Generic Name: piperacillin sodium and tazobactam sodium
Dosage Form: injection, powder, lyophilized, for solution
Zosyn®
(Piperacillin and Tazobactam for Injection, USP)
To reduce the development of drug-resistant bacteria and maintain the effectiveness of Zosyn® (piperacillin and tazobactam) injection and other antibacterial drugs, Zosyn (piperacillin and tazobactam) should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.
DESCRIPTION
Zosyn (piperacillin and tazobactam for injection, USP) is an injectable antibacterial combination product consisting of the semisynthetic antibiotic piperacillin sodium and the β-lactamase inhibitor tazobactam sodium for intravenous administration.
Piperacillin sodium is derived from D(-)-α-aminobenzyl-penicillin. The chemical name of piperacillin sodium is sodium (2S,5R,6R) - 6 - [(R) - 2 - (4 - ethyl - 2,3 - dioxo - 1 - piperazine - carboxamido) - 2 - phenylacetamido] - 3,3 - dimethyl - 7 - oxo - 4 - thia - 1 - azabicyclo[3.2.0]heptane - 2 - carboxylate. The chemical formula is C23H26N5NaO7S and the molecular weight is 539.5. The chemical structure of piperacillin sodium is:
Tazobactam sodium, a derivative of the penicillin nucleus, is a penicillanic acid sulfone. Its chemical name is sodium (2S,3S,5R) - 3 - methyl - 7 - oxo - 3 - (1H - 1,2,3 - triazol - 1 - ylmethyl) - 4 - thia - 1 - azabicyclo[3.2.0]heptane - 2 - carboxylate - 4,4 - dioxide. The chemical formula is C10H11N4NaO5S and the molecular weight is 322.3. The chemical structure of tazobactam sodium is:
Zosyn, piperacillin/tazobactam parenteral combination, is a white to off-white sterile, cryodesiccated powder consisting of piperacillin and tazobactam as their sodium salts packaged in glass vials. The formulation also contains edetate disodium dihydrate (EDTA) and sodium citrate.
Each Zosyn 2.25 g single dose vial contains an amount of drug sufficient for withdrawal of piperacillin sodium equivalent to 2 grams of piperacillin and tazobactam sodium equivalent to 0.25 g of tazobactam. The product also contains 0.5 mg of EDTA per vial.
Each Zosyn 3.375 g single dose vial contains an amount of drug sufficient for withdrawal of piperacillin sodium equivalent to 3 grams of piperacillin and tazobactam sodium equivalent to 0.375 g of tazobactam. The product also contains 0.75 mg of EDTA per vial.
Each Zosyn 4.5 g single dose vial contains an amount of drug sufficient for withdrawal of piperacillin sodium equivalent to 4 grams of piperacillin and tazobactam sodium equivalent to 0.5 g of tazobactam. The product also contains 1 mg of EDTA per vial.
Zosyn (piperacillin and tazobactam for injection, USP) contains a total of 2.79 mEq (64 mg) of sodium (Na+) per gram of piperacillin in the combination product.
CLINICAL PHARMACOLOGY
Adults
Peak plasma concentrations of piperacillin and tazobactam are attained immediately after completion of an intravenous infusion of Zosyn. Piperacillin plasma concentrations, following a 30-minute infusion of Zosyn, were similar to those attained when equivalent doses of piperacillin were administered alone, with mean peak plasma concentrations of approximately 134, 242, and 298 μg/mL for the 2.25 g, 3.375 g, and 4.5 g Zosyn (piperacillin/tazobactam) doses, respectively. The corresponding mean peak plasma concentrations of tazobactam were 15, 24, and 34 μg/mL, respectively.
Following a 30-minute I.V. infusion of 3.375 g Zosyn every 6 hours, steady-state plasma concentrations of piperacillin and tazobactam were similar to those attained after the first dose. In like manner, steady-state plasma concentrations were not different from those attained after the first dose when 2.25 g or 4.5 g doses of Zosyn were administered via 30-minute infusions every 6 hours. Steady-state plasma concentrations after 30-minute infusions every 6 hours are provided in Table 1.
