What is the recommended dosage of Aztreonam (Aztreonam) for adults with normal renal function and those with impaired renal function?

Aztreonam Dosage Recommendations

For adults with normal renal function, the recommended aztreonam dosage is 1-2 g every 8-12 hours for moderate infections, and 2 g every 6-8 hours for severe systemic or life-threatening infections, especially those caused by Pseudomonas aeruginosa. 1

Standard Dosing for Adults with Normal Renal Function

The FDA-approved dosing guidelines for aztreonam in adults with normal renal function are as follows:

• Urinary tract infections: 500 mg or 1 g every 8 or 12 hours 1
• Moderately severe systemic infections: 1 g or 2 g every 8 or 12 hours 1
• Severe systemic or life-threatening infections: 2 g every 6 or 8 hours 1

For Pseudomonas aeruginosa infections, which are often serious in nature, a dosage of 2 g every 6 or 8 hours is recommended, at least upon initiation of therapy 1, 2

Renal Impairment Dosing Adjustments

Aztreonam requires significant dose adjustments in patients with renal impairment:

• For patients with creatinine clearance between 10-30 mL/min/1.73 m²: The dosage should be halved after an initial loading dose of 1 g or 2 g 1
• For patients with severe renal failure (creatinine clearance <10 mL/min/1.73 m²): Give the usual initial dose (500 mg, 1 g, or 2 g), then reduce maintenance dose to one-fourth of the usual initial dose at the usual fixed interval (6,8, or 12 hours) 1
• For hemodialysis patients: In addition to the maintenance doses, one-eighth of the initial dose should be given after each hemodialysis session for serious or life-threatening infections 1, 3

When only serum creatinine is available, the following formula can be used to estimate creatinine clearance:

• Males: Clcr = [weight (kg) × (140−age)] / [72 × serum creatinine (mg/dL)]
• Females: Clcr = 0.85 × above value 1

Elderly Patients

• Renal status is a major determinant of dosage in elderly patients, who often have diminished renal function 1
• Serum creatinine may not accurately reflect renal status in elderly patients; therefore, estimates of creatinine clearance should be obtained and appropriate dosage modifications made 1, 3
• In a study of elderly patients (average age 72 years) with diminished renal function, aztreonam was found to be safe when dosed according to creatinine clearance 3

Route of Administration

• The intravenous route is recommended for patients requiring single doses greater than 1 g or those with bacterial septicemia, localized parenchymal abscess, peritonitis, or other severe systemic or life-threatening infections 1
• Intramuscular administration is an option for less severe infections requiring doses of 1 g or less 1, 4

Duration of Therapy

• Generally, aztreonam should be continued for at least 48 hours after the patient becomes asymptomatic or evidence of bacterial eradication has been obtained 1
• Persistent infections may require treatment for several weeks 1

Clinical Considerations

• Aztreonam has a strictly gram-negative aerobic spectrum, which limits its use as a single empiric agent 5, 6
• For serious infections where gram-positive or anaerobic pathogens may be present, concurrent initial therapy with other antimicrobial agents is recommended 5, 6
• The serum half-life of aztreonam in patients with normal renal function is 1.5 to 2.1 hours 5, 2
• Aztreonam is widely distributed in body tissues and fluids, with 60-70% excreted unchanged in the urine 2

By following these dosing recommendations and making appropriate adjustments for renal function, aztreonam can be safely and effectively administered to treat serious gram-negative infections while avoiding the nephrotoxicity associated with aminoglycosides.