Aztreonam

# Aztreonam ## Overview - **Classification**: Monobactam antibiotic - **Mechanism**: Inhibits bacterial cell wall synthesis by binding specifically to penicillin-binding protein 3 (PBP-3) of Gram-negative aerobic bacteria. ## Primary Indications 1. **Serious Gram-negative Infections** - Including complicated UTIs, lower respiratory tract, intra-abdominal, septicemia, gynecologic, skin & soft tissue infections. 2. **Febrile Neutropenia** - Often used in combination with other agents. 3. **Penicillin Allergy** - Alternative for Gram-negative coverage in patients with a history of penicillin hypersensitivity. ## Adult Dosing ### Standard Dosing **Moderate to Severe Infections** - **Dose**: **1-2 g** - **Frequency**: Every **8-12 hours** - **Route**: IV or IM - **Duration**: Varies based on infection type and severity. **Life-threatening Infections (e.g., Septicemia, Pseudomonas infections)** - **Dose**: **2 g** - **Frequency**: Every **6-8 hours** - **Route**: IV **Cystic Fibrosis (Severe pulmonary infections)** - **Dose**: **50 mg/kg** up to **2 g** - **Frequency**: Every **6-8 hours** - **Maximum**: **8 g/day** ### Dose Adjustments - **Renal Impairment**: - CrCl **30-10 mL/min**: Initial dose, then **half** of usual maintenance dose at usual intervals. - CrCl **<10 mL/min**: Initial dose, then **one-quarter** of usual maintenance dose at usual intervals. - Hemodialysis: Administer **one-eighth** of initial dose after each dialysis session. - **Hepatic Impairment**: No specific dose adjustment necessary. - **Elderly Patients**: Adjust dose based on renal function. ## Pediatric Dosing ### Neonates (0-28 days) - **Weight < 1200 g, 0-7 days**: **30 mg/kg/dose** every **12 hours** - **Weight < 1200 g, 8-28 days**: **30 mg/kg/dose** every **8 hours** - **Weight 1200-2000 g, 0-7 days**: **30 mg/kg/dose** every **8-12 hours** - **Weight 1200-2000 g, 8-28 days**: **30 mg/kg/dose** every **6-8 hours** - **Weight > 2000 g, 0-7 days**: **30 mg/kg/dose** every **8 hours** - **Weight > 2000 g, 8-28 days**: **30 mg/kg/dose** every **6 hours** - **Route**: IV - **Special Notes**: Dosing intervals extended due to immature renal function. ### Infants (1-12 months) - **Dose**: **30 mg/kg/dose** - **Frequency**: Every **6-8 hours** - **Route**: IV - **Maximum**: Do not exceed **120 mg/kg/day** (max **8 g/day**). ### Children (1-12 years) - **Dose**: **30 mg/kg/dose** - **Frequency**: Every **6-8 hours** - **Route**: IV - **Maximum**: Do not exceed **120 mg/kg/day** (max **8 g/day**). - **Considerations**: Max single dose of **2 g**. ### Adolescents (13-18 years) - **Dose**: Use **adult dosing regimens**. - **Route**: IV or IM - **Maximum**: **8 g/day**. ## Safety Information ### Contraindications - **Absolute**: Known serious hypersensitivity to aztreonam. ### Common Adverse Effects - **Common (1-10%)**: Diarrhea, Nausea, Vomiting, Rash, Injection site reactions (phlebitis, discomfort). - **Less Common (<1%)**: Increased LFTs, Eosinophilia, Thrombocytopenia, Pseudomembranous colitis. - **Serious but Rare**: Anaphylaxis, angioedema, severe dermatologic reactions (e.g., SJS, TEN), Clostridium difficile-associated diarrhea (CDAD). ### Key Drug Interactions - **Aminoglycosides**: May have synergistic effect against some Gram-negative bacteria. - **Warfarin**: May potentiate anticoagulant effect; monitor INR closely. - **Other Beta-lactamases Inducers**: May reduce aztreonam efficacy in some cases; clinical significance is usually low. ## Monitoring & Follow-up - **Before Treatment**: Obtain culture & sensitivity, assess renal function (CrCl). - **During Treatment**: Monitor renal function (BUN/Cr) and LFTs if prolonged therapy or underlying dysfunction. - **Clinical Signs**: Watch for signs of superinfection (e.g., oral candidiasis, CDAD), hypersensitivity reactions, or injection site issues. ## Clinical Pearls - 💡 **Penicillin Allergy Safe**: Aztreonam is a monobactam and generally safe for patients with IgE-mediated penicillin allergies due to its distinct chemical structure. - 💡 **Gram-Negative Only**: Provides activity exclusively against Gram-negative aerobic bacteria. It lacks Gram-positive and anaerobic coverage. - 💡 **Infusion Rate**: Administer IV infusions slowly over **20-60 minutes** to minimize local site reactions. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.