What is the first line treatment for a adult patient presenting with symptoms of a sinus infection, with no severe allergies or contraindications?

First-Line Treatment for Sinus Infection

For adults with acute bacterial sinusitis, amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line antibiotic, though watchful waiting without immediate antibiotics is equally appropriate when reliable follow-up can be assured. 1, 2

Confirm the Diagnosis First

Before prescribing antibiotics, verify the patient meets criteria for acute bacterial rhinosinusitis (ABRS) rather than viral rhinosinusitis: 1

• Persistent symptoms ≥10 days without improvement (purulent nasal discharge, nasal obstruction, facial pain/pressure) 1
• Severe symptoms for ≥3-4 consecutive days (fever ≥39°C with purulent discharge) 1, 3
• "Double sickening" - worsening after initial improvement from viral URI 1

Critical pitfall: 98-99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7-10 days without antibiotics. 4, 5 Do not prescribe antibiotics for symptoms <10 days unless severe features are present. 1, 2

First-Line Antibiotic Selection

Amoxicillin-clavulanate 875 mg/125 mg twice daily is preferred over plain amoxicillin due to increasing prevalence of β-lactamase-producing organisms (Haemophilus influenzae and Moraxella catarrhalis). 4, 6, 2 This provides 90-92% predicted clinical efficacy against the major pathogens (Streptococcus pneumoniae, H. influenzae, M. catarrhalis). 7, 8

Plain amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease) remains acceptable for uncomplicated cases without recent antibiotic exposure within the past 4-6 weeks. 4, 6, 2

Use high-dose amoxicillin-clavulanate (2 g amoxicillin/125 mg clavulanate twice daily) for patients with: 4, 6, 2

• Recent antibiotic use within past month
• Age >65 years
• Moderate-to-severe symptoms
• Comorbid conditions or immunocompromised state

Treatment Duration

Standard duration is 5-10 days, with most guidelines recommending treatment until symptom-free for 7 days (typically 10-14 days total). 4, 6, 2 Recent evidence supports shorter 5-7 day courses with comparable efficacy and fewer adverse effects. 4, 2

Watchful Waiting as Alternative

Watchful waiting without immediate antibiotics is an equally appropriate initial strategy for uncomplicated ABRS when reliable follow-up can be assured. 1, 2 Start antibiotics only if no improvement by 7 days or symptoms worsen at any time. 1

The number needed to treat with antibiotics is 10-15 to get one additional person better after 7-15 days, as most patients improve naturally. 1

For Penicillin-Allergic Patients

For non-severe (non-Type I) penicillin allergy: 4, 2

• Second-generation cephalosporins: cefuroxime-axetil
• Third-generation cephalosporins: cefpodoxime-proxetil, cefdinir, or cefprozil

The risk of cross-reactivity with second- and third-generation cephalosporins in penicillin-allergic patients is negligible. 4

For severe Type I penicillin allergy (anaphylaxis): 4, 2

• Respiratory fluoroquinolones: levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily for 10 days

Do NOT use: 4

• Azithromycin or other macrolides (20-25% resistance rates)
• Trimethoprim-sulfamethoxazole (50% resistance for S. pneumoniae)
• First-generation cephalosporins like cephalexin (inadequate H. influenzae coverage)

Essential Adjunctive Therapies

All patients should receive symptomatic treatment regardless of antibiotic decision: 1, 2

• Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily) - reduce mucosal inflammation and improve symptom resolution 1, 4, 2
• Saline nasal irrigation - provides symptomatic relief and removes mucus 1, 2
• Analgesics (acetaminophen or ibuprofen) - relieve pain and fever 1, 2
• Decongestants (systemic or topical) - but limit topical use to ≤3 days to avoid rhinitis medicamentosa 1, 6

When to Reassess and Switch Therapy

Reassess at 3-5 days: 4, 2

• If no improvement or worsening, switch to high-dose amoxicillin-clavulanate or respiratory fluoroquinolone
• Confirm diagnosis meets bacterial criteria

Reassess at 7 days: 1, 4

• If symptoms persist or worsen, reconfirm diagnosis and exclude complications
• Switch to second-line therapy (respiratory fluoroquinolones or high-dose amoxicillin-clavulanate)

Most patients should experience noticeable improvement within 3-5 days of appropriate antibiotic therapy, with 86-91% achieving cure or improvement by 7-15 days. 4

Avoid Imaging

Do not obtain radiographic imaging (X-ray or CT) for patients meeting diagnostic criteria for acute rhinosinusitis unless a complication (orbital cellulitis, meningitis, brain abscess) or alternative diagnosis is suspected. 1, 5