What are the differences in using Zosyn (piperacillin/tazobactam) versus Unasyn (ampicillin/sulbactam) for treating infections?

From the Guidelines

Zosyn (piperacillin/tazobactam) is generally preferred over Unasyn (ampicillin/sulbactam) for treating infections, especially in cases of healthcare-associated infections, severe intra-abdominal infections, and when Pseudomonas aeruginosa is suspected, due to its broader coverage against gram-negative organisms and enhanced activity against many anaerobes and some gram-positive bacteria 1.

Key Differences

• Zosyn has a broader spectrum of activity, including coverage against Pseudomonas aeruginosa, making it more suitable for healthcare-associated infections and severe intra-abdominal infections.
• Unasyn lacks Pseudomonas coverage but remains effective against many community-acquired infections, making it more appropriate for cellulitis, community-acquired pneumonia, and uncomplicated intra-abdominal infections.
• The difference in spectrum relates to piperacillin's enhanced activity against gram-negative bacteria compared to ampicillin.

Dosage and Administration

• Typical Zosyn dosing is 3.375g or 4.5g IV every 6-8 hours, with adjustments needed for renal impairment.
• Standard Unasyn dosing is 1.5-3g IV every 6 hours.

Side Effects and Monitoring

• Both medications require monitoring for allergic reactions, particularly in patients with penicillin allergies.
• Similar side effects include diarrhea, rash, and electrolyte abnormalities.

Clinical Applications

• Zosyn is preferred for healthcare-associated infections, severe intra-abdominal infections, and cases where Pseudomonas is suspected.
• Unasyn is more appropriate for community-acquired infections like cellulitis, community-acquired pneumonia, and uncomplicated intra-abdominal infections, as supported by guidelines for the management of intra-abdominal infections 1 and skin and soft tissue infections 1.

From the FDA Drug Label

INDICATIONS AND USAGE Piperacillin and tazobactam for injection is a combination of piperacillin, a penicillin-class antibacterial and tazobactam, a beta-lactamase inhibitor, indicated for the treatment of: Intra-abdominal infections in adult and pediatric patients 2 months of age and older (1.1) Nosocomial pneumonia in adult and pediatric patients 2 months of age and older (1. 2) Skin and skin structure infections in adults (1.3) Female pelvic infections in adults (1.4) Community-acquired pneumonia in adults (1. 5) INDICATIONS AND USAGE Ampicillin and Sulbactam for Injection, USP, is indicated for the treatment of infections due to susceptible strains of the designated microorganisms in the conditions listed below. Skin and Skin Structure Infectionscaused by beta-lactamase producing strains of Staphylococcus aureus, Escherichia coli, *Klebsiella spp. (including K. pneumoniae), Proteus mirabilis,*Bacteroides fragilis, *Enterobacter spp., *and Acinetobacter calcoaceticus.

The main differences between Zosyn (piperacillin/tazobactam) and Unasyn (ampicillin/sulbactam) are:

• Indications: Zosyn is indicated for a broader range of infections, including nosocomial pneumonia and community-acquired pneumonia, whereas Unasyn is primarily indicated for skin and skin structure infections, intra-abdominal infections, and gynecological infections.
• Spectrum of activity: Zosyn has a broader spectrum of activity against Gram-negative bacteria, including Pseudomonas aeruginosa, whereas Unasyn is more effective against Gram-positive bacteria, including Staphylococcus aureus.
• Pediatric use: Zosyn is approved for use in pediatric patients 2 months of age and older, whereas Unasyn has limited data on use in pediatric patients and should be used with caution in this population 2 3.
• Dosage and administration: The dosage and administration of Zosyn and Unasyn may differ, and should be guided by the specific product labeling and clinical judgment. Key points to consider when choosing between Zosyn and Unasyn include:
• The severity and type of infection being treated
• The susceptibility of the causative organism to the antibiotic
• The patient's age, weight, and renal function
• The potential for adverse reactions and interactions with other medications.

From the Research

Comparison of Zosyn and Unasyn

• Zosyn (piperacillin/tazobactam) and Unasyn (ampicillin/sulbactam) are both beta-lactam/beta-lactamase inhibitor combinations used to treat bacterial infections 4.
• Zosyn has a broader spectrum of antibacterial activity, encompassing most Gram-positive and Gram-negative aerobic bacteria and anaerobic bacteria, including many pathogens producing beta-lactamases 4.
• Unasyn is effective against a variety of bacterial infections, including those caused by beta-lactamase-producing strains, but its spectrum of activity is not as broad as Zosyn 5.

Efficacy in Treating Infections

• Zosyn has been shown to be effective in treating lower respiratory tract, intra-abdominal, urinary tract, gynaecological, and skin/soft tissue infections, as well as fever in patients with neutropenia 4.
• Unasyn is effective against infections such as bacteremia, pneumonia, meningitis, urinary tract infection, and skin and soft-tissue infections, particularly those caused by Acinetobacter baumannii 5.
• Zosyn has been compared to other antibiotics, such as carbapenems, and has been found to be effective in treating Pseudomonas aeruginosa bloodstream infections 6, 7.

Adverse Events and Resistance

• Zosyn is generally well tolerated, with the most frequent adverse events being gastrointestinal symptoms and skin reactions 4.
• Unasyn can cause adverse events such as gastrointestinal symptoms, skin reactions, and allergic reactions 5.
• The use of Zosyn and Unasyn can contribute to the development of antibiotic resistance, particularly in the case of carbapenem-resistant Acinetobacter strains 8, 5.

Clinical Use

• Zosyn is often used as empirical therapy for patients with severe infections, including sepsis, and is a carbapenem-sparing agent to reduce the incidence of multidrug-resistant bacteria and superinfections 8.
• Unasyn is used to treat a variety of bacterial infections, particularly those caused by beta-lactamase-producing strains, and is often used in combination with other antibiotics 5.
• The choice between Zosyn and Unasyn depends on the specific infection being treated, the susceptibility patterns of the causative organism, and the patient's individual needs and medical history 4, 5.