Following single or multiple Zosyn doses to healthy subjects, the plasma half-life of piperacillin and of tazobactam ranged from 0.7 to 1.2 hours and was unaffected by dose or duration of infusion.
Piperacillin is metabolized to a minor microbiologically active desethyl metabolite. Tazobactam is metabolized to a single metabolite that lacks pharmacological and antibacterial activities. Both piperacillin and tazobactam are eliminated via the kidney by glomerular filtration and tubular secretion. Piperacillin is excreted rapidly as unchanged drug with 68% of the administered dose excreted in the urine. Tazobactam and its metabolite are eliminated primarily by renal excretion with 80% of the administered dose excreted as unchanged drug and the remainder as the single metabolite. Piperacillin, tazobactam, and desethyl piperacillin are also secreted into the bile.
Both piperacillin and tazobactam are approximately 30% bound to plasma proteins. The protein binding of either piperacillin or tazobactam is unaffected by the presence of the other compound. Protein binding of the tazobactam metabolite is negligible.
Piperacillin and tazobactam are widely distributed into tissues and body fluids including intestinal mucosa, gallbladder, lung, female reproductive tissues (uterus, ovary, and fallopian tube), interstitial fluid, and bile. Mean tissue concentrations are generally 50% to 100% of those in plasma. Distribution of piperacillin and tazobactam into cerebrospinal fluid is low in subjects with non-inflamed meninges, as with other penicillins.
After the administration of single doses of piperacillin/tazobactam to subjects with renal impairment, the half-life of piperacillin and of tazobactam increases with decreasing creatinine clearance. At creatinine clearance below 20 mL/min, the increase in half-life is twofold for piperacillin and fourfold for tazobactam compared to subjects with normal renal function. Dosage adjustments for Zosyn are recommended when creatinine clearance is below 40 mL/min in patients receiving the usual recommended daily dose of Zosyn (piperacillin and tazobactam for injection, USP). (See DOSAGE AND ADMINISTRATION section for specific recommendations for the treatment of patients with renal insufficiency.)
Hemodialysis removes 30% to 40% of a piperacillin/tazobactam dose with an additional 5% of the tazobactam dose removed as the tazobactam metabolite. Peritoneal dialysis removes approximately 6% and 21% of the piperacillin and tazobactam doses, respectively, with up to 16% of the tazobactam dose removed as the tazobactam metabolite. For dosage recommendations for patients undergoing hemodialysis, see DOSAGE AND ADMINISTRATION section.
The half-life of piperacillin and of tazobactam increases by approximately 25% and 18%, respectively, in patients with hepatic cirrhosis compared to healthy subjects. However, this difference does not warrant dosage adjustment of Zosyn due to hepatic cirrhosis.
Pediatrics
Piperacillin and tazobactam pharmacokinetics were studied in pediatric patients 2 months of age and older. The clearance of both compounds is slower in the younger patients compared to older children and adults.
In a population PK analysis, estimated clearance for 9 month-old to 12 year-old patients was comparable to adults, with a population mean (SE) value of 5.64 (0.34) mL/min/kg. The piperacillin clearance estimate is 80% of this value for pediatric patients 2 - 9 months old. In patients younger than 2 months of age, clearance of piperacillin is slower compared to older children; however, it is not adequately characterized for dosing recommendations. The population mean (SE) for piperacillin distribution volume is 0.243 (0.011) L/kg and is independent of age.
Microbiology
Piperacillin sodium exerts bactericidal activity by inhibiting septum formation and cell wall synthesis of susceptible bacteria. In vitro, piperacillin is active against a variety of gram-positive and gram-negative aerobic and anaerobic bacteria. Tazobactam sodium has little clinically relevant in vitro activity against bacteria due to its reduced affinity to penicillin-binding proteins. It is, however, a β-lactamase inhibitor of the Richmond-Sykes class III (Bush class 2b & 2b') penicillinases and cephalosporinases. It varies in its ability to inhibit class II and IV (2a & 4) penicillinases. Tazobactam does not induce chromosomally-mediated β-lactamases at tazobactam concentrations achieved with the recommended dosage regimen.
