What is the best empiric antibiotic for an adult with a documented amoxicillin‑clavulanate (Augmentin) allergy who presents with cough, purulent sputum, and exudative pharyngitis?

Best Antibiotic for Augmentin-Allergic Patient with Exudative Pharyngitis and Productive Cough

For a patient with documented amoxicillin-clavulanate allergy presenting with exudative pharyngitis and purulent sputum, prescribe a narrow-spectrum oral cephalosporin (cephalexin or cefadroxil) for 10 days if the allergy is not anaphylactic-type, or clindamycin if there is a history of immediate hypersensitivity. 1

Clinical Reasoning and Antibiotic Selection Algorithm

Step 1: Determine the Type of Penicillin Allergy

• If the allergy is non-anaphylactic (rash, mild GI upset): A narrow-spectrum oral cephalosporin is the preferred choice, as up to 90% of penicillin-allergic patients can safely tolerate cephalosporins 1
• If the allergy involves immediate/anaphylactic-type hypersensitivity (angioedema, bronchospasm, urticaria within minutes): Avoid all beta-lactams including cephalosporins, as up to 10% will have cross-reactivity 1

Step 2: Address the Exudative Pharyngitis Component

The exudative pharyngitis suggests Group A Streptococcal infection, which requires specific antibiotic coverage:

• First-line for non-anaphylactic penicillin allergy: Cephalexin or cefadroxil for 10 days 1, 2

  • These narrow-spectrum cephalosporins are strongly preferred over broad-spectrum agents (cefdinir, cefuroxime, cefixime) to minimize resistance selection 1
  • The 10-day duration is essential for adequate GAS eradication and rheumatic fever prevention 2

• For anaphylactic-type allergy: Clindamycin is the most appropriate alternative 1

  • Clindamycin resistance among GAS isolates in the United States is approximately 1%, making it highly reliable 1
  • It is FDA-indicated for serious streptococcal infections in penicillin-allergic patients 3

• Macrolides (azithromycin, clarithromycin) are less preferred: While guideline-endorsed alternatives, macrolide resistance rates among pharyngeal GAS isolates range from 5-8% in most U.S. areas, with treatment failure rates of 20-25% 1, 2

Step 3: Consider the Productive Cough Component

The yellow/purulent sputum with cough likely represents acute bronchitis, which is viral in >90% of cases:

• Do not prescribe antibiotics specifically for the bronchitis component unless pneumonia is suspected 1
• Assess for pneumonia by checking for: tachycardia (>100 bpm), tachypnea (>24 breaths/min), fever (>38°C), and abnormal chest examination findings (rales, egophony, fremitus) 1
• If all four criteria are absent in an immunocompetent adult <70 years, pneumonia is unlikely and the cough requires only symptomatic management 1
• Purulent sputum color does not indicate bacterial infection—it reflects inflammatory cells and sloughed epithelial cells, not bacteria 1

Step 4: Final Antibiotic Recommendation

For non-anaphylactic Augmentin allergy:

• Cephalexin 500 mg orally twice daily for 10 days, OR
• Cefadroxil 1 g orally once daily for 10 days 1

For anaphylactic-type Augmentin allergy:

• Clindamycin 300 mg orally three times daily for 10 days 1, 3

Critical Pitfalls to Avoid

• Do not use fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin): Older fluoroquinolones have limited GAS activity, and newer ones are unnecessarily broad-spectrum and expensive for routine pharyngitis 1
• Do not use trimethoprim-sulfamethoxazole or tetracyclines: These agents do not eradicate GAS and should never be used for streptococcal pharyngitis 1
• Do not prescribe antibiotics for the cough alone: The productive cough is almost certainly viral bronchitis and will not benefit from antibiotics, only increasing adverse effects 1
• Do not use broad-spectrum cephalosporins (cefdinir, cefuroxime, cefpodoxime): These are more expensive and promote antibiotic resistance compared to narrow-spectrum agents 1

Reassessment Timeline

• Evaluate clinical response at 72 hours 2
• If symptoms worsen or fail to improve, consider treatment failure and alternative diagnoses 2
• Complete the full 10-day course even if symptoms resolve earlier to prevent rheumatic fever and ensure GAS eradication 2