernal pain, epistaxis, and mucosal bleeding.

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