Piperacillin/tazobactam has been shown to be active against most strains of the following microorganisms both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section.
Aerobic and facultative gram-positive microorganisms:
Staphylococcus aureus (excluding methicillin and oxacillin-resistant isolates)
Aerobic and facultative gram-negative microorganisms:
Haemophilus influenzae (excluding β-lactamase negative, ampicillin-resistant isolates)
Pseudomonas aeruginosa (given in combination with an aminoglycoside to which the isolate is susceptible)
Gram-negative anaerobes:
Bacteroides fragilis group (B. fragilis, B. ovatus, B. thetaiotaomicron, and B. vulgatus)
The following in vitro data are available, but their clinical significance is unknown.
At least 90% of the following microorganisms exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for piperacillin/tazobactam. However, the safety and effectiveness of piperacillin/tazobactam in treating clinical infections due to these bacteria have not been established in adequate and well-controlled clinical trials.
Aerobic and facultative gram-positive microorganisms:
Enterococcus faecalis (ampicillin or penicillin-susceptible isolates only)
Staphylococcus epidermidis (excluding methicillin and oxacillin-resistant isolates)
Streptococcus pneumoniae† (penicillin-susceptible isolates only)
Aerobic and facultative gram-negative microorganisms:
Gram-positive anaerobes:
Gram-negative anaerobes:
† These are not β-lactamase producing bacteria and, therefore, are susceptible to piperacillin alone.
Susceptibility Testing Methods
As is recommended with all antimicrobials, the results of in vitro susceptibility tests, when available, should be provided to the physician as periodic reports, which describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting the most effective antimicrobial.
Dilution Techniques:
Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized procedure. Standardized procedures are based on a dilution method (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of piperacillin and tazobactam powders.1,2 MIC values should be determined using serial dilutions of piperacillin combined with a fixed concentration of 4 μg/mL tazobactam. The MIC values obtained should be interpreted according to criteria provided in Table 2.
Diffusion Technique:
Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure1,3 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 100 μg of piperacillin and 10 μg of tazobactam to test the susceptibility of microorganisms to piperacillin/tazobactam. The disk diffusion interpreted criteria are provided in Table 2.
Anaerobic Techniques
For anaerobic bacteria, the susceptibility to piperacillin/tazobactam can be determined by the reference agar dilution method.4
| Susceptibility Test Result Interpretive Criteria | ||||||
|---|---|---|---|---|---|---|
| Minimal Inhibitory Concentration (MIC in μg/mL) | Disk Diffusion (Zone Diameter in mm) | |||||
| Pathogen | S | I | R | S | I | R |
| a These interpretive criteria for Haemophilus influenzae are applicable only to tests performed using Haemophilus Test Medium inoculated with a direct colony suspension and incubated at 35°C in ambient air for 20 to 24 hours. | ||||||
| Enterobacteriaceae and Acinetobacter baumanii | ≤ 16 | 32 - 64 | ≥ 128 | ≥ 21 | 18 - 20 | ≤ 17 |
| Haemophilus influenzaea | ≤ 1 | - | ≥ 2 | - | - | - |
| Pseudomonas aeruginosa | ≤ 64 | - | ≥ 128 | ≥ 18 | - | ≤ 17 |
| Staphylococcus aureus | ≤ 8 | - | ≥ 16 | ≥ 20 | - | ≤ 19 |
| Bacteroides fragilis group | ≤ 32 | 64 | ≥ 128 | - | - | - |
A report of S (“Susceptible”) indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentration usually achievable. A report of I (“Intermediate”) indicates that the results should be considered equivocal, and if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone, which prevents small, uncontrolled technical factors from causing major discrepancies in interpretation. A report of R (“Resistant”) indicates that the pathogen is not likely to be inhibited if the antimicrobial compound in the blood reaches the concentration usually achievable; other therapy should be considered.
