What is the spectrum of activity and typical use of Ceftazidime (Ceftazidime) and Avibactam (Avibactam) in patients with severe or complicated infections, including those with impaired renal function or a history of allergy to cephalosporins (Cephalosporins) or penicillins (Penicillins)?

Ceftazidime-Avibactam: Spectrum and Clinical Use

Ceftazidime-avibactam is a carbapenem-sparing agent specifically indicated for multidrug-resistant Gram-negative infections, particularly those caused by ESBL-producing Enterobacteriaceae, KPC-producing organisms, and OXA-48 producers, but it requires metronidazole addition for intra-abdominal infections and is ineffective against metallo-β-lactamase producers. 1

Spectrum of Activity

Organisms Covered

• ESBL-producing Enterobacteriaceae (including E. coli and Klebsiella pneumoniae) 1, 2
• KPC-producing Enterobacteriaceae (KPC-2 and KPC-3) 1, 3, 4
• OXA-48 carbapenemase producers 3, 4, 5
• AmpC β-lactamase-producing organisms 4, 2, 6
• Multidrug-resistant Pseudomonas aeruginosa (including some AmpC-producing strains) 1, 4, 6

Critical Gaps in Coverage

• No activity against metallo-β-lactamases (NDM, VIM, IMP producers) 3, 4, 6
• No anaerobic coverage (requires metronidazole for intra-abdominal infections) 1, 4
• No Gram-positive coverage (no MRSA or enterococcal activity) 4
• Limited activity against some Bacteroides species 1
• Intrinsic resistance in Acinetobacter species due to OXA-type carbapenemases not inhibited by avibactam 4

Approved Indications and Dosing

Standard Dosing

• Ceftazidime 2 g-avibactam 0.5 g IV every 8 hours as a 2-hour infusion 2, 7
• For complicated intra-abdominal infections: must combine with metronidazole 1, 4
• For hospital-acquired/ventilator-associated pneumonia: add vancomycin or linezolid for MRSA coverage 4

Renal Dosing Adjustments (Critical)

Monitor creatinine clearance at least daily as both ceftazidime and avibactam are renally eliminated 8, 7

• CrCl 31-50 mL/min: 1 g-0.25 g IV every 8 hours 8, 9
• CrCl 16-30 mL/min: 0.75 g-0.1875 g IV every 12 hours 8, 9
• CrCl 6-15 mL/min: 0.75 g-0.1875 g IV every 24 hours 8, 9
• End-stage renal disease on hemodialysis: Load with 0.75 g-0.1875 g, then 0.375 g-0.09375 g IV every 48 hours (administer after hemodialysis on dialysis days, as approximately 55% is removed during a 4-hour session) 8

Common pitfall: Failure to adjust dosing as renal function improves can lead to subtherapeutic levels; the modified dosage adjustments (50% increase in total daily dose for moderate/severe impairment) were specifically designed to prevent this 9

Clinical Use Algorithm

When to Use Ceftazidime-Avibactam

For Hospital-Acquired/Healthcare-Associated Infections with Risk Factors for Resistance:

• Prior IV antibiotic use within 90 days 4
• ICU with >10-20% carbapenem-resistant Gram-negative isolates 4
• Septic shock or ARDS at presentation 4
• ≥5 days hospitalization prior to infection 4
• Acute renal replacement therapy 4

For Documented Resistant Organisms:

• KPC, ESBL, AmpC, or OXA-48 producers: Use ceftazidime-avibactam monotherapy (plus metronidazole for IAI) 3
• Unknown carbapenemase type in critically ill patient: Start ceftazidime-avibactam plus aztreonam empirically until susceptibilities return 3

When NOT to Use Ceftazidime-Avibactam

• Aspiration pneumonia (lacks anaerobic coverage; use ampicillin-sulbactam or piperacillin-tazobactam instead) 4
• Documented metallo-β-lactamase producers (NDM, VIM, IMP) as monotherapy—will fail 3, 4
• Community-acquired infections without resistance risk factors (use narrower-spectrum agents) 1

Special Combination: Ceftazidime-Avibactam Plus Aztreonam

For metallo-β-lactamase producers (NDM, VIM, IMP), the combination of ceftazidime-avibactam plus aztreonam demonstrates significantly lower 30-day mortality (HR 0.37,95% CI 0.13-0.74) compared to other regimens 1, 3

Mechanism: Avibactam protects aztreonam from degradation by other β-lactamases while aztreonam remains active against MBL producers 1, 3

Critical pitfall: Never use ceftazidime-avibactam alone for NDM-producing organisms—it will fail due to lack of MBL inhibition 3

Allergy Considerations

For patients with cephalosporin or penicillin allergies, ceftazidime-avibactam is contraindicated due to cross-reactivity risk 1. Alternative options include:

• Fluoroquinolones (ciprofloxacin plus metronidazole) for mild infections without resistance risk 1
• Aztreonam (a monobactam with no cross-reactivity) for Gram-negative coverage 1
• Aminoglycosides plus metronidazole (though aminoglycosides reserved for combination therapy due to toxicity) 1

Safety Profile

• Hepatic safety: No significant liver enzyme elevation observed; equivalent hepatic safety to comparator regimens 10
• Renal monitoring: Essential due to renal elimination; adverse events related to impaired renal function occurred in 8.3% of patients 8, 5
• Overall tolerability: Safety profile consistent with ceftazidime alone and typical of injectable cephalosporins 6

Resistance Development and Stewardship

• Resistance emergence: Occurs in 3.7-10.4% of treated patients, with renal replacement therapy as an independent predictor (p=0.009) 1, 4
• Stewardship principle: Reserve ceftazidime-avibactam for documented resistant organisms or high-risk empiric situations to preserve carbapenem alternatives 1, 2
• De-escalation: When cultures return, narrow to pathogen-directed therapy if possible 1

Clinical Outcomes

• 30-day mortality: 8.3% in OXA-48 CPE infections 5
• Clinical cure rates: 62.5-91.2% across indications 2, 5
• Microbiological success: 70.5% in complicated UTIs, comparable to carbapenems 2
• Recurrence risk: 35% within 90 days of treatment completion 5