First-Line Antibiotic Treatment for Uncomplicated Acute Bacterial Sinusitis in Adults
Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5–10 days is the preferred first-line antibiotic for uncomplicated acute bacterial sinusitis in adults without drug allergies, providing 90–92% predicted clinical efficacy against the major pathogens. 1, 2
Confirming the Diagnosis Before Prescribing
Before initiating antibiotics, confirm that the patient meets at least one of three diagnostic criteria for acute bacterial rhinosinusitis (ABRS):
- Persistent symptoms ≥10 days without improvement: purulent nasal discharge plus nasal obstruction or facial pain/pressure/fullness 1, 2
- Severe symptoms ≥3–4 consecutive days: fever ≥39°C with purulent nasal discharge and facial pain 1, 2
- "Double sickening": initial improvement from a viral URI followed by worsening within 10 days 1, 2
Critical context: Approximately 98–99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7–10 days without antibiotics. 1, 2 Do not prescribe antibiotics for symptoms <10 days unless the severe criteria above are met. 1, 2
Standard First-Line Regimen
Dosing and Duration
- Standard dose: Amoxicillin-clavulanate 875 mg/125 mg orally twice daily 1, 2
- Duration: 5–10 days, or until symptom-free for 7 consecutive days (typically 10–14 days total) 1, 2
- Shorter courses (5–7 days) provide comparable efficacy with fewer adverse effects and are increasingly recommended 2
Rationale for Amoxicillin-Clavulanate Over Plain Amoxicillin
The clavulanate component is essential because 30–40% of Haemophilus influenzae and 90–100% of Moraxella catarrhalis produce β-lactamase, rendering plain amoxicillin ineffective. 2 Plain amoxicillin may be used only for mild disease in patients who have not received antibiotics in the preceding 4–6 weeks. 2
High-Dose Regimen for Risk Factors
Use high-dose amoxicillin-clavulanate 2 g/125 mg twice daily when any of the following risk factors are present:
- Recent antibiotic use (within past 4–6 weeks) 2
- Age >65 years 2
- Daycare attendance or close contact with daycare children 2
- Moderate-to-severe symptoms 2
- Comorbidities (diabetes, chronic cardiac/hepatic/renal disease) 2
- Immunocompromised state 2
- Smoking or exposure to secondhand smoke 2
This high-dose regimen enhances coverage against drug-resistant Streptococcus pneumoniae (DRSP). 2
Alternatives for Penicillin-Allergic Patients
Non-Severe (Non-Type I) Penicillin Allergy
For patients with mild reactions (e.g., rash without anaphylaxis):
- Second-generation cephalosporins: Cefuroxime-axetil 1, 2
- Third-generation cephalosporins: Cefpodoxime-proxetil, cefdinir, or cefprozil 1, 2
- Duration: 10 days 1, 2
- Cross-reactivity is negligible (<1%) with these agents 2, 3
Severe (Type I/Anaphylactic) Penicillin Allergy
For patients with documented anaphylaxis, urticaria, or angioedema:
- Levofloxacin 500 mg once daily for 10–14 days 1, 2
- Moxifloxacin 400 mg once daily for 10 days 1, 2
- Both provide 90–92% predicted efficacy against multidrug-resistant S. pneumoniae and β-lactamase-producing organisms 1, 2
Reserve fluoroquinolones for severe penicillin allergy or treatment failure to prevent resistance development. 1, 2
Suboptimal Alternative
- Doxycycline 100 mg once daily for 10 days is acceptable but inferior, with only 77–81% predicted efficacy and a 20–25% bacteriologic failure rate due to limited H. influenzae coverage 1, 2
- Use only when fluoroquinolones and cephalosporins are contraindicated 1, 2
- Contraindicated in children <8 years due to tooth enamel discoloration risk 2
Pediatric Dosing
Standard Therapy
High-Dose Therapy (Risk Factors Present)
- Amoxicillin 80–90 mg/kg/day divided twice daily for children with:
High-Dose Amoxicillin-Clavulanate
Duration and Reassessment
- Minimum 10–14 days (longer than adult courses) 1, 2