Quality Control
Standardized susceptibility test procedures require the use of quality control microorganisms to control the technical aspects of the test procedures.1,2,3,4 Standard piperacillin/tazobactam powder should provide the following ranges of values noted in Table 3. Quality control microorganisms are specific strains of microorganisms with intrinsic biological properties relating to resistance mechanisms and their genetic expression within the microorganism; the specific strains used for microbiological quality control are not clinically significant.
| Acceptable Quality Control Ranges | ||
|---|---|---|
| a This quality control range for Haemophilus influenzae is applicable only to tests performed using Haemophilus Test Medium inoculated with a direct colony suspension and incubated at 35°C in ambient air for 20 to 24 hours. | ||
| Minimum Inhibitory Concentration | Disk Diffusion | |
| QC Strain | Range (MIC in μg/mL) | Zone Diameter Ranges in mm |
| Escherichia coli ATCC 25922 | 1 - 4 | 24 - 30 |
| Escherichia coli ATCC 35218 | 0.5 - 2 | 24 - 30 |
| Pseudomonas aeruginosa ATCC 27853 | 1 - 8 | 25 - 33 |
| Haemophilus influenzaea ATCC 49247 | 0.06 - 0.5 | - |
| Staphylococcus aureus ATCC 29213 | 0.25 - 2 | - |
| Staphylococcus aureus ATCC 25923 | - | 27 - 36 |
| Bacteroides fragilis ATCC 25285 | 0.12 - 0.5 | - |
| Bacteroides thetaiotaomicron ATCC 29741 | 4 - 16 | - |
INDICATIONS AND USAGE
Zosyn (piperacillin and tazobactam for injection, USP) is indicated for the treatment of patients with moderate to severe infections caused by piperacillin-resistant, piperacillin/tazobactam-susceptible, β-lactamase producing strains of the designated microorganisms in the specified conditions listed below:
Appendicitis (complicated by rupture or abscess) and peritonitis caused by piperacillin-resistant, β-lactamase producing strains of Escherichia coli or the following members of the Bacteroides fragilis group: B. fragilis, B. ovatus, B. thetaiotaomicron, or B. vulgatus. The individual members of this group were studied in less than 10 cases.
Uncomplicated and complicated skin and skin structure infections, including cellulitis, cutaneous abscesses, and ischemic/diabetic foot infections caused by piperacillin-resistant, β-lactamase producing strains of Staphylococcus aureus.
Postpartum endometritis or pelvic inflammatory disease caused by piperacillin-resistant, β-lactamase producing strains of Escherichia coli.
Community-acquired pneumonia (moderate severity only) caused by piperacillin-resistant, β-lactamase producing strains of Haemophilus influenzae.
Nosocomial pneumonia (moderate to severe) caused by piperacillin-resistant, β-lactamase producing strains of Staphylococcus aureus and by piperacillin/tazobactam-susceptible Acinetobacter baumanii, Haemophilus influenzae, Klebsiella pneumoniae, and Pseudomonas aeruginosa (Nosocomial pneumonia caused by P. aeruginosa should be treated in combination with an aminoglycoside). (See DOSAGE AND ADMINISTRATION.)
Zosyn (piperacillin and tazobactam for injection, USP) is indicated only for the specified conditions listed above. Infections caused by piperacillin-susceptible organisms, for which piperacillin has been shown to be effective, are also amenable to Zosyn treatment due to its piperacillin content. The tazobactam component of this combination product does not decrease the activity of the piperacillin component against piperacillin-susceptible organisms. Therefore, the treatment of mixed infections caused by piperacillin-susceptible organisms and piperacillin-resistant, β-lactamase producing organisms susceptible to Zosyn should not require the addition of another antibiotic. (See DOSAGE AND ADMINISTRATION.)
