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# Piperacillin/Tazobactam (Zosyn)
## Overview
Piperacillin/tazobactam is an extended-spectrum penicillin combined with a beta-lactamase inhibitor. It is active against many Gram-positive, Gram-negative (including *Pseudomonas aeruginosa*), and anaerobic bacteria.
## Primary Indications
* Complicated intra-abdominal infections (cIAI)
* Complicated skin and skin structure infections (cSSSI)
* Community-acquired pneumonia (CAP)
* Nosocomial pneumonia (HAP/VAP)
* Febrile neutropenia (empiric treatment)
* Empiric treatment of serious bacterial infections where *Pseudomonas aeruginosa* is suspected.
## Adult Dosing
Standard dosing is typically **3.375 g (3 g piperacillin / 0.375 g tazobactam) or 4.5 g (4 g piperacillin / 0.5 g tazobactam) intravenously every 6 or 8 hours.**
* **3.375 g IV every 6 hours:** Often used for less severe infections or when a lower dose is deemed appropriate.
* **4.5 g IV every 6 hours:** Commonly used for moderate to severe infections, including HAP/VAP, cIAI, cSSSI, and febrile neutropenia.
* **4.5 g IV every 8 hours:** May be used for less severe infections or in specific patient populations, but less common than q6h dosing.
Dosing frequency and duration depend on the severity of infection, pathogen susceptibility, and clinical response. For febrile neutropenia, duration is typically 7 days, but may be extended.
## Pediatric Dosing
Dosing is based on piperacillin component.
* **Neonates and Infants (< 12 months):** Dosing is highly variable and depends on gestational age, postnatal age, and indication. Consult specialized pediatric infectious disease resources or institutional guidelines.
* **Children (≥ 12 months):**
* **Complicated intra-abdominal infections:** 90-100 mg piperacillin/kg/dose intravenously every 6 hours. Maximum dose is typically 4.5 g every 6 hours.
* **Nosocomial pneumonia:** 90-100 mg piperacillin/kg/dose intravenously every 6 hours. Maximum dose is typically 4.5 g every 6 hours.
* **Febrile neutropenia:** 90-100 mg piperacillin/kg/dose intravenously every 6 hours. Maximum dose is typically 4.5 g every 6 hours.
Ensure the tazobactam dose is proportionate (1:8 piperacillin:tazobactam ratio).
## Dose Adjustments
* **Renal Impairment (CrCl < 40 mL/min):** Reduce the dose or increase the interval.
* **CrCl 20-40 mL/min:** Administer the usual dose every 8 hours.
* **CrCl < 20 mL/min:** Administer the usual dose every 12 hours.
* Doses for renal impairment are often based on the piperacillin component. Dosing adjustments for pediatric patients with renal impairment should be made cautiously and may require consultation with a pharmacist or pediatric nephrologist.
* **Hepatic Impairment:** No dose adjustment is generally required.
## Contraindications
* Known severe hypersensitivity to piperacillin, tazobactam, other penicillinase-resistant penicillins, or any component of the product.
* History of immediate or severe allergic reaction to a beta-lactam antibiotic.
## Adverse Effects
* **Common:** Diarrhea, rash, nausea, vomiting, headache, insomnia, fever, eosinophilia, elevated liver enzymes (AST, ALT).
* **Serious:** *Clostridioides difficile*-associated diarrhea (CDAD), hypersensitivity reactions (anaphylaxis), seizures (especially with high doses or renal impairment), neutropenia, thrombocytopenia, interstitial nephritis, hemolytic anemia.
## Key Drug Interactions
* **Probenecid:** May increase and prolong piperacillin/tazobactam serum concentrations.
* **Neuromuscular blocking agents (e.g., vecuronium):** Penicillins may prolong the blockade.
* **Warfarin:** Piperacillin may decrease the effect of warfarin; monitor INR closely.
* **Methotrexate:** Piperacillin may decrease methotrexate clearance; monitor methotrexate levels.
## Monitoring
* **Renal function:** Especially in patients with impaired renal function or receiving concomitant nephrotoxic agents.
* **Liver function tests:** Monitor for elevated transaminases.
* **Hematologic parameters:** CBC with differential and platelet count, particularly with prolonged therapy or high doses, to monitor for neutropenia, thrombocytopenia, or hemolytic anemia.
* **Electrolytes:** Especially if diarrhea is prominent or with renal impairment.
* **Signs and symptoms of infection:** Clinical response, fever, and WBC count.
* **Signs and symptoms of CDAD:** Diarrhea, abdominal cramping, fever.
## Clinical Pearls
* Piperacillin/tazobactam is typically administered as a continuous infusion or intermittent infusions over 30 minutes. Consult institutional guidelines for preferred administration method. Continuous infusion may lead to higher drug exposure and potentially improved outcomes in severe infections, particularly *Pseudomonas aeruginosa* infections.
* Reconstituted solutions are stable for 24 hours at room temperature or 48 hours when refrigerated. Infusion solutions are typically stable for 24 hours at room temperature or 7 days when refrigerated.
* The beta-lactamase inhibitor tazobactam broadens the spectrum of piperacillin to include many beta-lactamase-producing organisms, but not all (e.g., some carbapenemases).
* Empiric use in febrile neutropenia is common due to its broad spectrum, including *Pseudomonas aeruginosa*.
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*Disclaimer: This information is intended for clinical decision support and does not replace comprehensive drug information resources or institutional protocols. Always verify current prescribing information and consult with a pharmacist or physician for patient-specific recommendations.*
