Zosyn dosage, forms, and strengths

Zosyn is the brand name for piperacillin/tazobactam, an injectable combination antibiotic made by the pharmaceutical company Pfizer. It includes the antibacterial piperacillin sodium and the beta-lactamase inhibitor tazobactam sodium. The mechanism of action in this antimicrobial drug involves stopping cell wall synthesis in certain bacteria. It is classified as bactericidal.

Piperacillin/tazobactam is frequently combined with other antibiotics for greater coverage for serious infections. This medication is effective against several different bacteria and can be used to manage infections in various locations in the body. Intravenous therapy is the only available type of administration for this medication, so its use is primarily in the hospital setting.

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Zosyn forms and strengths

The only dosage forms for Zosyn are solutions used for intravenous treatment. Here are the available formulations:

• 2.25 g per 50 mL (2 gm piperacillin + 0.25 gm tazobactam) 

• 3.375 g per 50mL (3 gm piperacillin + 0.375 gm tazobactam)

• 4.5 g per 100 mL (4 gm piperacillin + 0.5 gm tazobactam)

Zosyn dosage for adults

Zosyn is a broad-spectrum antibiotic agent. It is shown to be effective against various bacteria both in vitro and within the body. Here are some of the pathogens susceptible to this antibacterial medication:

• Gram-positive bacteria:

  • Staphylococcus aureus (methicillin-susceptible)

• Gram-negative bacteria:

  • Acinetobacter baumannii

  • Escherichia coli

  • Haemophilus influenzae 

  • Klebsiella pneumoniae

  • Pseudomonas aeruginosa 

• Anaerobic bacteria:

  • Bacteroides fragilis group 

Here are the common medical conditions that are successfully treated with the use of Zosyn:

• Appendicitis

• Cellulitis

• Cutaneous abscesses

• Diabetic foot infections

• Pelvic inflammatory disease

• Peritonitis

• Pneumonia

• Postpartum endometritis

* There are several off-label treatments for other health conditions that are not listed.

Zosyn dosage for gynecological infections

Zosyn is approved for the treatment of postpartum endometritis or pelvic inflammatory disease caused by beta-lactamase isolates of Escherichia coli.

• Administer 3.375 g IV every six hours for seven to 10 days

Zosyn dosage for intra-abdominal infections

Zosyn is approved for the treatment of ruptured/complicated appendicitis and peritonitis caused by beta-lactamase isolates of Escherichia coli or Bacteroides fragilis, ovatus, thetaiotaomicron, or vulgatus.

• Administer 3.375 g IV every six hours for four to seven days

Zosyn dosage for pneumonia

Zosyn is approved for the treatment of community-acquired and nosocomial pneumonia caused by beta-lactamase isolates of Staphylococcus aureus, Acinetobacter baumannii, Haemophilus influenzae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. 

• Administer 4.5 g IV every six hours for seven days 

• Nosocomial pneumonia caused by P. aeruginosa should be treated with Zosyn and an aminoglycoside antibacterial agent

RELATED: Is pneumonia contagious?

Zosyn dosage for skin/skin structure infections

Zosyn is approved for the treatment of uncomplicated and complicated skin and skin structure infections caused by beta-lactamase isolates of Staphylococcus aureus.

• Administer 3.375 g IV every six hours for seven to 10 days

Zosyn dosage for children

Zosyn may be used in children as young as 2 months old, but pediatric dosing depends on the condition being treated and the patient’s weight.

Zosyn dosage for pediatric intra-abdominal infections

Zosyn is approved for the treatment of ruptured/complicated appendicitis and peritonitis caused by beta-lactamase isolates of Escherichia coli or Bacteroides fragilis, ovatus, thetaiotaomicron, or vulgatus in pediatric patients at least 2 months old.

• 2-9 months: 

  • Administer 90 mg/kg (80 mg piperacillin and 10 mg tazobactam) IV every eight hours for four to seven days

• Older than 9 months:

  • Less than 40 kg: Administer 112.5 mg/kg (100 mg piperacillin and 12.5 mg tazobactam) IV every eight hours for four to seven days

  • More than 40 kg: Administer 3.375 g IV every six hours for four to seven days (adult dosage)

Zosyn dosage for pediatric pneumonia

Zosyn is approved for the treatment of nosocomial pneumonia caused by beta-lactamase isolates of Staphylococcus aureus, Acinetobacter baumannii, Haemophilus influenzae, Klebsiella pneumoniae, and Pseudomonas aeruginosa in pediatric patients at least 2 months old. 

• 2-9 months: 

  • Administer 90 mg/kg (80 mg piperacillin and 10 mg tazobactam) IV every six hours for seven to 14 days

• Older than 9 months:

  • Less than 40 kg: Administer 112.5 mg/kg (100 mg piperacillin and 12.5 mg tazobactam) IV every six hours for seven to 14 days

  • More than 40 kg: Administer 4.5 g IV every six hours for seven to 14 days 

• Hospital-acquired pneumonia caused by P. aeruginosa should be treated with Zosyn and an aminoglycoside antibacterial agent just as with adult patients

Zosyn dosage restrictions

• Contraindications of Zosyn include any individual that has a known allergic reaction to penicillin, cephalosporins, or beta-lactam antibiotics. 

• Other conditions such as a history of low potassium levels, cystic fibrosis, diarrhea from C. difficile, seizure disorders, and renal failure should be discussed with your healthcare provider as different dosages may be required. Occasionally, avoidance of this medication altogether may be required if the risks outweigh the benefits of taking this antibiotic.

• No dosing modifications are required for those with hepatic impairment. 

• Zosyn is also safe for senior populations. 