Zosyn is useful as presumptive therapy in the indicated conditions prior to the identification of causative organisms because of its broad spectrum of bactericidal activity against gram-positive and gram-negative aerobic and anaerobic organisms.
Appropriate cultures should usually be performed before initiating antimicrobial treatment in order to isolate and identify the organisms causing infection and to determine their susceptibility to Zosyn. Antimicrobial therapy should be adjusted, if appropriate, once the results of culture(s) and antimicrobial susceptibility testing are known.
To reduce the development of drug-resistant bacteria and maintain the effectiveness of Zosyn (piperacillin and tazobactam) injection and other antibacterial drugs, Zosyn (piperacillin and tazobactam) should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.
CONTRAINDICATIONS
Zosyn is contraindicated in patients with a history of allergic reactions to any of the penicillins, cephalosporins, or β-lactamase inhibitors.
WARNINGS
SERIOUS AND OCCASIONALLY FATAL HYPERSENSITIVITY (ANAPHYLACTIC/ANAPHYLACTOID) REACTIONS (INCLUDING SHOCK) HAVE BEEN REPORTED IN PATIENTS RECEIVING THERAPY WITH PENICILLINS INCLUDING Zosyn. THESE REACTIONS ARE MORE LIKELY TO OCCUR IN INDIVIDUALS WITH A HISTORY OF PENICILLIN HYPERSENSITIVITY OR A HISTORY OF SENSITIVITY TO MULTIPLE ALLERGENS. THERE HAVE BEEN REPORTS OF INDIVIDUALS WITH A HISTORY OF PENICILLIN HYPERSENSITIVITY WHO HAVE EXPERIENCED SEVERE REACTIONS WHEN TREATED WITH CEPHALOSPORINS. BEFORE INITIATING THERAPY WITH Zosyn, CAREFUL INQUIRY SHOULD BE MADE CONCERNING PREVIOUS HYPERSENSITIVITY REACTIONS TO PENICILLINS, CEPHALOSPORINS, OR OTHER ALLERGENS. IF AN ALLERGIC REACTION OCCURS, Zosyn SHOULD BE DISCONTINUED AND APPROPRIATE THERAPY INSTITUTED. SERIOUS ANAPHYLACTIC/ANAPHYLACTOID REACTIONS (INCLUDING SHOCK) REQUIRE IMMEDIATE EMERGENCY TREATMENT WITH EPINEPHRINE. OXYGEN, INTRAVENOUS STEROIDS, AND AIRWAY MANAGEMENT, INCLUDING INTUBATION, SHOULD ALSO BE ADMINISTERED AS INDICATED.
Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including Zosyn, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.
C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.
If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.
PRECAUTIONS
General
Bleeding manifestations have occurred in some patients receiving β-lactam antibiotics, including piperacillin. These reactions have sometimes been associated with abnormalities of coagulation tests such as clotting time, platelet aggregation and prothrombin time, and are more likely to occur in patients with renal failure. If bleeding manifestations occur, Zosyn (piperacillin and tazobactam for injection, USP) should be discontinued and appropriate therapy instituted.
The possibility of the emergence of resistant organisms that might cause superinfections should be kept in mind. If this occurs, appropriate measures should be taken.
As with other penicillins, patients may experience neuromuscular excitability or convulsions if higher than recommended doses are given intravenously (particularly in the presence of renal failure).
Zosyn contains a total of 2.79 mEq (64 mg) of Na+ per gram of piperacillin in the combination product. This should be considered when treating patients requiring restricted salt intake. Periodic electrolyte determinations should be performed in patients with low potassium reserves, and the possibility of hypokalemia should be kept in mind with patients who have potentially low potassium reserves and who are receiving cytotoxic therapy or diuretics.
As with other semisynthetic penicillins, piperacillin therapy has been associated with an increased incidence of fever and rash in cystic fibrosis patients.
