What antibiotics are recommended for treating bacterial sinusitis?

Antibiotic Treatment for Bacterial Sinusitis

High-dose amoxicillin-clavulanate is the preferred first-line antibiotic for bacterial sinusitis in both adults and children, with treatment duration of 5-7 days for uncomplicated cases being as effective as 10-14 days with fewer adverse effects. 1, 2

First-Line Therapy Selection

Adults

• Amoxicillin-clavulanate is the preferred agent for adults with bacterial sinusitis due to its effectiveness against beta-lactamase-producing strains of Haemophilus influenzae and Moraxella catarrhalis, which account for a significant proportion of cases 1, 2
• Levofloxacin 500 mg once daily for 5-10 days is FDA-approved for acute bacterial sinusitis and provides an alternative for treatment failures or penicillin-allergic patients 3
• Treatment duration of 5-7 days is as effective as 10-14 days for uncomplicated cases with fewer adverse effects 1

Children

• Standard-dose amoxicillin (45 mg/kg/day divided twice daily) is appropriate for children ≥2 years with no recent antibiotic exposure, not attending daycare, and with mild-to-moderate disease 2, 4
• High-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day of clavulanate in 2 divided doses) is recommended for children with risk factors: age <2 years, daycare attendance, recent antibiotic use within 4 weeks, or high local prevalence of resistant S. pneumoniae 2, 4
• Treatment duration should be 10-14 days in children to ensure complete eradication of pathogens 2, 4

Risk Factors Requiring High-Dose Therapy

The following risk factors mandate high-dose amoxicillin-clavulanate rather than standard dosing:

• Recent antibiotic use within 4-6 weeks 1
• Age >65 years or <2 years 1, 2
• Diabetes or chronic comorbidities 1
• Immunocompromised status 1
• Close contact with daycare children 1

Alternative Therapy for Penicillin Allergy

Non-Type I Hypersensitivity (Non-Severe Allergy)

• Second or third-generation cephalosporins are appropriate: cefuroxime axetil, cefpodoxime, or cefdinir 2
• Cefuroxime axetil or cefprozil provide significantly enhanced activity against beta-lactamase-producing M. catarrhalis with twice-daily dosing 1

Type I Hypersensitivity (Severe/True Penicillin Allergy)

• Levofloxacin 500 mg once daily for 5-10 days is the preferred alternative for adults with true penicillin allergy 1, 3
• Moxifloxacin 400 mg once daily for 5-10 days is equally effective 1
• Fluoroquinolones should be reserved for treatment failures or true penicillin allergy to prevent promoting resistance, not used as first-line therapy for uncomplicated cases 1

What NOT to Use

Ineffective Agents

• Plain amoxicillin should NOT be used due to ineffectiveness against 90-100% of M. catarrhalis strains that produce beta-lactamase 1
• Beta-lactamase production cannot be overcome by dose escalation of amoxicillin alone 1
• First-generation cephalosporins (cephalexin, cefadroxil) have poor coverage for M. catarrhalis and should be avoided 1
• Cefaclor has inadequate activity against all beta-lactamase-producing M. catarrhalis and is associated with high risk of serum sickness-like reactions 1

Suboptimal Agents

• Azithromycin or clarithromycin have predicted clinical efficacy of only 77-81% with bacterial failure rates of 20-25% possible, and should not be used as first-line therapy 1
• These macrolides may be considered only in cases of serious drug allergy when other options are not feasible 5

Management of Treatment Failure

72-Hour Reassessment

• Reassess at 72 hours - if symptoms worsen or fail to improve, change to second-line therapy 2, 4
• Only 9% of placebo-treated children improve between days 3-10 after failing at day 3, making reassurance alone inadequate 4
• Treatment failure at 72 hours predicts continued failure without intervention 4

Second-Line Options

• For children failing amoxicillin monotherapy, switch to high-dose amoxicillin-clavulanate 2, 4
• For adults or children failing amoxicillin-clavulanate, respiratory fluoroquinolones (levofloxacin or moxifloxacin) have 90-92% predicted clinical efficacy and are the preferred second-line agents 2
• Ceftriaxone 1 g IM/IV daily for 5 days (adults) or 50 mg/kg IM/IV once daily (children) is an alternative therapy 1, 4

When to Refer to ENT

• ENT referral is NOT indicated for uncomplicated treatment failure at 72 hours 4
• Referral becomes necessary when the patient fails second-line antibiotic therapy or develops complications 4

Red Flags Requiring Immediate Action

The following signs require immediate imaging and specialist consultation with initiation of IV antibiotics:

• Periorbital or orbital swelling 4
• Impaired extraocular muscle function 4
• Impaired visual acuity 4
• Severe headache 4
• Altered mental status 4
• Seizures 4
• Focal neurologic findings 4
• Initiate IV vancomycin plus ceftriaxone or cefotaxime immediately for suspected orbital or intracranial complications 4

Special Populations

Nosocomial Sinusitis

• Commonly caused by gram-negative bacilli, S. aureus, and anaerobes, requiring broader coverage 2
• Consider Pseudomonas aeruginosa in immunocompromised patients and those with nasal tubes, catheters, or intubation 6

Immunocompromised Patients

• Fungal sinusitis should be considered and may require specific antifungal therapy and surgical debridement 2

Adjunctive Therapy

• Intranasal corticosteroids can reduce inflammation and may provide additional benefit when used alongside antibiotics, but should not replace antimicrobial therapy 2, 4
• Saline irrigation can improve mucociliary clearance 2

Critical Pitfalls to Avoid

• Never use plain amoxicillin, even at high doses, as beta-lactamase production cannot be overcome by dose escalation 1
• Do not obtain imaging studies (CT or MRI) for uncomplicated treatment failure at 72 hours, as imaging does not contribute to diagnosis in straightforward cases 4
• Ensure the diagnosis of bacterial sinusitis was correct initially before escalating therapy 4
• Avoid fluoroquinolones as first-line therapy to preserve their effectiveness for treatment failures and resistant cases 1