Renal impairment

A patient’s renal function must be monitored closely while taking Zosyn. If there is a history of impaired renal function, special dosing will be required. Renal impairment dosing recommendations for Zosyn are as follows.

Dosing alternative for 3.375 g IV every 6 hours for renal impairment:

• Creatinine clearance (CrCl) 20-40: 2.25 g IV every six hours

• CrCl less than 20: 2.25 g IV every eight hours

• Hemodialysis patients: 2.25 g IV every 12 hours

  • Give 0.75 g supplement after dialysis if next dose is not close after completing dialysis treatment

• Peritoneal dialysis patients: 2.25 g IV every 12 hours

  • No supplements required

Dosing alternative for 4.5 g IV every 6 hours for renal impairment:

• Creatinine clearance (CrCl) 20-40: 3.375 g IV every six hours

• CrCl less than 20: 2.25 g IV every six hours

• Hemodialysis patients: 2.25 g IV every eight hours

  • Give 0.75 g supplement after dialysis if next dose is not close after completing dialysis treatment

• Peritoneal dialysis patients: 2.25 g IV every eight hours

  • No supplements required

Zosyn dosage for pets 

Zosyn is also available for prescribing in pets when indicated by a veterinarian. This medication is only approved by the United States Food and Drug Administration (FDA) for humans, but veterinarians have the approval to use the medication in some instances for certain pathogens and bacterial infections. Zosyn can only be administered to animals as an injection just like in humans. 

How to take Zosyn

Zosyn is only available in an injectable form, which means typically your healthcare provider must provide this to you.

• Your doctor will prescribe your dose and schedule. This medicine is given through a needle placed in a vein. The medicine must be injected slowly, so your IV tube will need to stay in place for at least 30 minutes.

• A nurse or other health provider will give you this medicine.

Pharmacy bulk vials

These forms of reconstituted stock solutions must be diluted prior to use. Pharmacy bulk vials are used in the hospital setting. Sterile dispensing systems must be utilized for reconstitution, and the entire supply must be used within 24 hours if stored at room temperature and within 48 hours if refrigerated.

Single-dose vials

These vials of reconstituted Zosyn must use a diluent of 10 mL, 15 mL, or 20 mL. 

Examples of diluents that can be used with pharmacy bulk vials and single-dose vials include 0.9% sodium chloride for injection, sterile water for injection, dextrose 5%, bacteriostatic saline/parabens, bacteriostatic water/parabens, bacteriostatic saline/benzyl alcohol, and bacteriostatic water/benzyl alcohol dilution.

Intravenous solutions must be further diluted for reconstituted Zosyn. These further dilution options include 0.9% sodium chloride, sterile water for injection or infusion, dextran 6% in saline, dextrose 5%, lactated ringer's solution (only with Zosyn containing EDTA).

Zosyn dosage FAQs

How long does Zosyn stay in your system?

The pharmacokinetics for Zosyn show that the plasma half-life of piperacillin and of tazobactam is 0.7 to 1.2 hours regardless of the dose used or duration of infusion. Both are eliminated from the body through the kidney.

What happens if I miss a dose of Zosyn?

If a dose is missed of Zosyn, your next dose should be given as soon as possible. Two doses should never be given at the same time. 

How long can you take Zosyn?

Zosyn is usually prescribed for seven to 10 days. Nosocomial pneumonia Zosyn use is for seven to 14 days. The prescription should be taken for the entire recommended length of time even if symptoms improve to prevent developing resistance to the antibiotic. 

What is the maximum dosage for Zosyn?

For all conditions other than nosocomial pneumonia, the maximum dosage for Zosyn includes 3.375 g every six hours totaling a daily dose of 13.5 g (12.0 g piperacillin/1.5 g tazobactam). The maximum dosage for nosocomial pneumonia is 4.5 g every six hours totaling a daily dose of 18.0 g (16.0 g piperacillin/2.0 g tazobactam).

Can you overdose on Zosyn?

There have been some reports of patients overdosing with Zosyn. Typically minor symptoms have occurred with overdose, but more serious adverse effects have also occurred such as convulsions. The concentrations of Zosyn within the system can be reduced with hemodialysis. Symptoms to be aware of while taking Zosyn include:

Serious side effects

• Hypersensitivity reaction or anaphylaxis

• Serum sickness

• Eosinophilia

• Stevens-Johnson syndrome

• Toxic epidermal necrolysis

• Interstitial nephritis

• Superinfection

• C. difficile diarrhea

• Anemia or bleeding

• Hypokalemia

• Seizures

Common side effects

• Diarrhea or constipation

• Headache

• Nausea or vomiting

• Insomnia

• Rash or pruritus

• Fever

• Agitation

• Electrolyte abnormalities

• Elevated liver enzymes

What interacts with Zosyn?

There are a number of drug interactions that may occur with the use of Zosyn. All medications should be disclosed to your healthcare provider for the prevention of adverse reactions. Some important medications that may cause serious adverse reactions include:

• Aminoglycosides (especially tobramycin)

• Probenecid

• Vancomycin

• Anticoagulants (high doses of heparin, coumadin, etc.)

• Vecuronium

• Methotrexate

Is it safe to take Zosyn during pregnancy?

Zosyn is confirmed to cross the placenta but there is no known data showing harm to the fetus or being linked to miscarriage. Zosyn is also approved for use while breastfeeding. Piperacillin is excreted into breast milk but there are no studies confirming harm to the child.

Related resources for Zosyn dosages:

• Piperacillin with tazobactam, Plumb’s veterinary

• Zosyn, Epocrates

• Zosyn dosage and administration, Pfizer

• Pregnancy/lactation, Epocrates