In patients with creatinine clearance ≤ 40 mL/min and dialysis patients (hemodialysis and CAPD), the intravenous dose should be adjusted to the degree of renal function impairment. (See DOSAGE AND ADMINISTRATION.)
Prescribing Zosyn (piperacillin and tazobactam) in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of development of drug-resistant bacteria.
Information for Patients
Patients should be counseled that antibacterial drugs, including Zosyn, should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When Zosyn is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by Zosyn or other antibacterial drugs in the future.
Diarrhea is a common problem caused by antibiotics which usually ends when the antibiotic is discontinued. Sometimes after starting treatment with antibiotics, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibiotic. If this occurs, patients should contact their physician as soon as possible.
Laboratory Tests
Periodic assessment of hematopoietic function should be performed, especially with prolonged therapy, i.e., ≥ 21 days. (See ADVERSE REACTIONS, Adverse Laboratory Events.)
Drug Interactions
Aminoglycosides
The mixing of beta-lactam antibiotics with aminoglycosides in vitro can result in substantial inactivation of the aminoglycoside. However, amikacin and gentamicin have been shown to be compatible in vitro with reformulated Zosyn containing EDTA supplied in vials or bulk pharmacy containers in certain diluents at specific concentrations for a simultaneous Y-site infusion. (See DOSAGE AND ADMINISTRATION.) Reformulated Zosyn containing EDTA is not compatible with tobramycin for simultaneous coadministration via Y-site infusion.
The inactivation of aminoglycosides in the presence of penicillin-class drugs has been recognized. It has been postulated that penicillin-aminoglycoside complexes form; these complexes are microbiologically inactive and of unknown toxicity. Sequential administration of Zosyn with tobramycin to patients with normal renal function and mild to moderate renal impairment has been shown to modestly decrease serum concentrations of tobramycin but does not significantly affect tobramycin pharmacokinetics. When aminoglycosides are administered in combination with piperacillin to patients with end-stage renal disease requiring hemodialysis, the concentrations of the aminoglycosides (especially tobramycin) may be significantly altered and should be monitored. Since aminoglycosides are not equally susceptible to inactivation by piperacillin, consideration should be given to the choice of the aminoglycoside when administered in combination with piperacillin to these patients.
Probenecid
Probenecid administered concomitantly with Zosyn prolongs the half-life of piperacillin by 21% and that of tazobactam by 71%.
Vancomycin
No pharmacokinetic interactions have been noted between Zosyn and vancomycin.
Heparin
Coagulation parameters should be tested more frequently and monitored regularly during simultaneous administration of high doses of heparin, oral anticoagulants, or other drugs that may affect the blood coagulation system or the thrombocyte function.
Vecuronium
Piperacillin when used concomitantly with vecuronium has been implicated in the prolongation of the neuromuscular blockade of vecuronium. Zosyn (piperacillin/tazobactam) could produce the same phenomenon if given along with vecuronium. Due to their similar mechanism of action, it is expected that the neuromuscular blockade produced by any of the non-depolarizing muscle relaxants could be prolonged in the presence of piperacillin. (See package insert for vecuronium bromide.)
Methotrexate
Limited data suggests that co-administration of methotrexate and piperacillin may reduce the clearance of methotrexate due to competition for renal secretion. The impact of tazobactam on the elimination of methotrexate has not been evaluated. If concurrent therapy is necessary, serum concentrations of methotrexate as well as the signs and symptoms of methotrexate toxicity should be frequently monitored.
Drug/Laboratory Test Interactions
As with other penicillins, the administration of Zosyn (piperacillin and tazobactam for injection, USP) may result in a false-positive reaction for glucose in the urine using a copper-reduction method (CLINITEST®). It is recommended that glucose tests based on enzymatic glucose oxidase reactions (such as DIASTIX® or TES-TAPE) be used.
