Aztreonam Dosage and Treatment Guidelines for Gram-Negative Infections
The recommended dosage of aztreonam for treating infections caused by susceptible gram-negative bacteria is 1-2 grams intravenously every 6-8 hours, with duration typically ranging from 7-14 days depending on infection severity. 1
Dosing Recommendations Based on Infection Severity
Aztreonam dosing should be tailored according to the severity of infection:
- Mild to moderate infections: 1 gram IV every 8-12 hours
- Moderately severe systemic infections: 1-2 grams IV every 8-12 hours
- Severe systemic or life-threatening infections: 2 grams IV every 6-8 hours 2
For Pseudomonas aeruginosa infections specifically, the higher dosage of 2 grams every 6-8 hours is recommended upon initiation of therapy due to the serious nature of these infections. 2
Special Patient Populations
Renal Impairment
- For patients with creatinine clearance between 10-30 mL/min/1.73m², the dosage should be halved after an initial loading dose of 1-2 grams
- For severe renal failure (creatinine clearance <10 mL/min/1.73m²), give the usual initial dose followed by maintenance doses at one-fourth the usual dose at the fixed interval 2
- For hemodialysis patients, administer one-eighth of the initial dose after each hemodialysis session in addition to maintenance doses 2
Pediatric Patients
- For mild to moderate infections: 30 mg/kg every 8 hours
- For moderate to severe infections: 30 mg/kg every 6-8 hours
- Maximum recommended dose: 120 mg/kg/day 2
Spectrum of Activity and Clinical Applications
Aztreonam has a unique and specific spectrum of activity:
- Highly effective against aerobic gram-negative bacteria including most Enterobacteriaceae and Pseudomonas aeruginosa
- Particularly effective against Haemophilus influenzae and Serratia marcescens
- No activity against gram-positive bacteria or anaerobes 1
This specific spectrum makes aztreonam particularly valuable in:
- Treating patients with severe penicillin allergies as an alternative to β-lactam antibiotics 1
- Treating infections caused by multidrug-resistant gram-negative organisms, especially when combined with other agents 1
Treatment Duration
The duration of therapy depends on the severity of infection:
- Generally, continue aztreonam for at least 48 hours after the patient becomes asymptomatic or evidence of bacterial eradication has been obtained
- Persistent infections may require treatment for several weeks 2
- For most bacterial skin and soft tissue infections, treatment for 7-14 days is recommended 3
Combination Therapy Considerations
When treating mixed infections or those of unknown etiology, combination therapy is recommended:
- For coverage of gram-positive organisms, add appropriate agents since aztreonam lacks activity against these pathogens 4
- For metallo-β-lactamases-producing CRE infections, combine with ceftazidime-avibactam for synergistic effect 1
- Aztreonam is compatible with many antibiotics in IV solutions, including clindamycin phosphate, gentamicin sulfate, tobramycin sulfate, and cefazolin sodium 2
Clinical Efficacy
Aztreonam has demonstrated high clinical efficacy in:
- Urinary tract infections
- Lower respiratory tract infections
- Intra-abdominal infections
- Skin and soft tissue infections
- Septicemia caused by susceptible gram-negative organisms 4, 5
Important Considerations and Potential Pitfalls
Coverage gaps: When using aztreonam as monotherapy, remember it lacks activity against gram-positive and anaerobic bacteria, requiring combination therapy for mixed infections 4
Incompatibility: Aztreonam is incompatible with nafcillin sodium, cephradine, and metronidazole; avoid these combinations 2
Dosing frequency: Due to its relatively short half-life (<2 hours), more frequent dosing (every 6-8 hours) is necessary for moderate to severe infections 6
Pseudomonal infections: While effective against P. aeruginosa, higher doses are required, and combination therapy with aminoglycosides may be synergistic for difficult cases 7
Aztreonam's unique properties make it particularly valuable for treating serious gram-negative infections, especially in patients with β-lactam allergies, while minimizing disruption to the normal anaerobic gut flora.