What are the recommended antibiotics for treating acute bacterial sinusitis?

Recommended Antibiotics for Acute Bacterial Sinusitis

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-7 days is the preferred first-line antibiotic for adults with acute bacterial sinusitis, due to the increasing prevalence of β-lactamase-producing organisms that render plain amoxicillin ineffective. 1, 2, 3

First-Line Treatment Selection

Adults

• Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-7 days is the preferred first-line choice 1, 2, 3
• The clavulanate component provides essential coverage against β-lactamase-producing Haemophilus influenzae (20-30% of cases) and Moraxella catarrhalis (12-28% of cases) 2, 4
• Plain amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease) remains acceptable only for uncomplicated cases without recent antibiotic exposure 1, 3
• Treatment duration is 5-10 days, with most guidelines recommending treatment until symptom-free for 7 days 1, 3

Pediatric Patients

• Standard therapy: Amoxicillin 45 mg/kg/day in 2 divided doses for children without recent antibiotic use 1, 3
• High-dose therapy: Amoxicillin-clavulanate 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses for high-risk children 1, 3
• High-risk criteria include: age <2 years, daycare attendance, antibiotic use within past 4-6 weeks, or high local resistance rates 1
• Treatment duration is 10-14 days for children 1, 3

Penicillin-Allergic Patients

Non-Severe Allergy (Rash, Delayed Reactions)

• Second-generation cephalosporins: Cefuroxime-axetil 1, 2, 3
• Third-generation cephalosporins: Cefpodoxime-proxetil or cefdinir (preferred for superior H. influenzae coverage) 1, 2, 3
• The risk of serious cross-reactivity between penicillins and second/third-generation cephalosporins is negligible 1, 3
• Cefdinir is often preferred based on patient acceptance 5

Severe Type I Hypersensitivity (Anaphylaxis)

• Respiratory fluoroquinolones: Levofloxacin 500 mg once daily for 10-14 days 1, 2, 3
• Alternative: Moxifloxacin 400 mg once daily for 10 days 1, 2
• Fluoroquinolones provide 90-92% predicted clinical efficacy against both drug-resistant S. pneumoniae and β-lactamase-producing organisms 1, 6

Second-Line Treatment for Treatment Failure

If no improvement occurs within 72 hours (pediatrics) or 3-5 days (adults), switch to a respiratory fluoroquinolone. 1, 2, 3

• Levofloxacin 500-750 mg once daily for 10-14 days 1, 2, 6
• Alternative: Moxifloxacin 400 mg once daily for 10 days 1, 2
• Fluoroquinolones demonstrate 100% microbiologic eradication of S. pneumoniae, including multi-drug resistant strains (MDRSP) 1, 6
• For pediatric patients failing initial therapy, switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component) 1

Antibiotics to AVOID

Never Use as First-Line

• Azithromycin and other macrolides have resistance rates exceeding 20-25% for both S. pneumoniae and H. influenzae 1, 2, 3
• Trimethoprim-sulfamethoxazole has resistance rates of 50% for S. pneumoniae and 27% for H. influenzae 1
• Clindamycin monotherapy lacks activity against H. influenzae and M. catarrhalis, leading to 30-40% failure rates 1

Reserve Fluoroquinolones Appropriately

• Do not use fluoroquinolones as routine first-line therapy 1, 2, 3
• Reserve for: treatment failures, complicated sinusitis (frontal/ethmoidal/sphenoidal), multi-drug resistant S. pneumoniae, or severe beta-lactam allergy 1, 2, 3

Special Considerations by Anatomic Location

Maxillary Sinusitis (Most Common)

• Use standard first-line antibiotics: amoxicillin-clavulanate 1
• Symptoms include unilateral/bilateral infraorbital pain worsening when bending forward, pulsatile, peaking evening/night 1

Frontal, Ethmoidal, or Sphenoidal Sinusitis

• Reserve fluoroquinolones (levofloxacin or moxifloxacin) due to potential for serious complications 1
• These locations carry higher risk of intracranial complications 1

Adjunctive Therapies

Add intranasal corticosteroids to antibiotic therapy in all patients with acute bacterial sinusitis. 1, 2, 3

• Intranasal corticosteroids (mometasone, fluticasone, budesonide) twice daily reduce mucosal inflammation and improve symptom resolution 1, 3
• Short-term oral corticosteroids may be reasonable for patients with marked mucosal edema or who fail initial treatment 1
• Additional supportive measures: intranasal saline irrigation, adequate hydration, analgesics (acetaminophen, NSAIDs), warm facial packs 1, 3

Critical Pitfalls to Avoid

• Do not prescribe antibiotics for viral rhinosinusitis—ensure patients meet diagnostic criteria: symptoms >10 days without improvement, severe symptoms (fever ≥39°C with purulent discharge) for 3-4 consecutive days, or "double sickening" (worsening after initial improvement) 1, 2, 3
• Do not use plain amoxicillin as first-line therapy given high prevalence (20-30%) of β-lactamase-producing organisms 2
• Do not continue ineffective antibiotics beyond 3-5 days—failure to reassess and switch therapy leads to prolonged illness and potential complications 1, 2, 3
• Reassess patients at 72 hours (pediatrics) or 3-5 days (adults)—if no improvement, switch antibiotics or re-evaluate diagnosis 1, 3
• Complete the full course of antibiotics even after symptoms improve to prevent relapse 1
• Do not use systemic corticosteroids without antibiotics when bacterial sinusitis is suspected, as this may suppress immune response and allow bacterial proliferation 1

When to Escalate or Refer

• No improvement after 7 days of appropriate second-line therapy 1
• Worsening symptoms at any time during treatment 1
• Suspected complications: orbital cellulitis, meningitis, intracranial abscess 1
• Recurrent sinusitis (≥3 episodes per year)—evaluate for underlying allergic rhinitis, immunodeficiency, or anatomical abnormalities 1
• Symptoms refractory to two courses of appropriate antibiotics 1