Augmentin Dosing for Acute Bacterial Sinusitis in Adults
For an otherwise healthy adult with acute bacterial sinusitis, prescribe Augmentin (amoxicillin-clavulanate) 875 mg/125 mg twice daily for 5-7 days.
Dosage Selection
The standard adult dose is 875 mg amoxicillin with 125 mg clavulanate twice daily 1. This formulation provides adequate coverage for the three main pathogens: Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.
High-dose Augmentin (2000 mg amoxicillin/125 mg clavulanate twice daily) should be reserved for specific high-risk situations 1:
- Recent antibiotic use within the past month
- Severe infection (fever ≥39°C/102°F, systemic toxicity)
- Age >65 years
- Geographic areas with >10% penicillin-nonsusceptible S. pneumoniae
- Immunocompromised status
- Recent hospitalization
Recent high-quality evidence from 2026 and 2021 found no benefit from high-dose over standard-dose Augmentin in adults with clinically diagnosed acute sinusitis 2, 3. The high-dose formulation increased severe diarrhea rates (7.7% vs 7.0% for standard dose) without improving outcomes 2.
Duration of Treatment
Treat for 5-7 days in uncomplicated cases. Guidelines traditionally recommended 10-14 days 4, but more recent evidence supports shorter courses. A 2000 study found that 5-day treatment with amoxicillin-clavulanate achieved 80% success rates, though 10-day treatment reached 85% 5. The difference was not statistically significant in patients without risk factors (recurrent sinusitis, previous sinus surgery).
The 2015 AAO-HNS guideline notes that adverse events are reduced with shorter duration therapy 1, making 5-7 days a reasonable approach for straightforward cases.
Important Clinical Considerations
When to Use Augmentin vs Plain Amoxicillin
Augmentin is NOT necessary for most patients. The most recent 2026 observational study of 521,244 adults found no difference in treatment failure between standard-dose amoxicillin-clavulanate and amoxicillin alone (3.0% vs 3.1%), but Augmentin caused more yeast infections (1.1% vs 0.8%) and C. difficile infections (0.04% vs 0.02%) 6. This was confirmed in a 2021 Veterans Affairs study of 89,627 patients showing equivalent efficacy but fewer gastrointestinal adverse events with amoxicillin alone 7.
Start with plain amoxicillin unless β-lactamase-producing organisms are suspected 4. Reserve Augmentin for:
- Failure to improve after 3-5 days on amoxicillin
- Moderate-to-severe infection at presentation
- Recent antibiotic exposure
- High local resistance rates
Monitoring and Follow-Up
Reassess at 3-5 days 4. If symptoms are improving, continue treatment until the patient is well for 7 days (typically 10-14 days total in older guidelines, though 5-7 days appears adequate based on newer data). If no improvement after 3-5 days, this represents treatment failure requiring antibiotic change.
Instruct patients to call immediately if symptoms worsen, particularly with:
- High fever
- Severe headache
- Visual changes
- Facial swelling or erythema
These may indicate complications requiring urgent evaluation 4.
Common Pitfalls
Overprescribing Augmentin: The clavulanate component increases adverse effects without benefit in most cases. Plain amoxicillin is equally effective and better tolerated 6, 7.
Excessive duration: Traditional 10-14 day courses may be unnecessary. Consider 5-7 days for uncomplicated cases 5.
Using high-dose unnecessarily: High-dose formulations (2000 mg twice daily) do not improve outcomes in typical acute sinusitis but increase diarrhea rates 2, 3.
Ignoring risk factors: Patients with recurrent sinusitis or previous sinus surgery may need longer treatment courses and closer monitoring 5.
Penicillin Allergy
For true penicillin allergy, alternatives include doxycycline or respiratory fluoroquinolones (levofloxacin, moxifloxacin) 1. Avoid macrolides and trimethoprim-sulfamethoxazole due to high resistance rates (>40% for macrolides, 50% for TMP-SMX against S. pneumoniae) 1.