In an otherwise healthy adult with two weeks of sinus pressure, cough, nasal drainage, bilateral ear congestion, chills, and headache, what is the most likely diagnosis and appropriate first‑line treatment?

Acute Bacterial Rhinosinusitis (ABRS)

This is acute bacterial rhinosinusitis requiring antibiotic therapy with amoxicillin 500 mg three times daily for 7-10 days, based on the 2-week duration of purulent symptoms meeting diagnostic criteria for bacterial superinfection. 1, 2

Diagnostic Reasoning

Your symptom constellation—sinus pressure, purulent nasal drainage, bilateral ear congestion, headache, cough, and chills persisting for 2 weeks—meets established criteria for ABRS rather than simple viral rhinosinusitis. 1

Key diagnostic criteria met:

• Duration >10 days without improvement is the primary indicator distinguishing bacterial from viral infection, as viral URIs typically resolve within 7-10 days and fewer than 2% progress to bacterial superinfection 1
• Purulent nasal drainage combined with facial pressure/pain are the two symptoms with highest correlation to bacterial disease 1, 2
• Bilateral ear congestion reflects mucosal continuity of the upper respiratory tract, where sinus inflammation extends to the middle ear 2
• Chills and headache suggest systemic inflammatory response to bacterial infection 1

The 2-week timeframe is critical: sinus aspiration studies demonstrate significant bacterial growth in approximately 60% of patients with URI symptoms lasting ≥10 days, compared to predominantly viral pathogens in shorter durations. 1

First-Line Antibiotic Treatment

Amoxicillin 500 mg orally three times daily for 7-10 days is the evidence-based first-line therapy. 2, 3

This targets the three most common bacterial pathogens:

• Streptococcus pneumoniae 1, 4, 5
• Haemophilus influenzae 1, 4, 5
• Moraxella catarrhalis 1, 4, 5

When to use amoxicillin-clavulanate instead:

• Recent antibiotic use within 4-6 weeks 3, 4
• Recent hospitalization 3
• Immunocompromised state 3
• Geographic areas with high beta-lactamase-producing bacterial resistance (>30%) 4, 5

If you have any of these risk factors, start with amoxicillin-clavulanate (high-dose: 2000 mg/125 mg twice daily or 875 mg/125 mg twice daily) instead. 4

Symptomatic Adjunctive Therapy

Combine antibiotics with the following for symptom relief:

• Intranasal saline irrigation 2-3 times daily—no rebound effect and mechanically clears purulent secretions 6, 3
• Intranasal corticosteroid spray (e.g., fluticasone, mometasone) twice daily to reduce mucosal inflammation and promote sinus drainage 2, 3, 7
• Oral decongestant (pseudoephedrine 120 mg twice daily) for nasal congestion 6
• Analgesics (ibuprofen 400-600 mg every 6-8 hours or acetaminophen) for headache and facial pain 1, 6

Avoid topical decongestants (oxymetazoline) beyond 3-5 days due to rebound congestion risk. 6

Follow-Up and Red Flags

Reassess in 3-5 days to confirm clinical improvement (reduced purulent discharge, decreased facial pressure, improved energy). 2

Switch to amoxicillin-clavulanate if no improvement after 3-5 days of amoxicillin monotherapy, as this suggests beta-lactamase-producing organisms. 2, 3

Return immediately for:

• Periorbital edema, erythema, or vision changes—suggests orbital complications requiring urgent evaluation 6, 3
• Severe unilateral facial pain with high fever (>39°C)—may indicate complicated sinusitis 6, 3
• Severe headache with neck stiffness or mental status changes—raises concern for intracranial extension 6
• Worsening after initial improvement—"double sickening" pattern suggesting resistant organism or complication 3

Common Pitfalls to Avoid

Do not withhold antibiotics in favor of "watchful waiting" when symptoms have persisted 2 weeks—this duration definitively exceeds the viral URI timeline and meets bacterial infection criteria. 1, 3

Do not obtain imaging (CT or X-ray) for straightforward ABRS meeting clinical criteria, as radiographic findings have only 61% specificity and do not distinguish viral from bacterial causes. 1, 3

Do not assume this is allergic rhinitis—the evolution from initial URI to persistent purulent discharge, absence of itching/sneezing, and lack of seasonal pattern argue against allergy. 2, 6

Do not use newer-generation antihistamines (loratadine, cetirizine) for symptom relief, as they lack anticholinergic activity and are ineffective for post-viral upper airway symptoms; use first-generation antihistamines (e.g., dexbrompheniramine) if antihistamine therapy is desired. 6