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# Aztreonam-Avibactam
## Overview
Aztreonam-avibactam is a fixed-dose combination of a monobactam antibiotic and a non-beta-lactam beta-lactamase inhibitor. It is specifically designed to stabilize aztreonam against hydrolysis by metallo-beta-lactamases (MBLs), such as NDM-1, as well as serine beta-lactamases including KPC and ESBLs.
## Primary Indications
Treatment of complicated intra-abdominal infections (cIAI) and complicated urinary tract infections (cUTI), including pyelonephritis, caused by susceptible Gram-negative organisms, particularly when MBL-producing pathogens are suspected.
## Adult Dosing
The standard dosage is 500 mg (aztreonam) / 133.3 mg (avibactam) administered via intravenous infusion over 2 hours every 8 hours. The total daily dose of aztreonam should not exceed 1.5 g.
## Pediatric Dosing
Safety and efficacy in pediatric patients have not been established by the FDA/EMA for this specific combination product. Dosing should be based on institutional protocols or infectious disease consultation if off-label use is considered in life-threatening, multi-drug resistant infections.
## Dose Adjustments
Renal impairment requires significant adjustment. For patients with a CrCl < 50 mL/min, dosing frequency must be extended (e.g., every 12 or 24 hours) or the dose reduced per specific renal nomograms. Pharmacokinetic monitoring or infectious disease pharmacy consultation is strongly recommended due to the narrow therapeutic window for renal clearance.
## Contraindications
Hypersensitivity to aztreonam, avibactam, or any component of the formulation.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, constipation, elevated liver transaminases (ALT/AST), and headache. Serious risks include *Clostridioides difficile*-associated diarrhea and potential hypersensitivity reactions (though aztreonam has a lower cross-reactivity risk with penicillins/cephalosporins).
## Key Drug Interactions
Aztreonam is not a major inducer or inhibitor of CYP450 enzymes. Caution is advised with concomitant use of drugs that are substrates of OAT1/OAT3 transporters (e.g., probenecid), as these can increase exposure to aztreonam.
## Monitoring
Monitor renal function (SCr/CrCl) at baseline and throughout therapy. Conduct serial LFT monitoring if used longer than 7–14 days. If signs/symptoms of severe diarrhea occur, test for *C. difficile*.
## Clinical Pearls
* **MBL Activity:** This is one of the few therapeutic options for organisms producing MBLs (e.g., NDM, VIM, IMP).
* **Spectrum:** It does not cover Gram-positive organisms (e.g., *Staphylococcus, Enterococcus*) or anaerobes. In cIAI, it must be combined with an agent covering anaerobes (e.g., metronidazole).
* **Stability:** Ensure the infusion duration is strictly maintained at 2 hours to optimize time above the MIC (fT > MIC).
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**Educational Disclaimer:** This information is for educational purposes only. Prescribing information, renal adjustment nomograms, and local susceptibility data must be verified against current institutional guidelines and the official package insert (e.g., FDA/EMA prescribing information) before administration. Consult an infectious disease specialist or pharmacist for complex clinical decisions.
