What is the recommended dosing of Aztreonam (Aztreonam) for an adult female with a Urinary Tract Infection (UTI) and Chronic Kidney Disease (CKD) stage 3A with moderate renal impairment?

Aztreonam Dosing for Adult Female with UTI and CKD 3A

For an adult female with UTI and CKD stage 3A (moderate renal impairment), aztreonam should be dosed at 1-2g IV every 8-12 hours with no dose adjustment required since CKD 3A typically has a creatinine clearance between 45-59 mL/min.

Understanding Aztreonam and Renal Dosing

Aztreonam is a monobactam antibiotic primarily used for gram-negative infections, including urinary tract infections. Its elimination is predominantly renal, making dose adjustments necessary in patients with significant renal impairment.

Dosing Based on Renal Function:

According to the FDA drug label for Aztreonam 1:

• Normal renal function: 500 mg to 1g every 8-12 hours for UTIs
• Moderate to severe UTIs: 1g every 8-12 hours
• Creatinine clearance 10-30 mL/min: Dose should be halved after an initial loading dose
• Creatinine clearance <10 mL/min: Maintenance dose should be one-fourth of the initial dose

Application to CKD 3A Patients

CKD stage 3A corresponds to a GFR/creatinine clearance of 45-59 mL/min, which is above the threshold (30 mL/min) where aztreonam dose adjustment becomes necessary.

For a female patient with UTI and CKD 3A:

• Initial dose: 1-2g IV (depending on severity)
• Maintenance dose: 1-2g IV every 8-12 hours
• No dose reduction required as the creatinine clearance is >30 mL/min

Monitoring Considerations

• Regularly assess renal function during therapy
• Watch for signs of drug accumulation (neurotoxicity, GI disturbances)
• Consider therapeutic drug monitoring in prolonged therapy

Clinical Efficacy in UTIs

Aztreonam has demonstrated good efficacy in complicated UTIs. Studies have shown:

• 64-87% clinical efficacy rate in complicated UTIs 2
• Particularly effective against gram-negative pathogens with an 87.1% eradication rate 2
• Effective even against multidrug-resistant gram-negative bacteria 3

Important Considerations

• If renal function deteriorates during treatment (creatinine clearance drops below 30 mL/min), dose adjustment will become necessary
• For severe infections, higher doses (2g every 8 hours) may be appropriate initially 1
• The correlation between aztreonam clearance and creatinine clearance is strong (r²=0.90), making renal function a reliable predictor of drug clearance 4

Common Pitfalls to Avoid

1. Failure to reassess renal function: CKD patients may experience fluctuations in renal function during infection/treatment
2. Underdosing: Insufficient dosing can lead to treatment failure, especially with resistant organisms
3. Overlooking drug interactions: While aztreonam has fewer drug interactions than many antibiotics, concomitant nephrotoxic drugs should be used cautiously

Population pharmacokinetic modeling supports the current dosing recommendations for patients with moderate renal impairment, with adequate probability of target attainment at the recommended doses 5.