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Zosyn Injection

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Zosyn Injection

Zosyn Injection

Zosyn Injection Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Zosyn (piperacillin/tazobactam) for Injection is an antibiotic used to treat patients with moderate to severe bacterial infections. This medication is available in generic form. Common side effects include diarrhea, constipation, nausea, vomiting, stomach upset, fever, headache, insomnia, rash, and itching.

The usual total daily dose of Zosyn for adults is 3.375 g every six hours totaling 13.5 g (12.0 g piperacillin/1.5 g tazobactam). The usual duration of Zosyn treatment is from 7 to 10 days. Zosyn may interact with tobramycin, aminoglycosides, probenecid, oral anticoagulants, vecuronium, or methotrexate. Tell your doctor all medications and supplements you use. During pregnancy, Zosyn should be used only if prescribed. Piperacillin passes into breast milk in small amounts; tazobactam concentrations in human milk are unknown. Consult your doctor before breastfeeding.

Our Zosyn (piperacillin/tazobactam) for Injection Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Zosyn Injection FDA Prescribing Information: Side Effects
(Adverse Reactions)


Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

During the initial clinical investigations, 2621 patients worldwide were treated with ZOSYN in phase 3 trials. In the key North American monotherapy clinical trials (n=830 patients), 90% of the adverse events reported were mild to moderate in severity and transient in nature. However, in 3.2% of the patients treated worldwide, ZOSYN was discontinued because of adverse events primarily involving the skin (1.3%), including rash and pruritus; the gastrointestinal system (0.9%), including diarrhea, nausea, and vomiting; and allergic reactions (0.5%).

Table 3: Adverse Reactions from ZOSYN Monotherapy Clinical Trials System Organ Class

System Organ Class
Adverse Reaction
Gastrointestinal disorders
  Diarrhea (11.3%)
  Constipation (7.7%)
  Nausea (6.9%)
  Vomiting (3.3%)
  Dyspepsia (3.3%)
  Abdominal pain (1.3%)
  Pseudomembranous colitis ( ≤ 1%)
General disorders and administration site conditions
  Fever (2.4%)
  Injection site reaction ( ≤ 1%)
  Rigors ( ≤ 1%)
Immune system disorders
  Anaphylaxis ( ≤ 1%)
Infections and infestations
  Candidiasis (1.6%)
Metabolism and nutrition disorders
  Hypoglycemia ( ≤ 1%)
Musculoskeletal and connective tissue disorders
  Myalgia ( ≤ 1%)
  Arthralgia ( ≤ 1%)
Nervous system disorders
  Headache (7.7%)
  Insomnia (6.6%)
Skin and subcutaneous tissue disorders
  Rash (4.2%, including maculopapular, bullous, and urticarial)
  Pruritus (3.1%)
Vascular disorders
  Phlebitis (1.3%)
  Thrombophlebitis ( ≤ 1%)
  Hypotension ( ≤ 1%)
  Purpura ( ≤ 1%)
  Epistaxis ( ≤ 1%)
  Flushing ( ≤ 1%)

Nosocomial Pneumonia Trials

Two trials of nosocomial lower respiratory tract infections were conducted. In one study, 222 patients were treated with ZOSYN in a dosing regimen of 4.5 g every 6 hours in combination with an aminoglycoside and 215 patients were treated with imipenem/cilastatin (500 mg/500 mg q6h) in combination with an aminoglycoside. In this trial, treatment-emergent adverse events were reported by 402 patients, 204 (91.9%) in the piperacillin/tazobactam group and 198 (92.1%) in the imipenem/cilastatin group. Twenty-five (11.0%) patients in the piperacillin/tazobactam group and 14 (6.5%) in the imipenem/cilastatin group (p > 0.05) discontinued treatment due to an adverse event.

The second trial used a dosing regimen of 3.375 g given every 4 hours with an aminoglycoside.

