What is the appropriate diagnosis and treatment for a patient with pharyngitis?

Diagnosis and Treatment of Pharyngitis

Diagnostic Approach: Confirm Group A Streptococcus Before Treating

Do not prescribe antibiotics for pharyngitis without confirming Group A Streptococcus (GAS) infection through testing, as the vast majority of adult pharyngitis is viral and self-limited. 1

Clinical Screening Algorithm

Use the Centor criteria to determine who needs testing 1, 2:

• History of fever
• Tonsillar exudates
• Absence of cough
• Tender anterior cervical lymphadenopathy

Testing strategy based on Centor criteria:

• 0-1 criteria: Do not test or treat—viral etiology most likely 1, 2
• 2-3 criteria: Perform rapid antigen detection test (RADT); treat only if positive 1, 2
• 4 criteria: Either perform RADT or treat empirically (acceptable alternative) 1, 2

Important Testing Considerations

• Children and adolescents: Back up negative RADTs with throat culture due to higher risk of acute rheumatic fever 1, 3
• Adults: Backup cultures after negative RADT are not necessary given low incidence of complications 1, 3
• Children <3 years: Do not test routinely unless special risk factors exist (e.g., older sibling with GAS), as acute rheumatic fever is rare and classic presentation uncommon in this age group 1

Common pitfall: Viral pharyngitis features that should prompt you NOT to test include cough, rhinorrhea, hoarseness, conjunctivitis, and oral ulcers 1

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First-Line Antibiotic Treatment for Confirmed GAS Pharyngitis

Penicillin or amoxicillin for 10 days is the treatment of choice for all non-allergic patients with confirmed GAS pharyngitis. 1, 4, 3

Specific Dosing Regimens

Adults:

• Penicillin V: 500 mg orally twice daily for 10 days 1, 4
• Amoxicillin: 1000 mg once daily for 10 days (preferred for adherence) 1, 4

Children:

• Amoxicillin: 50 mg/kg once daily (maximum 1000 mg) for 10 days 1, 4
• Alternative: 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1
• Penicillin V: 250 mg 2-3 times daily for 10 days 1

Intramuscular option (if adherence concerns):

• Benzathine penicillin G: 1.2 million units IM as single dose (adults and children ≥27 kg) 1, 4
• 600,000 units IM for children <27 kg 1

Why These Remain First-Line

Penicillin and amoxicillin are preferred based on 1:

• Proven efficacy in preventing acute rheumatic fever
• Narrow spectrum of activity
• No documented resistance of GAS to penicillin anywhere in the world
• Low cost
• Minimal adverse effects

Critical requirement: The full 10-day course is mandatory to achieve maximal pharyngeal eradication and prevent acute rheumatic fever—shortening by even a few days increases treatment failure rates 1, 4

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Treatment for Penicillin-Allergic Patients

Determine Type of Allergic Reaction First

The type of penicillin allergy dictates which alternatives are safe:

Non-immediate/non-anaphylactic reactions (delayed rash, mild reactions):

• First-generation cephalosporins are preferred with only 0.1% cross-reactivity risk 5
• Cephalexin: 500 mg twice daily for 10 days (adults) or 20 mg/kg/dose twice daily for 10 days (children, max 500 mg/dose) 1, 5
• Cefadroxil: 1 gram once daily for 10 days (adults) or 30 mg/kg once daily for 10 days (children, max 1 gram) 1, 5

Immediate/anaphylactic reactions (anaphylaxis, angioedema, urticaria within 1 hour, bronchospasm):

• Avoid ALL beta-lactams including cephalosporins due to up to 10% cross-reactivity 1, 5
• Clindamycin is the preferred choice: 300 mg three times daily for 10 days (adults) or 7 mg/kg/dose three times daily for 10 days (children, max 300 mg/dose) 1, 5
• Clindamycin has only ~1% resistance among GAS in the United States and demonstrates superior eradication even in chronic carriers 1, 5

Alternative macrolides for immediate allergy:

• Azithromycin: 500 mg once daily for 5 days (adults) or 12 mg/kg once daily for 5 days (children, max 500 mg) 1, 5, 6
• Clarithromycin: 250 mg twice daily for 10 days (adults) or 7.5 mg/kg/dose twice daily for 10 days (children, max 250 mg/dose) 1, 5

Important Resistance Considerations

Macrolide resistance is 5-8% in the United States and varies geographically, making clindamycin more reliable when beta-lactams cannot be used 1, 5. Azithromycin is the only antibiotic requiring just 5 days due to prolonged tissue half-life, but this shorter duration comes with higher resistance concerns 1, 5, 6.

Common pitfall: Do not assume all penicillin-allergic patients need macrolides or clindamycin—most patients with non-immediate reactions can safely receive first-generation cephalosporins 5

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Adjunctive Symptomatic Treatment

Offer analgesics/antipyretics to ALL patients with pharyngitis regardless of etiology:

• Acetaminophen or NSAIDs (ibuprofen) for moderate to severe symptoms or high fever 1, 3
• NSAIDs are more effective than acetaminophen for fever and pain control 3
• Aspirin must be avoided in children due to Reye syndrome risk 1, 3
• Corticosteroids are NOT recommended as adjunctive therapy 1

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Post-Treatment and Follow-Up

Routine post-treatment throat cultures or RADTs are NOT recommended for asymptomatic patients who have completed therapy 1, 3. Testing should only be considered in special circumstances such as patients with history of rheumatic fever 1.

Do not test or treat asymptomatic household contacts of patients with GAS pharyngitis 1, 3.

Recurrent Pharyngitis

For patients with recurrent episodes of pharyngitis with positive GAS testing, consider two possibilities 1:

• Multiple true GAS infections occurring at close intervals
• Chronic GAS carrier experiencing repeated viral infections

Chronic carriers generally do not require treatment, as they are unlikely to spread GAS and are at little risk for complications 1. For confirmed treatment failures or chronic carriers requiring eradication, clindamycin demonstrates substantially higher eradication rates than penicillin 1, 5.

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Critical Pitfalls to Avoid

• Do not treat without confirming diagnosis—clinical features alone cannot distinguish bacterial from viral pharyngitis 3, 7
• Do not shorten antibiotic courses below 10 days (except azithromycin's 5-day regimen)—this dramatically increases treatment failure and rheumatic fever risk 1, 4
• Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions—cross-reactivity risk is 10% 1, 5
• Do not prescribe broad-spectrum antibiotics when narrow-spectrum agents are appropriate 1, 3
• Do not use trimethoprim-sulfamethoxazole (Bactrim) for strep throat—sulfonamides do not eradicate GAS 5