What is the first line treatment for an adult patient with bacterial sinusitis, without underlying health conditions or allergies?

First-Line Treatment for Bacterial Sinusitis in Adults

Amoxicillin with or without clavulanate is the first-line antibiotic for acute bacterial rhinosinusitis (ABRS) in adults, prescribed for 5 to 10 days when antibiotic therapy is chosen. 1

Initial Management Decision: Watchful Waiting vs. Antibiotics

Before prescribing antibiotics, clinicians must decide whether immediate antibiotic therapy is necessary:

• Watchful waiting (without antibiotics) is an appropriate initial strategy for uncomplicated ABRS when follow-up can be assured, as many patients improve spontaneously. 1
• Antibiotics should be started if the patient fails to improve by 7 days after diagnosis or worsens at any time. 1
• Immediate antibiotic therapy is indicated for patients with severe symptoms (high fever ≥38.3°C/101°F, severe pain, or moderate-to-severe illness). 1

Confirming the Diagnosis of Bacterial Sinusitis

Distinguish ABRS from viral upper respiratory infections before initiating antibiotics: 1

• Symptoms present for ≥10 days without improvement, OR 1, 2
• "Double worsening": symptoms worsen within 10 days after initial improvement, OR 1, 2
• Severe onset: high fever (≥39°C/102°F) with purulent nasal discharge for ≥3-4 consecutive days 3, 2

Key clinical features supporting bacterial etiology include: 1, 2

• Maxillary pain or facial tenderness (especially unilateral) 1, 2
• Purulent nasal secretions 1, 2
• Symptoms lasting ≥7 days 1, 2

First-Line Antibiotic Selection

Standard First-Line: Amoxicillin

Amoxicillin is recommended as first-line therapy for most adults with ABRS due to its safety, efficacy, low cost, and narrow microbiologic spectrum. 1

• Dosing: Standard-dose amoxicillin (500 mg three times daily) 4
• Duration: 5 to 10 days (shorter courses have fewer side effects with comparable efficacy) 1

When to Use Amoxicillin-Clavulanate Instead

Prescribe amoxicillin-clavulanate (instead of amoxicillin alone) for patients at high risk of antibiotic-resistant organisms: 1

Risk factors for resistance include: 1

• Antibiotic use within the past month 1
• Age >65 years 1
• Recent hospitalization 1
• Daycare contact 1
• Immunocompromised state 1
• Diabetes or chronic cardiac/hepatic/renal disease 1
• Moderate-to-severe infection or protracted symptoms 1
• Frontal or sphenoidal sinusitis 1
• History of recurrent ABRS 1
• Smoker or household smoker 1
• High community prevalence of resistant bacteria 1

High-dose amoxicillin-clavulanate (2 g orally twice daily or 90 mg/kg/day divided twice daily) is recommended for adults at high risk of penicillin-nonsusceptible Streptococcus pneumoniae infection. 1

Penicillin-Allergic Patients

For patients with penicillin allergy, prescribe either: 1

• Doxycycline, OR 1
• Respiratory fluoroquinolone (levofloxacin or moxifloxacin) 1

Avoid macrolides (azithromycin, clarithromycin) as first-line therapy due to resistance rates exceeding 20-25% among respiratory pathogens. 4

Reassessment and Treatment Failure

Reassess patients at 7 days if they worsen or fail to improve with initial management: 1

• Confirm the diagnosis of ABRS 1
• Exclude other causes of illness and detect complications 1
• If initially managed with observation, start antibiotic therapy 1
• If initially treated with amoxicillin, switch to amoxicillin-clavulanate 1

Adjunctive Symptomatic Therapy

Analgesics should be recommended based on pain severity to improve quality of life during treatment. 1

Intranasal corticosteroids are recommended as adjunctive therapy, particularly in patients with allergic rhinitis. 1

Topical decongestants may provide short-term relief but should not be used for more than 3-5 consecutive days due to risk of rebound congestion. 1

Antihistamines have no role in non-allergic patients and may worsen congestion by drying nasal mucosa. 1

Critical Pitfalls to Avoid

• Do not obtain sinus radiography or CT for uncomplicated ABRS, as imaging does not improve diagnostic accuracy and shows abnormalities in viral rhinosinusitis. 1, 5
• Do not prescribe broad-spectrum antibiotics (fluoroquinolones, third-generation cephalosporins) as first-line therapy unless specific risk factors for resistance are present. 1
• Do not continue the same antibiotic beyond 7 days without clinical improvement—this indicates treatment failure requiring reassessment and antibiotic change. 1
• Do not confuse tetracycline allergy with penicillin allergy, as these are separate drug classes with no cross-reactivity. 4