Zosyn

Zosyn is the brand name for the antibiotic combination piperacillin/tazobactam. Piperacillin is an extended‑spectrum penicillin that inhibits bacterial cell wall synthesis by binding penicillin‑binding proteins. Tazobactam is a beta‑lactamase inhibitor that protects piperacillin from degradation by certain beta‑lactamases, extending its activity against beta‑lactamase–producing organisms. The combination is administered by intravenous infusion.

Zosyn has broad‑spectrum activity against many Gram‑positive cocci (excluding methicillin‑resistant Staphylococcus aureus), a wide range of Gram‑negative rods including Pseudomonas aeruginosa, and anaerobes. It is not reliably active against organisms that produce certain beta‑lactamases or against MRSA; local susceptibility patterns should guide use. Resistance can develop, and combination therapy may be used in severe infections when broad coverage is needed.

Common indications include complicated intra‑abdominal infections, complicated skin and soft tissue infections, gynecologic infections, community‑ and hospital‑acquired pneumonia (including settings with Pseudomonas coverage), and neutropenic fever or sepsis in hospitalized patients. Treatment duration and dosing depend on the infection type, severity, and patient renal function.

Typical adult dosing involves 3.375 g every 6 hours or 4.5 g every 6–8 hours by IV infusion, with adjustments for renal impairment. Infusion is usually over about 30 minutes; longer or extended infusions may be used for serious infections. Duration is guided by clinical response and infection type.

Adverse effects are generally mild but can include diarrhea, nausea, rash, and hypersensitivity reactions. There is a risk of Clostridioides difficile infection and other superinfections. Caution in patients with penicillin allergy; monitor for cross‑reactivity. Pregnant patients should weigh benefits and risks, as piperacillin/tazobactam is generally considered acceptable when indicated. Drug interactions may occur with anticoagulants and nephrotoxic agents; renal function should be monitored.