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## Piperacillin/Tazobactam (Zosyn)
### Overview
Piperacillin/tazobactam is a combination penicillin-class antibiotic and beta-lactamase inhibitor. It is bactericidal and has a broad spectrum of activity against many Gram-positive, Gram-negative, and anaerobic bacteria.
### Primary Indications
* Complicated intra-abdominal infections
* Complicated skin and skin-structure infections
* Community-acquired pneumonia
* Nosocomial pneumonia
* Febrile neutropenia (empiric treatment)
### Adult Dosing
* **Standard Dose:** 3.375 grams (3g piperacillin/0.375g tazobactam) IV every 6 hours.
* **High Dose:** 4.5 grams (4g piperacillin/0.5g tazobactam) IV every 6 hours.
* **Extended-Infusion Dosing:** 3.375 grams or 4.5 grams IV infused over 4 hours every 6 or 8 hours. This may increase efficacy against certain pathogens. Specific extended infusion protocols may vary.
* Maximum dose: 18 grams per day (divided into doses every 6 or 8 hours).
### Pediatric Dosing
Dosing is based on the piperacillin component:
* **3 months to 12 years:** 100 mg/kg piperacillin IV every 8 hours. Maximum 4 grams piperacillin per dose.
* **12 years and older:** Adult dosing is typically used.
* **Neonates and infants < 3 months:** Dosing is less established and highly dependent on institutional guidelines, often utilizing specific dosing regimens based on gestational and postnatal age.
### Dose Adjustments
* **Renal Impairment (CrCl < 40 mL/min):** Reduce dose frequency.
* Standard dose (3.375g q6h): Administer 2.25 grams (2g piperacillin/0.25g tazobactam) IV every 8 hours.
* High dose (4.5g q6h): Administer 3.375 grams IV every 8 hours.
* If on hemodialysis, administer dose after dialysis and supplement with an additional dose (e.g., 0.75g piperacillin/0.094g tazobactam) if dose missed.
* **Hepatic Impairment:** No specific dose adjustment is recommended, but caution is advised.
### Contraindications
* Hypersensitivity to piperacillin, tazobactam, other penicillins, or cephalosporins.
* History of cholestatic jaundice or hepatic dysfunction associated with piperacillin/tazobactam use.
### Adverse Effects
* **Common:** Diarrhea, rash, nausea, vomiting, headache, insomnia, abdominal pain, constipation, elevated liver enzymes (AST, ALT).
* **Serious:** *Clostridioides difficile*-associated diarrhea, hypersensitivity reactions (including anaphylaxis), seizures (rare, more common with high doses or renal impairment), interstitial nephritis, hematologic effects (neutropenia, thrombocytopenia, eosinophilia).
### Key Drug Interactions
* **Aminoglycosides:** May have synergistic activity, but also potential for antagonism at high concentrations. Coadministration should be carefully considered.
* **Probenecid:** May increase and prolong piperacillin/tazobactam serum concentrations.
* **Warfarin:** May decrease the anticoagulant effect of warfarin; increased INR monitoring is recommended.
* **Neuromuscular blocking agents:** May prolong the duration of neuromuscular blockade.
* **Live attenuated vaccines:** May decrease the efficacy of these vaccines.
### Monitoring
* Renal function (especially with concurrent nephrotoxic agents or in patients with pre-existing renal impairment).
* Liver function tests.
* Signs and symptoms of hypersensitivity reactions.
* Signs and symptoms of *Clostridioides difficile* infection.
* Hematologic parameters (CBC) with prolonged therapy.
### Clinical Pearls
* Piperacillin/tazobactam is often reconstituted with sterile water and then further diluted in a compatible IV fluid (e.g., 0.9% sodium chloride or 5% dextrose) for infusion. Reconstituted solutions are generally stable for 24 hours at room temperature or 48 hours refrigerated. Always check manufacturer's specific instructions.
* Extended infusion may improve outcomes, especially in critically ill patients or those with severe infections.
* Tazobactam protects piperacillin from degradation by many beta-lactamases, broadening its spectrum to include beta-lactamase producing organisms.
* Dosing adjustments in renal impairment are crucial to avoid accumulation and potential toxicity.
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**Disclaimer:** This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information and institutional guidelines before administering any medication.
