## Orbital Cellulitis: First-Line Antibiotic Therapy ### Clinical Context Orbital cellulitis is a medical emergency requiring prompt broad-spectrum IV antibiotics. The condition is typically polymicrobial, with common pathogens including Staphylococcus aureus (including MRSA), Streptococcus species, and gram-negative organisms. ### Why Ceftriaxone + Vancomycin? **Key Point:** The combination of ceftriaxone (third-generation cephalosporin) and vancomycin is the gold standard first-line empirical regimen for orbital cellulitis. **High-Yield:** This combination provides: - **Ceftriaxone:** Excellent gram-negative coverage, good CNS penetration, covers sensitive gram-positive organisms - **Vancomycin:** Essential for MRSA coverage and resistant Streptococcus species ### Dosing Regimen | Drug | Dose | Frequency | Notes | |------|------|-----------|-------| | Ceftriaxone | 1–2 g | IV every 12 hours | Higher doses for severe infection | | Vancomycin | 15–20 mg/kg | IV every 8–12 hours | Adjust for renal function; monitor trough levels | ### Adjunctive Management 1. Identify and treat primary source (sinusitis, dacryocystitis, trauma, foreign body) 2. Imaging: CT/MRI orbit with contrast to rule out abscess 3. If abscess present → urgent surgical drainage + antibiotics 4. Corticosteroids may be considered in severe cases with significant edema (controversial) **Clinical Pearl:** Always obtain blood and orbital cultures before starting antibiotics if possible, but do NOT delay treatment for culture results. **Tip:** Switch to oral antibiotics (e.g., amoxicillin-clavulanate or fluoroquinolone) once clinical improvement is evident and the patient can tolerate oral intake—typically after 48–72 hours of IV therapy. Total duration: 2–3 weeks depending on source control. [cite:Orbit and Ocular Adnexa, Ophthalmology textbooks]
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