AZACTAM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for AZACTAM (AZACTAM).
Aztreonam is a monobactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), specifically PBP-3 in Gram-negative bacteria, leading to cell death. It is active against aerobic Gram-negative bacilli and has no activity against Gram-positive or anaerobic organisms.
| Metabolism | Aztreonam is primarily metabolized by hydrolysis of the beta-lactam ring to an inactive metabolite. Approximately 60-70% of the dose is excreted unchanged in the urine, with a small amount undergoing hepatic metabolism. |
| Excretion | Primarily renal (unchanged drug): 60-75% excreted in urine within 8 hours; 10-15% biliary/fecal. Dosage adjustment required in renal impairment. |
| Half-life | Terminal elimination half-life: 1.7-2.2 hours in normal renal function. Prolonged to 6-9 hours in end-stage renal disease; not appreciably removed by hemodialysis. |
| Protein binding | Approximately 40% bound to serum proteins (primarily albumin). Binding is concentration-independent. |
| Volume of Distribution | Steady-state Vd: 0.2-0.4 L/kg, extravascular distribution moderate; adequate penetration into blister fluid, bile, peritoneal fluid, and CSF only with inflamed meninges. |
| Bioavailability | Intramuscular: ~100% bioavailability. Intravenous: 100%. Not orally bioavailable. |
| Onset of Action | Intravenous: clinical response within 1-2 hours. Intramuscular: peak serum levels in 60-90 min with therapeutic effect shortly thereafter. |
| Duration of Action | Duration of bactericidal activity: 6-8 hours after intravenous dose; sustained slightly longer with intramuscular administration. Dosing interval depends on renal function. |
1-2 g intravenously or intramuscularly every 6-8 hours; maximum 8 g/day.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 10-30 mL/min: 500 mg-1 g every 12 hours; CrCl <10 mL/min: 500 mg-1 g every 24 hours. |
| Liver impairment | No adjustment required for hepatic impairment. |
| Pediatric use | Infants >1 month and children: 30-50 mg/kg intravenously every 6-8 hours; maximum 6 g/day. |
| Geriatric use | Dose based on renal function; consider age-related creatinine clearance decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for AZACTAM (AZACTAM).
| Breastfeeding | Aztreonam is excreted in human milk in low concentrations (M/P ratio ~0.3). Consider developmental benefits of breastfeeding vs. potential for infant diarrhea or sensitization. |
| Teratogenic Risk | Pregnancy Category B. No evidence of teratogenicity in animal studies; no adequate human studies in first trimester. Use only if clearly needed. Fetal risk cannot be excluded. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to aztreonam or any component of the formulation","Patients with immediate-type hypersensitivity reactions (e.g., anaphylaxis) to other beta-lactams (use with caution)"]
| Precautions | ["Hypersensitivity reactions (including anaphylaxis) may occur, especially in patients with penicillin or cephalosporin allergies","Pseudomembranous colitis (Clostridium difficile-associated diarrhea) has been reported","Renal impairment requires dose adjustment; monitor renal function","Seizures and neurotoxicity can occur, especially in patients with renal impairment or high doses","Superinfection with resistant organisms may occur with prolonged use"] |
| Food/Dietary | No specific food interactions; maintain adequate hydration. Avoid alcohol: although no disulfiram-like reaction confirmed, alcohol may increase risk of adverse effects (headache, nausea). Take on empty stomach for optimal absorption (oral formulation not available; IV/IM only). |
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| Monitor maternal renal function, hepatic function, and signs of hypersensitivity. Fetal monitoring per standard obstetric care. |
| Fertility Effects | No known adverse effects on fertility based on animal studies. |
| Clinical Pearls | Aztreonam is a monobactam antibiotic with activity against aerobic Gram-negative bacilli, including Pseudomonas aeruginosa. It is not active against Gram-positive or anaerobic bacteria. Cross-reactivity with beta-lactam antibiotics is low but not zero; use caution in patients with immediate hypersensitivity to penicillins or cephalosporins. Administer IV over 20-60 minutes or IM deep into large muscle. Renal dose adjustment required (CrCl <30 mL/min). Can be used in penicillin-allergic patients as an alternative. Monitor for seizures in patients with renal impairment or those on high doses. |
| Patient Advice | Take this medication exactly as prescribed, even if you feel better. · Do not stop taking antibiotics without consulting your doctor. · If you miss a dose, take it as soon as possible unless it is close to the next dose. · Contact your doctor if you experience severe diarrhea, rash, or difficulty breathing. · This medication may cause injection site pain or redness; inform your healthcare provider if severe. · Inform your doctor about all medical conditions, especially kidney disease and allergies to antibiotics. |