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

Aztreonam Dosage Recommendations

Standard Adult Dosing (Normal Renal Function)

For adults with normal renal function, aztreonam should be dosed at 1-2 g every 8 hours for most systemic infections, with 2 g every 6-8 hours reserved for severe or life-threatening infections, particularly those caused by Pseudomonas aeruginosa. 1

Infection-Specific Dosing

• Urinary tract infections: 500 mg to 1 g every 8-12 hours 1
• Moderately severe systemic infections: 1-2 g every 8-12 hours 1
• Severe systemic or life-threatening infections: 2 g every 6-8 hours 1
• Hospital-acquired pneumonia with antipseudomonal coverage: 2 g IV every 8 hours 2
• Complicated intra-abdominal infections: 1-2 g every 6-8 hours 2

Route of Administration

• Intravenous route is recommended for single doses >1 g or for patients with bacterial septicemia, localized parenchymal abscess, peritonitis, or other severe systemic infections 1
• Intramuscular administration is acceptable for doses ≤1 g in less severe infections 1

---

Dosing in Renal Impairment

Aztreonam clearance correlates directly with creatinine clearance, requiring dose reduction in patients with renal dysfunction. 3, 4

Creatinine Clearance 10-30 mL/min/1.73 m²

• Give full loading dose (1 g or 2 g) initially 1
• Reduce maintenance dose to 50% of the usual dose at the standard interval (every 6,8, or 12 hours) 1
• Example: If normal dose is 2 g every 8 hours, give 2 g loading dose, then 1 g every 8 hours 1

Creatinine Clearance <10 mL/min/1.73 m² (Including Hemodialysis)

• Give full loading dose (500 mg, 1 g, or 2 g) initially 1
• Reduce maintenance dose to 25% of the usual initial dose at the standard interval 1
• For hemodialysis patients: Give an additional one-eighth of the initial dose after each hemodialysis session 1
• Example: If normal dose is 2 g every 8 hours, give 2 g loading dose, then 500 mg every 8 hours, plus 250 mg after each dialysis 1

Estimating Creatinine Clearance

When only serum creatinine is available, use the Cockcroft-Gault equation 1:

• Males: CrCl = [weight (kg) × (140 - age)] / [72 × serum creatinine (mg/dL)]
• Females: 0.85 × male calculation 1

---

Duration of Therapy

• Continue aztreonam for at least 48 hours after the patient becomes asymptomatic or evidence of bacterial eradication is obtained 1, 5
• Persistent infections may require several weeks of treatment 1, 5
• For complicated intra-abdominal infections, 4-7 days is typically adequate unless source control is difficult 5

---

Pharmacokinetic Considerations

Key Parameters in Normal Renal Function

• Half-life: 1.5-2.1 hours 6, 7
• Volume of distribution: 0.16-0.18 L/kg (approximates extracellular fluid volume) 3, 7
• Protein binding: ~30% 3
• Renal excretion: 60-70% unchanged in urine 7

Extended Infusions

• Extended infusions may be appropriate for pharmacokinetic/pharmacodynamic optimization, particularly for time-dependent killing 2
• Standard infusion times are adequate for most clinical scenarios 1

---

Special Populations

Elderly Patients

• Renal function is the major determinant of dosing in elderly patients 1
• Serum creatinine may not accurately reflect renal status; estimate creatinine clearance and adjust dose accordingly 1
• Elderly patients commonly have diminished renal function requiring dose reduction 1

Pediatric Patients (Age 1 Month to 12 Years)

• Mild to moderate infections: 30 mg/kg every 8 hours 1, 2
• Moderate to severe infections: 30 mg/kg every 6-8 hours 1, 2
• Maximum daily dose: 120 mg/kg/day 1, 2
• Administer intravenously; insufficient data for intramuscular use in pediatrics 1

---

Clinical Pearls and Pitfalls

Common Pitfalls to Avoid

• Do not use doses smaller than indicated in the dosing table, as this may lead to treatment failure 1
• Do not skip the loading dose in renal impairment—full loading doses are essential to achieve therapeutic levels quickly 1
• Remember post-dialysis supplementation in hemodialysis patients, as 60-70% of aztreonam is removed by dialysis 7

Monitoring

• Monitor renal function throughout therapy, particularly in patients with fluctuating renal status 3
• Aztreonam clearance increases with improving renal function, potentially requiring dose adjustment 3
• No significant drug accumulation occurs with multiple dosing when appropriately adjusted for renal function 3

Combination Therapy

• Aztreonam has no activity against gram-positive or anaerobic bacteria 7, 6, 8
• Concurrent therapy with other antimicrobials is recommended for empiric treatment of seriously ill patients at risk for gram-positive or anaerobic infections 6, 8
• Aztreonam acts synergistically with aminoglycosides against Pseudomonas aeruginosa and gentamicin-resistant gram-negative rods 7