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# Aztreonam Avibactam (avycaz)
## Overview
Aztreonam-avibactam is a fixed-dose combination of a monobactam antibiotic and a non-beta-lactam beta-lactamase inhibitor. Note: **"Avycaz" is the brand name for Ceftazidime-Avibactam.** There is currently **no FDA-approved combination product marketed as "Aztreonam-Avibactam"** under the trade name Avycaz. Aztreonam is often used *in combination* with Ceftazidime-Avibactam (off-label) to cover metallo-beta-lactamase (MBL) producing organisms.
## Primary Indications
Primarily used for the treatment of complicated intra-abdominal infections (cIAI) and complicated urinary tract infections (cUTI), including pyelonephritis, caused by susceptible Gram-negative organisms, including multidrug-resistant strains like MBL producers.
## Adult Dosing
* **Standard dose:** 2.5 g (2 g ceftazidime / 0.5 g avibactam) IV every 8 hours.
* **Infusion time:** Administer over 2 hours.
* **Duration:** Typically 7–14 days depending on infection severity and site.
## Pediatric Dosing
Safety and efficacy have not been established in patients <18 years of age in the context of the combined product. Dosing should be determined by institutional infectious disease specialists and pediatric pharmacology protocols.
## Dose Adjustments
* **Renal Impairment:** Requires significant dose reduction based on CrCl (Cockcroft-Gault).
* CrCl 31–50 mL/min: 1.25 g every 8 hours.
* CrCl 16–30 mL/min: 0.94 g every 12 hours.
* CrCl 6–15 mL/min: 0.94 g every 24 hours.
* CrCl ≤5 mL/min: 0.94 g every 48 hours.
* **Hepatic Impairment:** No dosage adjustment recommended.
## Contraindications
* Known hypersensitivity to ceftazidime, avibactam, or any component of the formulation.
* History of severe hypersensitivity (e.g., anaphylaxis) to any other beta-lactam antibacterial drug.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, constipation, headache, dizziness.
* **Serious:** *Clostridioides difficile*-associated diarrhea (CDAD), hypersensitivity reactions, seizures (rare, mostly in renal impairment), and elevated liver enzymes.
## Key Drug Interactions
* **Probenecid:** May inhibit renal tubular secretion of ceftazidime, increasing serum concentrations.
* **Antibiotic synergy:** May have additive effects with other agents (e.g., aminoglycosides), but no specific high-risk metabolic interactions.
## Monitoring
* **Renal Function:** Monitor CrCl throughout therapy, especially in elderly or unstable patients.
* **Clinical Response:** Monitor for signs of persistent infection or new-onset diarrhea/superinfection.
* **Neurological:** Monitor for CNS effects if renal function is compromised.
## Clinical Pearls
* **MBL Coverage:** In the presence of metallo-beta-lactamase producing organisms, aztreonam is often added to ceftazidime-avibactam. This is because aztreonam is stable against MBLs, whereas ceftazidime-avibactam is not.
* **Stability:** Once reconstituted, the solution must be used promptly or refrigerated/frozen per specific manufacturer stability data.
* **Prescribing Note:** Always clarify if the order is for the fixed-dose combination (Ceftazidime-Avibactam) or the combination of two separate agents (Aztreonam + Ceftazidime-Avibactam).
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**Disclaimer:** This information is for educational purposes only. Clinical practice varies; always consult your institution’s antimicrobial stewardship program, local antibiograms, and the most current FDA-approved prescribing information (package insert) before administering medication.
