Antibiotic Treatment for Acute Bacterial Sinusitis
First-Line Treatment
Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-7 days is the preferred first-line antibiotic for adults with acute bacterial sinusitis. 1, 2
The combination formulation is superior to plain amoxicillin because 20-30% of Haemophilus influenzae and 12-28% of Moraxella catarrhalis produce β-lactamase, rendering plain amoxicillin ineffective 2. High-dose amoxicillin-clavulanate (2 g/125 mg twice daily) should be used for patients with recent antibiotic use within the past month, age >65 years, moderate-to-severe symptoms, or immunocompromised state 1, 2.
Confirm Bacterial Diagnosis Before Prescribing
Antibiotics should only be prescribed when one of three diagnostic criteria is met 1, 2:
- Persistent symptoms ≥10 days without improvement
- Severe symptoms (fever ≥39°C with purulent nasal discharge) for ≥3-4 consecutive days
- "Double sickening" - worsening after initial improvement from a viral upper respiratory infection
Most acute rhinosinusitis (98-99.5%) is viral and resolves spontaneously within 7-10 days without antibiotics 1, 2.
Treatment Duration
Adults: 5-7 days of treatment is sufficient for uncomplicated cases, with comparable efficacy to 10-day regimens and fewer adverse effects 1, 2, 3.
Children: 10-14 days of treatment is required 1, 4.
Penicillin-Allergic Patients
Non-Severe Allergy (Rash, Non-Type I Hypersensitivity)
Second- or third-generation cephalosporins are the preferred alternatives 1, 2:
- Cefuroxime-axetil (second-generation)
- Cefpodoxime-proxetil or cefdinir (third-generation)
The risk of serious cross-reactivity between penicillins and second/third-generation cephalosporins is negligible 2.
Severe Allergy (Anaphylaxis, Type I Hypersensitivity)
Respiratory fluoroquinolones are recommended 1, 2:
- Levofloxacin 500-750 mg once daily for 10-14 days 5
- Moxifloxacin 400 mg once daily for 10 days
Fluoroquinolones demonstrate 90-92% predicted clinical efficacy and 100% microbiologic eradication of S. pneumoniae, including multi-drug resistant strains 2.
Treatment Failure Protocol
Reassess patients at 3-5 days 1, 2. If no improvement or worsening symptoms occur:
- Switch to high-dose amoxicillin-clavulanate (if not already prescribed) 1, 2
- Switch to respiratory fluoroquinolone (levofloxacin or moxifloxacin) if amoxicillin-clavulanate fails 1, 2
- Consider imaging or specialist referral if no improvement after 7 days of appropriate second-line therapy 1, 2
Adjunctive Therapies
Intranasal corticosteroids should be added to antibiotic therapy in all patients to reduce mucosal inflammation and improve symptom resolution 1, 2. Options include mometasone, fluticasone, or budesonide twice daily 1.
Additional supportive measures include 1, 2:
- Intranasal saline irrigation
- Analgesics (acetaminophen or NSAIDs)
- Adequate hydration
Pediatric Dosing
Standard-dose amoxicillin: 45 mg/kg/day in 2 divided doses for children without risk factors 1, 4.
High-dose amoxicillin: 80-90 mg/kg/day in 2 divided doses for children with risk factors (age <2 years, daycare attendance, recent antibiotic use, or high local resistance rates) 6, 1, 4.
High-dose amoxicillin-clavulanate: 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses for treatment failures or children with risk factors 6, 1, 4.
Critical Pitfalls to Avoid
Do not use plain amoxicillin as first-line therapy given the high prevalence of β-lactamase-producing organisms 2.
Do not prescribe antibiotics for symptoms lasting <10 days unless severe symptoms are present (fever ≥39°C with purulent discharge for ≥3 consecutive days) 1, 2.
Do not use azithromycin or clarithromycin due to resistance rates exceeding 20-25% for both S. pneumoniae and H. influenzae 2, 4.
Do not continue ineffective antibiotics beyond 3-5 days - failure to reassess and switch therapy leads to prolonged illness and potential complications 1, 2.
Do not use fluoroquinolones as routine first-line therapy in patients without documented β-lactam allergies, as this promotes antimicrobial resistance 1, 2.
Watchful Waiting Option
For adults with uncomplicated acute bacterial sinusitis, watchful waiting without immediate antibiotics is an appropriate initial strategy when reliable follow-up can be assured 1, 2. Antibiotics should be started only if no improvement occurs by 7 days or symptoms worsen at any time 1, 2.