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# Piperacillin/Tazobactam
## Overview
Piperacillin/tazobactam is a combination antibiotic consisting of an extended-spectrum penicillin (piperacillin) and a beta-lactamase inhibitor (tazobactam). It is active against many Gram-positive, Gram-negative, and anaerobic bacteria, including *Pseudomonas aeruginosa*.
## Primary Indications
* Complicated intra-abdominal infections
* Complicated skin and skin structure infections (including diabetic foot infections)
* Community-acquired pneumonia
* Nosocomial pneumonia
* Bacterial meningitis (in specific situations, often reserved for susceptible organisms or empirical therapy when resistance is high)
* Febrile neutropenia (empiric therapy)
* Other serious infections caused by piperacillin-susceptible organisms, including those due to *Pseudomonas aeruginosa*.
## Adult Dosing
Standard adult dose: 3.375 g (3 g piperacillin/0.375 g tazobactam) every 6 hours intravenously (IV).
Alternatively: 4.5 g (4 g piperacillin/0.5 g tazobactam) every 6 or 8 hours IV.
The choice between 3.375 g and 4.5 g, and the dosing interval (6 vs. 8 hours), depends on the severity of infection, the suspected pathogens, and local susceptibility patterns. For severe infections or those caused by less susceptible organisms, the 4.5 g dose every 6 hours is often preferred.
**Maximum Dose:** Not explicitly defined by a total drug amount, but doses higher than 4.5 g every 6 hours are not typically recommended due to increased risk of adverse effects.
## Pediatric Dosing
**Neonates and Infants < 2 months:** Dosing is highly variable and often based on expert recommendation or specific protocols due to immature renal and hepatic function. A common approach involves weight-based dosing (e.g., 75-100 mg piperacillin component per kg per day divided every 6-8 hours IV), adjusted for gestational and chronological age.
**Children > 2 months to 12 years:**
* For uncomplicated infections: 100 mg piperacillin component/12.5 mg tazobactam component per kg per day divided every 6 hours IV.
* For complicated infections or *Pseudomonas aeruginosa* infections: 300 mg piperacillin component/37.5 mg tazobactam component per kg per day divided every 6 hours IV.
**Maximum Dose (Pediatric):** Typically 4.5 g per dose, regardless of weight, though the piperacillin component generally should not exceed 16 g per day.
## Dose Adjustments
**Renal Impairment (CrCl < 20 mL/min):**
* For 3.375 g every 6 hours: Administer 2.25 g every 8 hours.
* For 4.5 g every 6 hours: Administer 3.375 g every 8 hours.
* For 4.5 g every 8 hours: Administer 2.25 g every 12 hours.
Doses may need further adjustment with intermittent hemodialysis or continuous renal replacement therapy (CRRT).
**Hepatic Impairment:** No specific dose adjustment is typically required, but caution is advised as liver impairment can affect drug clearance.
## Contraindications
* Hypersensitivity to piperacillin, tazobactam, other penicillins, cephalosporins, or beta-lactams.
* History of cholestatic jaundice/hepatic dysfunction associated with piperacillin/tazobactam therapy.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, rash, headache, insomnia, pruritus, increased liver enzymes (AST, ALT), eosinophilia, positive Coombs test.
* **Serious:** *Clostridioides difficile*-associated diarrhea (CDAD), hypersensitivity reactions (including anaphylaxis), seizures (especially with high doses or renal impairment), hematologic abnormalities (neutropenia, thrombocytopenia), interstitial nephritis, hepatitis.
## Key Drug Interactions
* **Probenecid:** May decrease renal clearance of piperacillin, leading to increased serum concentrations and potential toxicity.
* **Aminoglycosides:** Concurrent administration may lead to physical or chemical inactivation. However, in severe infections, especially with *Pseudomonas aeruginosa*, they are often co-administered, but should be administered separately.
* **Warfarin:** May decrease the effect of warfarin, increasing the risk of bleeding. Monitor INR closely.
* **Neuromuscular blocking agents:** Penicillins may potentiate neuromuscular blockade.
* **Methotrexate:** Penicillins may decrease methotrexate clearance, leading to increased toxicity.
* **Bacteriostatic antibiotics:** May antagonize the bactericidal effect of piperacillin/tazobactam.
## Monitoring
* Renal function (BUN, creatinine)
* Liver function tests (AST, ALT, bilirubin)
* Complete blood count (CBC) with differential, especially with prolonged therapy
* Electrolytes
* Signs and symptoms of infection
* Signs and symptoms of hypersensitivity reactions
* Signs and symptoms of CDAD
## Clinical Pearls
* Dosing is based on the piperacillin component. The ratio of piperacillin to tazobactam is fixed (8:1).
* Duration of therapy should be guided by clinical response, pathogen susceptibility, and institutional guidelines.
* Tazobactam broadens the spectrum of piperacillin by inhibiting many beta-lactamases.
* Infusion-related reactions (e.g., phlebitis, pain at injection site) can occur. Administer as a slow IV infusion over at least 30 minutes. Rapid infusion may increase the risk of seizures.
* For patients with severe renal impairment, consider using the 3.375 g formulation or adjusting the 4.5 g dose to avoid excessively large volumes.
* The risk of neutropenia and thrombocytopenia increases with prolonged therapy (> 10 days).
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*This information is intended for clinical pharmacists and should not replace a thorough review of the official prescribing information and patient-specific factors. Always verify current prescribing information with the manufacturer's package insert or a reliable drug information resource.*
