6 ADVERSE REACTIONS The most common adverse reactions (incidence >5%) are diarrhea, constipation, nausea, headache and insomnia. (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer Inc. at 1-800-438-1985 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 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 Adverse Reaction Gastrointestinal disorders Diarrhea (11.3%) Constipation (7.7%) Nausea (6.9%) Vomiting (3.3%) Dyspepsia (3.3%) Abdominal pain (1.3%) 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%) Pseudomembranous colitis (≤1%) Metabolism and nutrition disorders Hypoglycemia (≤1%) Musculoskeletal and connective tissue disorders Myalgia(≤1%) Arthralgia (≤1%) Nervous system disorders Headache (7.7%) Psychiatric disorders Insomnia (6.6%) Skin and subcutaneous tissue disorders Rash (4.2%, including maculopapular, bullous, and urticarial) Pruritus (3.1%) Purpura (≤1%) Vascular disorders Phlebitis (1.3%) Thrombophlebitis (≤1%) Hypotension (≤1%) Flushing (≤1%) Respiratory, thoracic and mediastinal disorders Epistaxis (≤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 TrialsFor adverse drug reactions that appeared in both studies the higher frequency is presented. 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%) Investigations 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%) Psychiatric disorders 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%) Other trials: Nephrotoxicity In a randomized, multicenter, controlled trial in 1200 adult critically ill patients, piperacillin/tazobactam was found to be a risk factor for renal failure (odds ratio 1.7, 95% CI 1.18 to 2.43), and associated with delayed recovery of renal function as compared to other beta-lactam antibacterial drugs1[see Warnings and Precautions (5.5) ]. Pediatrics 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. 6.2 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 post-approval 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 a causal relationship to drug exposure. Hepatobiliary—hepatitis, jaundice Hematologic—hemolytic anemia, agranulocytosis, pancytopenia Immune—hypersensitivity reactions, anaphylactic/anaphylactoid reactions (including shock) Renal—interstitial nephritis Respiratory—eosinophilic pneumonia Skin and Appendages—erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis (AGEP), dermatitis exfoliative 6.3 Additional Experience with piperacillin The following adverse reaction has also been reported for piperacillin for injection: Skeletal—prolonged muscle relaxation [see Drug Interactions (7.5) ]. Post-marketing experience with ZOSYN in pediatric patients suggests a similar safety profile to that seen in adults.