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Unasyn Side Effects

Generic name: ampicillin / sulbactam

Medically reviewed by Last updated on Nov 16, 2023.

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

Applies to ampicillin / sulbactam: injection powder for solution.

Serious side effects of Unasyn

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


Incidence not known

Other side effects of Unasyn

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


Incidence not known

For Healthcare Professionals

Applies to ampicillin / sulbactam: injectable powder for injection.


This drug was generally well-tolerated.[Ref]


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[Ref]


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[Ref]


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[Ref]


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[Ref]


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[Ref]

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

Nervous system

Uncommon (0.1% to 1%): Headache

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

Postmarketing reports: Convulsion[Ref]

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.[Ref]


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

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


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


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

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


Frequency not reported: Increased BUN, increased creatinine

Postmarketing reports: Tubulointerstitial nephritis[Ref]


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


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


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3. Ramakrishnan K, Scheid DC (2005) "Diagnosis and management of acute pyelonephritis in adults." Am Fam Physician, 71, p. 933-42

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11. Konstantinidis AB, Markopoulos A, Trigonides G (1985) "Ampicillin induced erythema multiforme." J Oral Med, 40, p. 168-70

12. Mehta D, Warwick GL, Goldberg MJ (1986) "QT prolongation after ampicillin anaphylaxis." Br Heart J, 55, p. 308-10

13. Dolovich J, Ruhno J, Sauder DN, Ahlstedt S, Hargreave FE (1988) "Isolated late cutaneous skin test response to ampicillin: a distinct entity." J Allergy Clin Immunol, 82, p. 676-9

14. Hodak E, Ben-Shetrit A, Ingber A, Sandbank M (1990) "Bullous pemphigoid: an adverse effect of ampicillin." Clin Exp Dermatol, 15, p. 50-2

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16. Johnson JR, Lyons MF, Pearce W, et al. (1991) "Therapy for women hospitalized with acute pyelonephritis: a randomized trial of ampicillin versus trimethoprim-sulfamethoxasole for 14 days." J Infect Dis, 163, p. 325-30

17. Cavanzo FJ, Garcia CF, Botero RC (1990) "Chronic cholestasis, paucity of bile ducts, red cell aplasia, and the Stevens-Johnson syndrome." Gastroenterology, 99, p. 854-6

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19. Shimanovich I, Rose C, Sitaru C, Brocker EB, Zillikens D (2004) "Localized linear IgA disease induced by ampicillin / sulbactam." J Am Acad Dermatol, 51(1 Pt 1), p. 95-8

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25. Koklu S, Koksal AS, Asil M, Kiyici H, Coban S, Arhan M (2004) "Probable sulbactam/ampicillin-associated prolonged cholestasis." Ann Pharmacother, 38, p. 2055-8

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.