What is the first-line therapy for acute pharyngitis in a healthy adult or child, including diagnostic testing and options for penicillin-allergic patients?

First-Line Treatment for Throat Infection

For confirmed Group A Streptococcal pharyngitis, penicillin or amoxicillin for 10 days is the definitive first-line treatment, offering proven efficacy in preventing acute rheumatic fever, narrow-spectrum activity, excellent safety, and no documented resistance worldwide. 1

Diagnostic Approach Before Treatment

Do not prescribe antibiotics based on clinical appearance alone—laboratory confirmation is mandatory because only 5-15% of adult pharyngitis and 20-30% of pediatric cases are actually caused by Group A Streptococcus (GAS). 1

When to Test for Streptococcal Infection

• Test only when clinical features suggest bacterial rather than viral etiology: sudden-onset sore throat, fever, tonsillar exudates, tender anterior cervical lymphadenopathy, and absence of viral features (cough, rhinorrhea, hoarseness, conjunctivitis). 1
• Do not test when viral features dominate—cough, rhinorrhea, and conjunctivitis strongly indicate viral pharyngitis, and testing will likely identify harmless GAS carriers rather than true infection. 1
• Children under 3 years should not be tested except when an older sibling has confirmed GAS infection, because GAS pharyngitis and rheumatic fever are rare in this age group. 1

Testing Strategy by Age

• Children and adolescents: Perform rapid antigen detection test (RADT) first; if negative, follow with throat culture because RADT sensitivity is only 80-90% and misses 10-20% of true infections. 1
• Adults: RADT alone is sufficient—a negative result does not require backup throat culture due to low GAS prevalence (5-10%) and extremely low rheumatic fever risk in adults. 1

First-Line Antibiotic Treatment for Confirmed GAS

Standard Regimens (Non-Allergic Patients)

Penicillin or amoxicillin for a full 10 days is mandatory to achieve maximal pharyngeal eradication and prevent acute rheumatic fever, even if symptoms resolve in 3-4 days. 1, 2

• Penicillin V: 250 mg orally 2-3 times daily for children <27 kg; 500 mg orally 2-3 times daily for children ≥27 kg and adults, for 10 days. 1
• Amoxicillin: 50 mg/kg once daily (maximum 1 g) for 10 days in children; 500 mg twice daily for adults. 1, 2
• Benzathine penicillin G (intramuscular): Single dose of 600,000 units for patients <27 kg; 1,200,000 units for patients ≥27 kg—use when oral compliance is questionable. 1

Amoxicillin is preferred over penicillin V in younger children due to better palatability and availability as suspension, although both have identical efficacy. 2

Treatment for Penicillin-Allergic Patients

Non-Anaphylactic (Delayed) Penicillin Allergy

First-generation cephalosporins are the preferred alternative with strong, high-quality evidence—the cross-reactivity risk is only 0.1% in patients with non-severe, delayed reactions. 2

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days in children; 500 mg twice daily for 10 days in adults. 2
• Cefadroxil: 30 mg/kg once daily (maximum 1 g) for 10 days. 2

Immediate/Anaphylactic Penicillin Allergy

Avoid all beta-lactam antibiotics (including cephalosporins) due to up to 10% cross-reactivity risk in patients with anaphylaxis, angioedema, or immediate urticaria. 2

Clindamycin is the preferred choice with only ~1% resistance among GAS in the United States and demonstrated high efficacy even in chronic carriers. 2, 3

• Clindamycin: 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days in children; 300 mg three times daily for 10 days in adults. 2

Alternative macrolides (use only when clindamycin is unavailable or contraindicated):

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days—the only antibiotic requiring just 5 days due to prolonged tissue half-life. 2
• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days. 2

Be aware that macrolide resistance is 5-8% in the United States and varies geographically, making clindamycin more reliable when beta-lactams cannot be used. 2

Management When Strep Test is Negative

Withhold antibiotics entirely and provide only symptomatic treatment—the vast majority of strep-negative pharyngitis is viral and self-limited. 1

Symptomatic Treatment for All Patients

• Ibuprofen or acetaminophen for pain and fever relief—both are effective with moderate-to-strong evidence. 1
• Avoid aspirin in children due to Reye syndrome risk. 2
• Throat lozenges can provide additional comfort. 1
• Reassure patients that symptoms typically resolve in less than 1 week without antibiotics. 1

Critical Pitfalls to Avoid

• Do not shorten the antibiotic course below 10 days (except azithromycin's 5-day regimen)—even a few days' reduction dramatically increases treatment failure and rheumatic fever risk. 1, 2
• Do not test or treat asymptomatic household contacts—up to one-third are harmless GAS carriers, and prophylactic treatment does not reduce subsequent infection rates. 1
• Do not perform routine follow-up testing after completing therapy in asymptomatic patients—positive post-treatment tests often reflect carrier status rather than treatment failure. 1
• Do not use trimethoprim-sulfamethoxazole (Bactrim)—it fails to eradicate GAS in 20-25% of cases and should never be prescribed for streptococcal pharyngitis. 2

Why These Recommendations Matter

Antibiotics shorten symptom duration by only 1-2 days (number needed to treat = 6 at 3 days, 21 at 1 week), but the primary justification for treating confirmed GAS is preventing acute rheumatic fever, which can be prevented when treatment is initiated within 9 days of symptom onset. 1, 4 Antibiotics do not prevent post-streptococcal glomerulonephritis. 1

Up to 70% of patients with sore throats receive unnecessary antibiotic prescriptions, while only 20-30% actually have GAS pharyngitis—this massive overtreatment drives antibiotic resistance and exposes patients to unnecessary adverse effects. 1