What are the first line antibiotics for acute bacterial sinusitis in adults and pediatric patients?

First-Line Antibiotics for Acute Bacterial Sinusitis

Adults

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line antibiotic for acute bacterial sinusitis in adults. 1, 2

Standard First-Line Treatment

• Amoxicillin-clavulanate is superior to plain amoxicillin because 10-42% of Haemophilus influenzae and nearly 100% of Moraxella catarrhalis produce β-lactamase, rendering plain amoxicillin ineffective against these organisms 2
• The standard dose is 875 mg/125 mg twice daily for 5-10 days 1, 2
• Recent evidence supports shorter 5-7 day courses with comparable efficacy and fewer adverse effects compared to traditional 10-day regimens 1

High-Dose Regimen for High-Risk Patients

Use high-dose amoxicillin-clavulanate (2 g amoxicillin/125 mg clavulanate twice daily) for patients with: 1

• Recent antibiotic use within the past 4-6 weeks 1
• Age >65 years 1
• Moderate-to-severe symptoms 1
• Comorbid conditions or immunocompromised state 1

Alternative First-Line Options for Penicillin Allergy

For non-Type I (non-anaphylactic) penicillin allergy, second- or third-generation cephalosporins are preferred: 1, 2

• Cefuroxime-axetil (second-generation cephalosporin) 1
• Cefpodoxime-proxetil (third-generation cephalosporin with superior activity against H. influenzae) 1
• Cefdinir (third-generation cephalosporin) 1, 2

The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible 1

For Severe Penicillin Allergy (Type I/Anaphylaxis)

Respiratory fluoroquinolones are reserved for patients with documented severe β-lactam allergies: 1

• Levofloxacin 500 mg once daily for 10-14 days 1
• Moxifloxacin 400 mg once daily for 10 days 1, 3
• These achieve 90-92% predicted clinical efficacy against drug-resistant S. pneumoniae and β-lactamase-producing organisms 1

What NOT to Use as First-Line

Azithromycin and other macrolides should NOT be used due to resistance rates of 20-25% for both S. pneumoniae and H. influenzae 1, 2

Trimethoprim-sulfamethoxazole should NOT be used due to 50% resistance in S. pneumoniae and 27% resistance in H. influenzae 1

Doxycycline is suboptimal with only 77-81% predicted clinical efficacy compared to 90-92% for first-line agents, and should be reserved for penicillin-allergic patients when cephalosporins are contraindicated 1

---

Pediatric Patients (Ages 1-18 Years)

Amoxicillin 45 mg/kg/day divided twice daily for 10-14 days is the first-line treatment for uncomplicated acute bacterial sinusitis in children. 4, 5

Standard-Dose Amoxicillin

Use standard-dose amoxicillin (45 mg/kg/day in 2 divided doses) for children with: 4, 5

• No antibiotic exposure in the past 4-6 weeks 5
• Not attending daycare 5
• Age >2 years 5

High-Dose Amoxicillin or Amoxicillin-Clavulanate

Use high-dose amoxicillin (80-90 mg/kg/day in 2 divided doses) OR high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses) for children with: 4, 5

• Age <2 years 4, 5
• Daycare attendance 4, 5
• Recent antibiotic use within the past 4-6 weeks 4, 5
• High local prevalence of resistant S. pneumoniae 4, 5

The clavulanate component provides coverage against β-lactamase-producing H. influenzae and M. catarrhalis, which have become increasingly prevalent 1

Alternative Options for Penicillin-Allergic Children

For non-Type I penicillin allergy: 1, 5

• Cefpodoxime proxetil 8 mg/kg/day in two doses 1
• Cefdinir 1, 5
• Cefuroxime 1, 5

For Children Unable to Tolerate Oral Medications

Ceftriaxone 50 mg/kg IM/IV as a single dose can be used for children who are vomiting or cannot take oral medications 1, 5

Treatment Duration

Children require 10-14 days of antibiotic treatment, which is longer than the 5-7 days now recommended for adults 4, 1, 5

---

Confirming Bacterial Sinusitis Before Prescribing

Antibiotics should only be prescribed when acute bacterial sinusitis is confirmed by one of three clinical patterns: 1, 2

1. Persistent symptoms ≥10 days without clinical improvement (nasal discharge, daytime cough, or both) 4, 1
2. Severe symptoms for ≥3-4 consecutive days (fever ≥39°C/102.2°F with purulent nasal discharge) 4, 1
3. "Double sickening" (worsening of respiratory symptoms after initial improvement from a viral URI) 4, 1

Most acute rhinosinusitis (98-99.5%) is viral and resolves spontaneously within 7-10 days without antibiotics 1

---

Reassessment and Treatment Failure Protocol

Adults

Reassess at 3-5 days: If no improvement, switch to high-dose amoxicillin-clavulanate or a respiratory fluoroquinolone 1

Reassess at 7 days: If symptoms persist or worsen, reconfirm diagnosis and switch to second-line therapy 1

Pediatric Patients

Reassess at 72 hours: If worsening symptoms or failure to improve, switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate) 4, 5

Only 9% of placebo-treated children improve between days 3-10 after failing at day 3, making the 72-hour reassessment critical 5

---

Essential Adjunctive Therapies

Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily) should be added to antibiotic therapy in all patients to reduce mucosal inflammation and improve symptom resolution 1

Saline nasal irrigation provides symptomatic relief and removes mucus 1

Analgesics (acetaminophen or ibuprofen) for pain and fever management 1

---

Critical Pitfalls to Avoid

Do not prescribe antibiotics for symptoms lasting <10 days unless severe symptoms are present (fever ≥39°C with purulent discharge for ≥3 consecutive days) 1

Do not use fluoroquinolones as first-line therapy in patients without documented β-lactam allergies, as this promotes antimicrobial resistance 1

Do not use first-generation cephalosporins (cephalexin) due to inadequate coverage against H. influenzae 1

Ensure adequate treatment duration: minimum 5 days for adults and 10 days for children to prevent relapse 1, 5