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## Piperacillin/Tazobactam (Zosyn) ### Overview Piperacillin/tazobactam is a combination of an extended-spectrum penicillin antibiotic and a beta-lactamase inhibitor. It is active against many Gram-positive, Gram-negative, and anaerobic bacteria. ### Primary Indications * Complicated intra-abdominal infections * Complicated skin and skin structure infections * Community-acquired pneumonia * Hospital-acquired pneumonia (including ventilator-associated pneumonia) * Febrile neutropenia (empiric treatment) ### Adult Dosing * **Standard Dose:** 3.375 grams (piperacillin 3g/tazobactam 0.375g) every 6 hours or 4.5 grams (piperacillin 4g/tazobactam 0.5g) every 6 or 8 hours intravenously. * **Higher Doses (e.g., severe infections, suspected resistant organisms):** May be used up to 4.5 grams every 4 hours or 12 grams (piperacillin 9g/tazobactam 1.125g) every 8 hours (continuous infusion). Specific dosing depends on institutional protocols and clinical judgment. * **Duration:** Typically 7-14 days, depending on the infection site, severity, and clinical response. ### Pediatric Dosing * **Children 2 months to 12 years:** * **Dose:** 90 to 112.5 mg piperacillin equivalents per kg per dose, administered every 6 or 8 hours intravenously. * **Maximum dose:** 4.5 grams per dose for every 6-hour dosing, or 3.375 grams per dose for every 8-hour dosing. * **Note:** Dosing is based on piperacillin content. Continuous infusion may be used for critically ill patients. * **Neonates and Infants < 2 months:** Dosing is not well established due to immature renal and hepatic function. Use with caution and consider dose adjustments. ### Dose Adjustments * **Renal Impairment (CrCl ≤ 40 mL/min):** Reduce dose and/or increase interval. * **3.375g every 6h:** Reduce to 2.25g every 6h or 2g every 8h. * **4.5g every 6h:** Reduce to 3.375g every 6h or 2.25g every 8h. * **4.5g every 8h:** Reduce to 3.375g every 8h or 2.25g every 12h. * **Hepatic Impairment:** No specific dose adjustment recommended, but use with caution. ### Contraindications * Known serious allergy to penicillin class antibiotics, piperacillin, tazobactam, or any component of the formulation. ### Adverse Effects * **Common:** Diarrhea, nausea, vomiting, rash, headache, insomnia, eosinophilia, elevated liver enzymes, hypokalemia. * **Serious:** *Clostridioides difficile*-associated diarrhea (CDAD), hypersensitivity reactions (including anaphylaxis), seizures (especially with renal impairment or high doses), interstitial nephritis, hematologic changes (neutropenia, thrombocytopenia). ### Key Drug Interactions * **Probenecid:** May increase piperacillin/tazobactam levels. * **Aminoglycosides:** In vitro antagonism with certain Gram-negative bacteria; consider separate administration if co-administered. * **Neuromuscular Blockers (e.g., vecuronium):** Piperacillin may prolong the neuromuscular blockade. * **Warfarin:** May decrease the effect of warfarin. Monitor INR closely. * **Methotrexate:** May decrease methotrexate clearance; monitor methotrexate levels. ### Monitoring * Renal function (baseline and periodically). * Liver function tests. * Electrolytes (especially potassium). * Complete blood count (especially with prolonged therapy). * Signs and symptoms of infection, including fever, inflammation, and culture results. * Signs of hypersensitivity reactions. * Stool for *C. difficile* if diarrhea develops. ### Clinical Pearls * The ratio of piperacillin to tazobactam is typically 8:1. * Piperacillin/tazobactam is a broad-spectrum agent and should be used judiciously to minimize resistance. * Reconstitution and dilution for IV administration are crucial. Ensure adequate dilution to prevent infusion phlebitis. * Continuous infusion may be preferred for severe infections or critically ill patients to maintain higher drug concentrations and potentially improve outcomes. * Discontinue if allergic reaction occurs. *** *Disclaimer: This information is for educational purposes and should not replace current prescribing information or clinical judgment. Always consult the official drug labeling and institutional guidelines for complete and up-to-date information before making any clinical decisions.*