There have been reports of positive test results using the Bio-Rad Laboratories Platelia Aspergillus EIA test in patients receiving piperacillin/tazobactam injection who were subsequently found to be free of Aspergillus infection. Cross-reactions with non-Aspergillus polysaccharides and polyfuranoses with the Bio-Rad Laboratories Platelia Aspergillus EIA test have been reported.
Therefore, positive test results in patients receiving piperacillin/tazobactam should be interpreted cautiously and confirmed by other diagnostic methods.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Long-term carcinogenicity studies in animals have not been conducted with piperacillin/tazobactam, piperacillin, or tazobactam.
Piperacillin/Tazobactam
Piperacillin/tazobactam was negative in microbial mutagenicity assays at concentrations up to 14.84/1.86 μg/plate. Piperacillin/tazobactam was negative in the unscheduled DNA synthesis (UDS) test at concentrations up to 5689/711 μg/mL. Piperacillin/tazobactam was negative in a mammalian point mutation (Chinese hamster ovary cell HPRT) assay at concentrations up to 8000/1000 μg/mL. Piperacillin/tazobactam was negative in a mammalian cell (BALB/c-3T3) transformation assay at concentrations up to 8/1 μg/mL. In vivo, piperacillin/tazobactam did not induce chromosomal aberrations in rats dosed I.V. with 1500/187.5 mg/kg; this dose is similar to the maximum recommended human daily dose on a body-surface-area basis (mg/m2).
Piperacillin
Piperacillin was negative in microbial mutagenicity assays at concentrations up to 50 μg/plate. There was no DNA damage in bacteria (Rec assay) exposed to piperacillin at concentrations up to 200 μg/disk. Piperacillin was negative in the UDS test at concentrations up to 10,000 μg/mL. In a mammalian point mutation (mouse lymphoma cells) assay, piperacillin was positive at concentrations ≥2500 μg/mL. Piperacillin was negative in a cell (BALB/c-3T3) transformation assay at concentrations up to 3000 μg/mL. In vivo, piperacillin did not induce chromosomal aberrations in mice at I.V. doses up to 2000 mg/kg/day or rats at I.V. doses up to 1500 mg/kg/day. These doses are half (mice) or similar (rats) to the maximum recommended human daily dose based on body-surface area (mg/m2). In another in vivo test, there was no dominant lethal effect when piperacillin was administered to rats at I.V. doses up to 2000 mg/kg/day, which is similar to the maximum recommended human daily dose based on body-surface area (mg/m2). When mice were administered piperacillin at I.V. doses up to 2000 mg/kg/day, which is half the maximum recommended human daily dose based on body-surface area (mg/m2), urine from these animals was not mutagenic when tested in a microbial mutagenicity assay. Bacteria injected into the peritoneal cavity of mice administered piperacillin at I.V. doses up to 2000 mg/kg/day did not show increased mutation frequencies.
Tazobactam
Tazobactam was negative in microbial mutagenicity assays at concentrations up to 333 μg/plate. Tazobactam was negative in the UDS test at concentrations up to 2000 μg/mL. Tazobactam was negative in a mammalian point mutation (Chinese hamster ovary cell HPRT) assay at concentrations up to 5000 μg/mL. In another mammalian point mutation (mouse lymphoma cells) assay, tazobactam was positive at concentrations ≥3000 μg/mL. Tazobactam was negative in a cell (BALB/c-3T3) transformation assay at concentrations up to 900 μg/mL. In an in vitro cytogenetics (Chinese hamster lung cells) assay, tazobactam was negative at concentrations up to 3000 μg/mL. In vivo, tazobactam did not induce chromosomal aberrations in rats at I.V. doses up to 5000 mg/kg, which is 23 times the maximum recommended human daily dose based on body-surface area (mg/m2).
Pregnancy
Teratogenic effects—Pregnancy Category B
Piperacillin/tazobactam
Reproduction studies have been performed in rats and have revealed no evidence of impaired fertility due to piperacillin/tazobactam administered up to a dose which is similar to the maximum recommended human daily dose based on bo
