What is the best course of treatment for a patient with a history of sinus infections, currently experiencing facial pain, congestion, and a runny nose, who has previously been prescribed Cephalexin (Keflex) (Cephalexin)?

Cephalexin Is Not Appropriate for Acute Bacterial Sinusitis

Cephalexin should not be prescribed for this patient's sinus infection because it lacks adequate coverage against Haemophilus influenzae, a major pathogen in acute bacterial sinusitis, with nearly 50% of strains producing β-lactamase that renders first-generation cephalosporins ineffective. 1

Why Cephalexin Fails in Sinusitis

First-generation cephalosporins like cephalexin have poor coverage against the three primary bacterial pathogens in acute sinusitis: Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1 While cephalexin may cover some S. pneumoniae strains, 90-100% of M. catarrhalis are β-lactamase producing, further limiting its utility. 1

The American Academy of Allergy, Asthma, and Immunology explicitly contraindicates first-generation cephalosporins for sinusitis based on inadequate H. influenzae coverage. 1

Recommended Treatment Instead

First-Line Antibiotic Options

For this patient with recurrent sinusitis and previous cephalexin use, amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line treatment. 1 This provides:

• 90-92% predicted clinical efficacy against major pathogens 1
• Coverage against β-lactamase-producing H. influenzae and M. catarrhalis 1
• Enhanced activity against drug-resistant S. pneumoniae 1

The clavulanate component specifically addresses the β-lactamase resistance problem that makes cephalexin ineffective. 1

Alternative Options for Penicillin Allergy

If the patient has documented penicillin allergy:

• Second-generation cephalosporins (cefuroxime-axetil) or third-generation cephalosporins (cefpodoxime, cefdinir) provide adequate coverage against both H. influenzae and S. pneumoniae 1
• These agents have negligible cross-reactivity risk with penicillin allergy 1
• Respiratory fluoroquinolones (levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily) for severe penicillin allergy 1

Confirming Bacterial Sinusitis First

Before prescribing antibiotics, verify the patient meets criteria for acute bacterial sinusitis (not viral rhinosinusitis): 2

• Persistent symptoms ≥10 days without improvement (nasal discharge, congestion, facial pain) 2
• Severe symptoms for ≥3-4 consecutive days (fever ≥39°C with purulent discharge) 2
• "Double sickening" pattern (initial improvement followed by worsening) 2

This patient's symptoms since last week (likely <10 days) may not yet meet bacterial criteria unless severe features are present. 2

Essential Adjunctive Therapies

Regardless of antibiotic choice, add: 1

• Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily) to reduce inflammation 1
• Saline nasal irrigation for symptomatic relief 1
• Analgesics (acetaminophen or ibuprofen) for pain and fever 1
• Adequate hydration and warm facial packs 1

Treatment Monitoring

• Reassess at 3-5 days: If no improvement, switch to high-dose amoxicillin-clavulanate or respiratory fluoroquinolone 1
• Reassess at 7 days: If symptoms persist, reconfirm diagnosis and consider complications 1
• Complete the full antibiotic course (typically 10-14 days or until symptom-free for 7 days) to prevent relapse 1

Critical Pitfall to Avoid

Never use first-generation cephalosporins (cephalexin, cefadroxil) for sinusitis treatment. 1 Despite the patient's previous prescription history, this represents suboptimal therapy that likely contributed to treatment failure or recurrence. The historical use of cephalexin for this indication (as shown in older 1985 research 3) predates current understanding of resistance patterns and guideline recommendations.