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Generic Name: ampicillin and sulbactam (am pi SIL in and sul BAK tam)
Brand Name: Unasyn
Physician reviewed Unasyn patient information - includes Unasyn description, dosage and directions.
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Drug Information:
Unasyn are penicillin antibiotics that fight bacteria. Unasyn is a combination medicine used to treat many different types of infections caused by bacteria. Unasyn may also be used for purposes not listed in this medication guide. You should not use Unasyn if you have ever had a severe allergic reaction to any type of penicillin or cephalosporin antibiotic, or if you have had liver problems while using Unasyn. You should not use this medicine if you are allergic to ampicillin or sulbactam, or if you have ever had Learn more

Unasyn Side Effects

Unasyn Side Effects

Note: This document contains side effect information about ampicillin / sulbactam. Some of the dosage forms listed on this page may not apply to the brand name Unasyn.

For the Consumer

Applies to ampicillin / sulbactam: injection powder for solution

Along with its needed effects, ampicillin/sulbactam may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking ampicillin / sulbactam:

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 the 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 side effects of ampicillin / sulbactam may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions 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


This drug was generally well-tolerated.


Very common (10% or more): Pain at IM injection site (16%)

Common (1% to 10%): Pain at IV injection site, thrombophlebitis, phlebitis

Postmarketing reports: Injections site reaction


Common (1% to 10%): Diarrhea

Uncommon (0.1% to 1%): Nausea, vomiting, flatulence, abdominal distension, glossitis

Frequency not reported: Pancreatitis, enterocolitis, pseudomembranous colitis

Postmarketing reports: Gastritis, stomatitis, black "hairy" tongue, Clostridium difficile associated diarrhea


Frequency not reported: Hypersensitivity reactions to ampicillin (including urticarial rash, edema, hypotension, fever, eosinophilia, dyspnea, delayed hypersensitivity maculopapular rash, anaphylaxis, interstitial nephritis, Henoch-Schonlein purpura, focal glomerulonephritis, Stevens-Johnson syndrome)

Postmarketing reports: Serious and fatal hypersensitivity (anaphylactic) reactions


Common (1% to 10%): Rash

Uncommon (0.1% to 1%): Itching, facial swelling, erythema

Frequency not reported: Ampicillin-associated bullous pemphigoid, linear IgA dermatosis, pseudoporphyria

Postmarketing reports: Erythema multiforme, toxic epidermal necrolysis, Stevens-Johnson syndrome, acute generalized exanthematous pustulosis, urticaria, exfoliative dermatitis


Hemolytic anemia, thrombocytopenic purpura, and agranulocytosis were generally reversible when therapy was discontinued; may be hypersensitivity events.

Frequency not reported: Decreased hemoglobin, decreased hematocrit, decreased red blood cells, decreased white blood cells, decreased neutrophils, decreased lymphocytes, decreased platelets, increased lymphocytes, increased monocytes, increased basophils, increased eosinophils, increased platelets, thrombocytopenia, leukopenia, red cell aplasia, anemia, atypical lymphocytosis

Postmarketing reports: Hemolytic anemia, thrombocytopenic purpura, agranulocytosis, positive direct Coombs test

Nervous system

Uncommon (0.1% to 1%): Headache

Frequency not reported: Seizures, neurotoxic potential, worsening myasthenia gravis symptoms

Postmarketing reports: Convulsion

Seizures have been reported in very ill patients with high serum levels of ampicillin. High cerebral spinal fluid (CSF) levels of some penicillins are potentially neurotoxic; the CSF levels of ampicillin rise significantly in meningitis.


Frequency not reported: Increased AST, increased ALT, hepatitis, prolonged cholestasis

Postmarketing reports: Cholestatic hepatitis, cholestasis, hyperbilirubinemia, jaundice, abnormal hepatic function


Frequency not reported: Increased alkaline phosphatase, increased lactate dehydrogenase, decreased serum albumin, decreased total protein


Uncommon (0.1% to 1%): Urine retention, dysuria

Frequency not reported: Urinary red blood cells, urinary hyaline casts


Frequency not reported: Increased BUN, increased creatinine

Postmarketing reports: Tubulointerstitial nephritis


Uncommon (0.1% to 1%): Candidiasis, fatigue, malaise, chest pain, edema, chills, substernal pain, mucosal bleeding


Uncommon (0.1% to 1%): Throat tightness, epistaxis

Editorial References and Review

Medically reviewed by BestRx Medical Team Last updated on 1/1/2020.

Source: Drugs.com Unasyn