What antibiotics are recommended for an adult patient with a bacterial upper respiratory infection, considering potential penicillin allergy and impaired renal function?

Antibiotics Are Generally NOT Recommended for Upper Respiratory Infections

Most upper respiratory infections (URIs) are viral and do not benefit from antibiotics—prescribing them causes harm without clinical benefit. 1, 2, 3

When Antibiotics Should NOT Be Used

The overwhelming majority of URIs are viral and resolve spontaneously within 7-10 days without antibiotic therapy. 1, 2, 3

Antibiotics are explicitly contraindicated for:

• Common cold (viral rhinitis) 2, 4
• Influenza 2
• COVID-19 2
• Laryngitis 2
• Nonspecific upper respiratory tract infections/acute rhinopharyngitis 3

Critical evidence: Antibiotic therapy for viral URIs does not shorten illness duration, does not prevent secondary bacterial infections, and only adds patient expense and risk of adverse reactions. 5, 3

The Rare Exception: Acute Bacterial Sinusitis

Only 0.5-2% of acute rhinosinusitis progresses to bacterial infection requiring antibiotics. 1

Antibiotics should ONLY be prescribed when acute bacterial rhinosinusitis (ABRS) is confirmed by one of three criteria: 6, 7

• Persistent symptoms ≥10 days without improvement
• Severe symptoms (fever ≥39°C with purulent nasal discharge and facial pain) for ≥3 consecutive days
• "Double sickening" - worsening after initial improvement from a viral URI

First-Line Antibiotic for Confirmed Bacterial Sinusitis

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line agent for adults with confirmed ABRS. 6, 7

For Penicillin Allergy (Non-Severe)

Second- or third-generation cephalosporins are appropriate alternatives: 6

• Cefuroxime-axetil
• Cefpodoxime-proxetil
• Cefdinir

The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible in non-Type I allergies. 6

For Severe Penicillin Allergy (Anaphylaxis)

Respiratory fluoroquinolones should be reserved for documented severe β-lactam allergies: 6, 7

• Levofloxacin 500 mg once daily for 10 days 6, 8
• Moxifloxacin 400 mg once daily for 10 days 6

These provide 90-92% predicted clinical efficacy against drug-resistant Streptococcus pneumoniae and β-lactamase-producing Haemophilus influenzae. 6

Renal Dosing Adjustments

For levofloxacin in patients with impaired renal function, the FDA label provides specific guidance: 8

• The pharmacokinetics of levofloxacin are affected by renal impairment
• Dosage adjustments are required based on creatinine clearance
• Consult the full prescribing information for specific renal dosing recommendations

Essential Adjunctive Therapies (For All Patients)

These should be offered regardless of antibiotic use: 6, 7

• Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily) - reduce inflammation and improve symptom resolution
• Saline nasal irrigation - provides symptomatic relief
• Analgesics (acetaminophen or ibuprofen) - for pain and fever
• Adequate hydration

Critical Pitfalls to Avoid

Do NOT prescribe antibiotics for symptoms lasting <10 days unless severe features are present (fever ≥39°C with purulent discharge for ≥3 consecutive days). 1, 6, 7

Purulent nasal discharge alone does NOT indicate bacterial infection - this is commonly observed in viral URIs and does not predict benefit from antibiotics. 3

Azithromycin and other macrolides should NEVER be used for respiratory infections due to resistance rates exceeding 20-25% for both S. pneumoniae and H. influenzae. 6

First-generation cephalosporins (cephalexin) are inappropriate due to inadequate coverage against Haemophilus influenzae. 6

Reassessment Timeline

If antibiotics are prescribed for confirmed ABRS: 6, 7

• Reassess at 3-5 days - if no improvement, switch to second-line therapy
• Reassess at 7 days - if symptoms persist or worsen, reconfirm diagnosis and consider complications
• Most patients should show noticeable improvement within 3-5 days of appropriate antibiotic therapy

The Bottom Line

The vast majority of URIs (98-99.5%) are viral and resolve spontaneously without antibiotics. 1, 7 Inappropriate antibiotic prescribing contributes to antimicrobial resistance, causes adverse effects, and adds unnecessary costs without clinical benefit. 1, 2, 5 Reserve antibiotics exclusively for the rare cases of confirmed acute bacterial sinusitis meeting strict diagnostic criteria. 1, 6, 7