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# Aztreonam/Avibactam
## Overview
Aztreonam-avibactam is a fixed-dose combination of a monobactam antibiotic and a β-lactamase inhibitor. It is designed to overcome resistance mediated by metallo-β-lactamases (MBLs), such as NDM-1, which hydrolyze most other β-lactams. *Note: Commercially available as Emblaveo (EU). "Avycaz" is the brand name for Ceftazidime/Avibactam; do not confuse these.*
## Primary Indications
Treatment of complicated intra-abdominal infections (cIAI), complicated urinary tract infections (cUTI), including pyelonephritis, and hospital-acquired pneumonia (HAP), including ventilator-associated pneumonia (VAP), caused by aerobic Gram-negative organisms where other options are limited or ineffective.
## Adult Dosing
* **Standard Regimen:** 500 mg (aztreonam) / 133 mg (avibactam) administered as an intravenous infusion over 2 hours, every 6 or 8 hours depending on severity and renal function.
* **Total Daily Dose:** Usually 2 g/532 mg per day, though dosing must be individualized based on local institutional protocols and creatinine clearance.
## Pediatric Dosing
Safety and efficacy in pediatric patients (<18 years) are not well-established. Use should be avoided unless no alternative therapy exists and the benefit outweighs the risk. Dosing in this population lacks standardized guidelines; use only under infectious disease expert supervision.
## Dose Adjustments
* **Renal Impairment:** Requires significant dose reduction or interval extension based on estimated glomerular filtration rate (eGFR).
* **Hepatic Impairment:** No specific dosage adjustment usually required, but use with caution.
* **Renal Replacement Therapy:** Dose supplementation is typically required post-dialysis, as both components are removed by hemodialysis. Follow specific manufacturer or institutional pharmacy guidelines for supplemental dosing.
## Contraindications
* Known severe hypersensitivity (e.g., anaphylaxis) to aztreonam, avibactam, or any component of the formulation.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, dizziness, headache.
* **Serious:** *Clostridioides difficile*-associated diarrhea (CDAD), hypersensitivity reactions, elevated transaminases, and potential for seizures (specifically with high-dose aztreonam).
## Key Drug Interactions
* **Probenecid:** May increase serum concentrations of aztreonam by inhibiting renal excretion; avoid concomitant use.
* **Overlapping Toxicity:** Use caution with other agents that may cause renal impairment or lower the seizure threshold.
## Monitoring
* **Renal Function:** Monitor serum creatinine and eGFR closely; adjust doses promptly as renal function changes.
* **Clinical Efficacy:** Monitor for resolution of infection symptoms.
* **Safety:** Monitor for signs of *C. difficile* infection and hypersensitivity reactions during infusion.
## Clinical Pearls
* **MBL Activity:** This agent is a "last-resort" therapy specifically for MBL-producing Gram-negative bacteria. Reserve use for documented MBL-mediated resistance to preserve efficacy.
* **Spectrum:** It does not cover Gram-positive organisms or anaerobes; combination therapy with agents like metronidazole is often necessary for polymicrobial infections (e.g., cIAI).
* **Infusion Compatibility:** Verify Y-site compatibility before administration; aztreonam is incompatible with several common intravenous solutions and medications.
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*Disclaimer: This information is for educational purposes and does not replace professional clinical judgment. Prescribers must verify current prescribing information, institutional protocols, and patient-specific factors before administration.*