- Reassess at 72 hours: if no improvement or worsening, switch to high-dose amoxicillin-clavulanate 1, 2
Alternatives for Penicillin-Allergic Children
- Cefpodoxime proxetil 8 mg/kg/day divided twice daily 1
- Ceftriaxone 50 mg/kg IM/IV once daily for children unable to tolerate oral medication 1
Pregnant Patients
- Amoxicillin-clavulanate is safe in pregnancy and remains the first-line agent 2
- High-dose amoxicillin-clavulanate should be used if risk factors for resistant organisms are present 2
- Avoid fluoroquinolones (pregnancy category C; risk of cartilage damage in fetus) 2
- Avoid doxycycline (pregnancy category D; risk of tooth discoloration and bone growth inhibition) 2
- For severe penicillin allergy in pregnancy, cephalosporins (cefuroxime, cefpodoxime, cefdinir) are preferred 2
Watchful Waiting Option
For adults with uncomplicated ABRS and reliable follow-up, initial observation without antibiotics is appropriate:
- Initiate antibiotics only if no improvement by day 7 or if symptoms worsen at any time 1, 2, 4
- The number needed to treat (NNT) is 10–15 to achieve one additional cure compared with placebo 2
- This approach reduces unnecessary antibiotic exposure while maintaining safety 1, 2, 4
Essential Adjunctive Therapies (Add to All Patients)
Intranasal Corticosteroids (Strong Evidence)
- Mometasone, fluticasone, or budesonide twice daily significantly reduce mucosal inflammation and accelerate symptom resolution 1, 2
- Supported by strong evidence from multiple randomized controlled trials 1, 2
Saline Nasal Irrigation
Analgesics
Decongestants
- Oral or topical decongestants may be used; limit topical agents to ≤3 days to avoid rebound congestion 2
Monitoring and Reassessment
Early Reassessment (Days 3–5)
- If no clinical improvement (persistent purulent drainage, unchanged facial pain, or worsening), switch to:
Day 7 Reassessment
- Persistent or worsening symptoms warrant:
Expected Timeline of Recovery
- Noticeable improvement within 3–5 days of appropriate antibiotic therapy 2
- Complete resolution by 10–14 days or when symptom-free for 7 consecutive days 1, 2
- Only 30–41% of patients improve by days 3–5; zero improvement at this stage indicates likely treatment failure 2
Antibiotics to Avoid
Macrolides (Azithromycin, Clarithromycin)
- 20–25% resistance rates in S. pneumoniae and H. influenzae make them unsuitable 1, 2
- The American Academy of Pediatrics explicitly contraindicates azithromycin for acute bacterial sinusitis 2
Trimethoprim-Sulfamethoxazole
First-Generation Cephalosporins (Cephalexin)
- Inadequate coverage because ~50% of H. influenzae strains produce β-lactamase 2
Referral to Otolaryngology
Refer immediately if any of the following occur:
- No improvement after 7 days of appropriate second-line antibiotic therapy 1, 2
- Worsening symptoms at any point during treatment 1, 2
- Suspected complications: severe headache, visual changes, periorbital swelling/erythema, proptosis, diplopia, altered mental status, cranial nerve deficits 1, 2
- Recurrent sinusitis (≥3 episodes per year) requiring evaluation for underlying allergic rhinitis, immunodeficiency, or anatomic abnormalities 1, 2
Critical Pitfalls to Avoid
- Do not prescribe antibiotics for symptoms <10 days unless severe features (fever ≥39°C with purulent discharge for ≥3 consecutive days) are present 1, 2
- Do not obtain routine imaging (X-ray or CT) for uncomplicated ABRS; up to 87% of viral URIs show sinus abnormalities on imaging, leading to unnecessary interventions 2
- Ensure adequate treatment duration (≥5 days for adults, ≥10 days for children) to prevent relapse 1, 2
- Do not use fluoroquinolones as first-line therapy in patients without documented β-lactam allergy to prevent resistance development 1, 2
- Gastrointestinal adverse effects with amoxicillin-clavulanate are common: diarrhea in 40–43% of patients; severe diarrhea in 7–8% 2