Amoxicillin-Clavulanate vs Amoxicillin for Sinusitis

Amoxicillin-clavulanate was not linked to lower treatment failure but was associated with a slightly higher risk of secondary infections compared with amoxicillin in adults with uncomplicated acute sinusitis.

By
Kathryn Wighton
April 20, 2026
3 min

Conexiant

At a Glance

Category	Detail
Condition	Uncomplicated acute sinusitis in adults
Key Mechanisms	Antibiotic treatment targeting bacterial sinus infections; amoxicillin-clavulanate includes beta-lactamase inhibitor
Target Population	Commercially insured adults aged 18 to 64 years with outpatient uncomplicated acute sinusitis
Care Setting	Outpatient clinical settings

Key Highlights

Treatment failure rates were similar (~3%) between standard-dose amoxicillin-clavulanate and amoxicillin.
Secondary infections, including yeast and Clostridioides difficile, were more frequent with amoxicillin-clavulanate.
No meaningful differences in treatment outcomes across age groups, sex, immune status, or dosing strategies.

Guideline-Based Recommendations

Diagnosis

Diagnosis based on clinical presentation of uncomplicated acute sinusitis in outpatient adults.

Management

Standard-dose amoxicillin is preferred first-line antibiotic treatment when antibiotics are indicated.
Reserve amoxicillin-clavulanate for specific cases due to higher risk of secondary infections.

Monitoring & Follow-up

Monitor for treatment failure defined as new antibiotic dispensation, outpatient or emergency visits, or hospitalization within 1 to 14 days.
Observe for antibiotic-associated adverse events, especially gastrointestinal symptoms and secondary infections.

Risks

Higher risk of secondary infections including yeast infections and rare Clostridioides difficile infections with amoxicillin-clavulanate.
Similar rates (~1%) of antibiotic-associated adverse events between both treatments.

Patient & Prescribing Data

Adults aged 18 to 64 years with uncomplicated acute sinusitis, commercially insured.

Amoxicillin and amoxicillin-clavulanate have comparable treatment failure rates; amoxicillin-clavulanate carries a slightly increased risk of secondary infections.

Clinical Best Practices

Prefer standard-dose amoxicillin as first-line therapy for uncomplicated acute sinusitis in adults without recent antibiotic exposure.
Consider patient age and clinical context but recognize minimal differences in outcomes across subgroups.
Be vigilant for secondary infections when prescribing amoxicillin-clavulanate.
Use propensity score matching and large datasets to inform antibiotic choice in outpatient sinusitis.