Table 4: Adverse Reactions from ZOSYN Plus Aminoglycoside Clinical Trialsa

System Organ Class Adverse Reaction  
Blood and lymphatic system disorders
  Thrombocythemia (1.4%)
  Anemia ( ≤ 1%)
  Thrombocytopenia ( ≤ 1%)
  Eosinophilia ( ≤ 1%)
Gastrointestinal disorders
  Diarrhea (20%)
  Constipation (8.4%)
  Nausea (5.8%)
  Vomiting (2.7%)
  Dyspepsia (1.9%)
  Abdominal pain (1.8%)
  Stomatitis ( ≤ 1%)
General disorders and administration site conditions
  Fever (3.2%)
  Injection site reaction ( ≤ 1%)
Infections and infestations
  Oral candidiasis (3.9%)
  Candidiasis (1.8%)
  BUN increased (1.8%)
  Blood creatinine increased (1.8%)
  Liver function test abnormal (1.4%)
  Alkaline phosphatase increased ( ≤ 1%)
  Aspartate aminotransferase increased ( ≤ 1%)
  Alanine aminotransferase increased ( ≤ 1%)
Metabolism and nutrition disorders
  Hypoglycemia ( ≤ 1%)
  Hypokalemia ( ≤ 1%)
Nervous system disorders
  Headache (4.5%)
  Insomnia (4.5%)
Renal and urinary disorders
  Renal failure ( ≤ 1%)
Skin and subcutaneous tissue disorders
  Rash (3.9%)
  Pruritus (3.2%)
Vascular disorders
  Thrombophlebitis (1.3%)
  Hypotension (1.3%)
aFor adverse drug reactions that appeared in both studies the higher frequency is presented


Studies of ZOSYN in pediatric patients suggest a similar safety profile to that seen in adults. In a prospective, randomized, comparative, open-label clinical trial of pediatric patients with severe intra-abdominal infections (including appendicitis and/or peritonitis), 273 patients were treated with ZOSYN (112.5 mg/kg every 8 hours) and 269 patients were treated with cefotaxime (50 mg/kg) plus metronidazole (7.5 mg/kg) every 8 hours. In this trial, treatment-emergent adverse events were reported by 146 patients, 73 (26.7%) in the ZOSYN group and 73 (27.1%) in the cefotaxime/metronidazole group. Six patients (2.2%) in the ZOSYN group and 5 patients (1.9%) in the cefotaxime/metronidazole group discontinued due to an adverse event.

Adverse Laboratory Events (Seen During Clinical Trials)

Of the trials reported, including that of nosocomial lower respiratory tract infections in which a higher dose of ZOSYN was used in combination with an aminoglycoside, changes in laboratory parameters include:

Hematologic-decreases in hemoglobin and hematocrit, thrombocytopenia, increases in platelet count, eosinophilia, leukopenia, neutropenia. These patients were withdrawn from therapy; some had accompanying systemic symptoms (e.g., fever, rigors, chills).

Coagulation-positive direct Coombs' test, prolonged prothrombin time, prolonged partial thromboplastin time

Hepatic-transient elevations of AST (SGOT), ALT (SGPT), alkaline phosphatase, bilirubin

Renal-increases in serum creatinine, blood urea nitrogen

Additional laboratory events include abnormalities in electrolytes (i.e., increases and decreases in sodium, potassium, and calcium), hyperglycemia, decreases in total protein or albumin, blood glucose decreased, gamma-glutamyltransferase increased, hypokalemia, and bleeding time prolonged.

Post-Marketing Experience

In addition to the adverse drug reactions identified in clinical trials in Table 3 and Table 4, the following adverse reactions have been identified during postapproval use of ZOSYN.

Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish causal relationship to drug exposure.

Gastrointestinal-hepatitis, jaundice

Hematologic-hemolytic anemia, agranulocytosis, pancytopenia

Immune-hypersensitivity reactions, anaphylactic/anaphylactoid reactions (including shock)

Renal-interstitial nephritis

Skin and Appendages-erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis

Additional Experience with piperacillin

The following adverse reaction has also been reported for piperacillin for injection:

Skeletal-prolonged muscle relaxation [see DRUG INTERACTIONS].

Post-marketing experience with ZOSYN in pediatric patients suggests a similar safety profile to that seen in adults.

Read the entire FDA prescribing information for Zosyn Injection (Piperacillin and Tazobactam Pharmacy Bulk Vial) »


Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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