Antibiotic Treatment for Bacterial Upper Respiratory Infections in Adults
Most upper respiratory infections (URIs) are viral and do not require antibiotics; however, when bacterial infection is confirmed (such as acute bacterial rhinosinusitis), amoxicillin-clavulanate is the preferred first-line antibiotic for otherwise healthy adults. 1
Critical First Step: Distinguish Viral from Bacterial Infection
The vast majority (>90%) of URIs are viral and antibiotics provide no benefit. 1, 2 Antibiotics should be reserved only for confirmed bacterial infections. 1
For Acute Bacterial Rhinosinusitis (ABRS)
Bacterial infection is likely when any of these criteria are met: 1
- Persistent symptoms for >10 days without clinical improvement
- Severe symptoms (fever >39°C, purulent nasal discharge, or facial pain) lasting ≥3 consecutive days
- "Double sickening" - worsening symptoms after initial improvement for >3 days
Preferred Antibiotic Selection
First-Line Treatment
Amoxicillin-clavulanate is the preferred agent when antibiotics are indicated for ABRS. 1 The IDSA 2012 guidelines specifically recommend this combination over amoxicillin alone, though some societies (American Academy of Family Physicians, American Academy of Allergy, Asthma & Immunology) favor plain amoxicillin. 1
Dosing: For respiratory tract infections, use 875 mg/125 mg every 12 hours or 500 mg/125 mg every 8 hours. 3
Alternative Options
For patients with penicillin allergy or contraindications: 1
- Doxycycline (tetracycline class)
- Respiratory fluoroquinolone (levofloxacin or moxifloxacin)
Important Caveats and Pitfalls
Watchful Waiting is Often Appropriate
The American Academy of Otolaryngology–Head and Neck Surgery emphasizes watchful waiting without antibiotics as initial management for all patients with uncomplicated ABRS, regardless of severity. 1 This reflects the self-limited nature of most cases.
Number Needed to Treat vs. Harm
A meta-analysis showed that for acute rhinosinusitis: 1
- Number needed to treat = 18 (for one patient to be cured rapidly)
- Number needed to harm = 8 (for adverse effects from antibiotics)
This means most patients have more adverse effects than benefits from antibiotics. 1
Purulent Secretions Do Not Indicate Bacterial Infection
Purulent nasal discharge alone does not predict bacterial infection or benefit from antibiotics. 2 Purulence results from inflammatory cells and sloughed epithelial cells, not necessarily bacteria. 1
Imaging is Not Helpful
Radiographic imaging has no role in determining bacterial versus viral cause and would increase costs 4-fold without improving diagnostic accuracy. 1
Adjunctive Therapy
Consider these supportive measures regardless of antibiotic use: 1
- Intranasal saline irrigation
- Intranasal corticosteroids
- Analgesics for pain
- Antipyretics for fever
These have been shown to alleviate symptoms and potentially decrease antibiotic use. 1
When to Refer to a Specialist
Refer patients who are: 1
- Seriously ill
- Deteriorating clinically despite antibiotic therapy
- Having recurrent episodes
Appropriate specialists include otolaryngologists, infectious disease specialists, or allergists. 1
Treatment Duration
When antibiotics are prescribed, typical duration is 5-7 days for uncomplicated cases. 4, 5