What is the first‑line oral antibiotic and treatment duration for a healthy 44‑year‑old man with uncomplicated acute bacterial sinusitis?

Antibiotic Choice and Duration for Acute Bacterial Sinusitis in a 44-Year-Old Male

First-Line Antibiotic Selection

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5–10 days is the preferred first-line antibiotic for this patient, providing 90–92% predicted clinical efficacy against the three major sinusitis pathogens. 1

• The clavulanate component is essential because 30–40% of Haemophilus influenzae and 90–100% of Moraxella catarrhalis produce β-lactamase, rendering plain amoxicillin ineffective against these organisms. 1
• Plain amoxicillin 500 mg twice daily may be considered only if the patient has not received antibiotics in the preceding 4–6 weeks and has mild disease; otherwise, amoxicillin-clavulanate is strongly preferred. 1

Treatment Duration

A 5–7 day course of amoxicillin-clavulanate achieves comparable clinical cure rates to traditional 10-day regimens with fewer adverse effects. 1

• Continue therapy for 5–10 days or until the patient is symptom-free for 7 consecutive days (typically resulting in a 10–14 day total course). 1
• Recent high-quality evidence supports shorter 5–7 day courses as equally effective, with clinical cure rates of 74–80% comparable to 10-day regimens. 1, 2, 3
• Extending therapy beyond 7 days provides no additional clinical benefit and increases gastrointestinal side effects (diarrhea in 40–43% of patients; severe diarrhea in 7–8%). 1

Confirming the Diagnosis Before Prescribing

Antibiotics should be prescribed only when acute bacterial rhinosinusitis is confirmed by at least one of the following clinical patterns:

• Persistent symptoms ≥10 days without improvement (purulent nasal discharge plus obstruction or facial pain/pressure/fullness). 1
• Severe symptoms ≥3–4 consecutive days with fever ≥39°C, purulent discharge, and facial pain. 1
• "Double sickening" – initial improvement from a viral URI followed by worsening symptoms within 10 days. 1

Do not prescribe antibiotics for symptoms lasting <10 days unless severe features are present, because 98–99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7–10 days. 1

Watchful Waiting as an Alternative

Initial observation without antibiotics is appropriate for uncomplicated cases when reliable follow-up can be ensured. 1

• Start antibiotics only if there is no improvement by day 7 or if symptoms worsen at any time. 1
• The number needed to treat (NNT) with antibiotics is 10–15 to achieve one additional cure, reflecting the high rate of spontaneous recovery. 1

Essential Adjunctive Therapies (Add to All Patients)

Intranasal corticosteroids (mometasone, fluticasone, or budesonide) twice daily significantly reduce mucosal inflammation and accelerate symptom resolution; this recommendation is supported by strong evidence from multiple randomized controlled trials. 1, 4

• Saline nasal irrigation 2–3 times daily provides symptomatic relief and aids mucus clearance. 1
• Analgesics (acetaminophen or ibuprofen) for pain and fever control. 1
• Decongestants (oral or topical) may be used; limit topical agents to ≤3 days to avoid rebound congestion. 1

Monitoring and Reassessment Protocol

Reassess at 3–5 days: If no clinical improvement (persistent purulent drainage, unchanged facial pain, or worsening), switch immediately to high-dose amoxicillin-clavulanate (2 g/125 mg twice daily) or a respiratory fluoroquinolone (levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily). 1

Reassess at 7 days: Persistent or worsening symptoms warrant confirmation of diagnosis, exclusion of complications (orbital cellulitis, meningitis, intracranial abscess), and consideration of imaging or ENT referral. 1

• Only 30–41% of patients show improvement by days 3–5; zero improvement at this point indicates treatment failure. 1
• By day 7, approximately 73–85% of patients show clinical improvement even with placebo. 1

Alternatives for Penicillin Allergy

Non-severe (non-type I) penicillin allergy: Use a second- or third-generation cephalosporin (cefuroxime-axetil, cefpodoxime-proxetil, cefdinir, or cefprozil) for 10 days; cross-reactivity is negligible. 1, 4

Severe (type I/anaphylactic) penicillin allergy: Use a respiratory fluoroquinolone—levofloxacin 500 mg once daily for 10–14 days or moxifloxacin 400 mg once daily for 10 days—with 90–92% predicted efficacy against multidrug-resistant Streptococcus pneumoniae. 1, 4

Doxycycline 100 mg once daily for 10 days is an acceptable but suboptimal alternative (predicted efficacy 77–81% with a 20–25% bacteriologic failure rate due to limited H. influenzae coverage). 1, 4

Antibiotics to Avoid

Macrolides (azithromycin, clarithromycin) should not be used due to 20–25% resistance rates for both S. pneumoniae and H. influenzae. 1, 4

Trimethoprim-sulfamethoxazole has 50% resistance in S. pneumoniae and 27% in H. influenzae. 1, 4

First-generation cephalosporins (cephalexin) provide inadequate coverage because ~50% of H. influenzae strains produce β-lactamase. 1, 4

Critical Pitfalls to Avoid

• Do not obtain routine imaging (X-ray or CT) for uncomplicated acute bacterial rhinosinusitis; up to 87% of viral URIs show sinus abnormalities on imaging, leading to unnecessary interventions. 1
• Ensure a minimum treatment duration of 5 days for adults to prevent relapse. 1
• Do not wait beyond 3–5 days to change therapy in non-responders; early identification prevents complications. 1
• Reserve fluoroquinolones for second-line therapy or documented severe β-lactam allergy to prevent resistance development. 1, 4

Referral to Otolaryngology

Refer immediately if any of the following occur:

• No improvement after 7 days of appropriate second-line antibiotic therapy. 1
• Worsening symptoms at any point (increasing facial pain, fever, purulent drainage). 1
• Suspected complications (severe headache, visual changes, periorbital swelling/erythema, proptosis, diplopia, altered mental status, cranial nerve deficits). 1
• Recurrent sinusitis (≥3 episodes per year) requiring evaluation for underlying allergic rhinitis, immunodeficiency, or anatomic abnormalities. 1, 4