What is the treatment for strep throat and prevention of rheumatic fever?

Treatment of Strep Throat and Prevention of Rheumatic Fever

Penicillin remains the definitive treatment of choice for group A streptococcal pharyngitis to prevent rheumatic fever, with oral penicillin V (250 mg twice daily for children, 500 mg 2-3 times daily for adolescents/adults) or intramuscular benzathine penicillin G (600,000 units for <27 kg, 1,200,000 units for ≥27 kg) as first-line options for a full 10-day course. 1

Diagnosis Before Treatment

• Accurate diagnosis requires either a positive throat culture or rapid antigen detection test (RADT), as clinical presentation alone cannot reliably distinguish streptococcal from viral pharyngitis 1
• Adults can be diagnosed with RADT alone without backup culture confirmation, given the extremely low risk of rheumatic fever in this population 2
• Children should have negative RADT results confirmed with throat culture due to higher rheumatic fever risk 1

First-Line Treatment: Penicillin

Penicillin is the only antibiotic proven in controlled trials to prevent initial attacks of rheumatic fever and has never demonstrated resistance in group A streptococci anywhere in the world 1

Oral Penicillin V Dosing:

• Children: 250 mg twice daily for 10 days (or 250 mg three times daily) 1
• Adolescents and adults: 500 mg 2-3 times daily for 10 days 1
• Alternative pediatric dosing: 40 mg/kg/day in 3 divided doses (not to exceed 750 mg for those weighing ≥27 kg) 1

Intramuscular Benzathine Penicillin G:

• <27 kg: 600,000 units as a single injection 1
• ≥27 kg: 1,200,000 units as a single injection 1
• Warming to room temperature before administration reduces injection discomfort 3

When to Choose Intramuscular Over Oral:

Strongly consider intramuscular benzathine penicillin G for: 3

• Patients unlikely to complete 10-day oral course
• Personal or family history of rheumatic fever or rheumatic heart disease
• High-risk environmental factors (crowded living conditions, limited healthcare access)
• Populations where rheumatic fever remains prevalent 4

Amoxicillin as Alternative:

• 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1
• Often preferred over penicillin V in young children due to better taste acceptance 1
• Equivalent efficacy to penicillin V 1

Penicillin-Allergic Patients

For patients with documented penicillin allergy, alternative regimens include:

First-Generation Cephalosporins (avoid in immediate-type hypersensitivity):

• Cephalexin: 20 mg/kg/dose twice daily (maximum 500 mg/dose) for 10 days 1
• Cefadroxil: 30 mg/kg once daily (maximum 1 g) for 10 days 1

Macrolides (check local resistance patterns):

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 5
• Clarithromycin: 7.5 mg/kg/dose twice daily (maximum 250 mg/dose) for 10 days 1
• Erythromycin: Indicated for penicillin-allergic patients, dosed according to formulation 6

Clindamycin:

• 7 mg/kg/dose three times daily (maximum 300 mg/dose) for 10 days 1

Critical Considerations for Macrolides

Important caveat: 10 days of clarithromycin therapy achieves significantly higher bacteriologic eradication rates (91%) compared to 5 days of azithromycin (82%) 7

• Macrolide resistance in group A streptococci remains <5% in the United States but varies geographically 1
• Azithromycin has NOT been proven to prevent rheumatic fever 5
• The FDA label explicitly states that "data establishing efficacy of azithromycin in subsequent prevention of rheumatic fever are not available" 5

Timing and Clinical Pearls

Treatment can be safely delayed up to 9 days after symptom onset and still effectively prevent rheumatic fever 1, 3

• This allows time for throat culture confirmation without increasing rheumatic fever risk 1
• Early treatment (within 24-48 hours) reduces symptom duration, decreases contagiousness, and allows faster return to normal activities 1
• Patients become non-contagious after 24 hours of antibiotic therapy 1, 3
• Even without treatment, symptoms typically resolve spontaneously within 3-4 days 1

Common Pitfalls to Avoid

Do not use broad-spectrum cephalosporins or fluoroquinolones as they are more expensive, promote antimicrobial resistance, and offer no advantage over narrow-spectrum penicillin 3

• Avoid shortening penicillin courses even by a few days, as this significantly increases treatment failure rates 1
• Do not rely on clinical improvement alone to assess treatment success, as streptococcal pharyngitis is self-limited 1
• Remember that at least one-third of rheumatic fever cases result from asymptomatic streptococcal infections, highlighting the importance of treating documented infections 2

Risk Context: Adults vs. Children

Initial attacks of acute rheumatic fever are extremely rare in adults, even with untreated streptococcal pharyngitis 2

• Group A streptococcal pharyngitis causes only 5-10% of acute pharyngitis in adults versus 15-30% in children 2
• Historically, up to 3% of untreated streptococcal pharyngitis cases in children were followed by rheumatic fever during epidemics 2
• Adults with prior rheumatic fever remain at high risk for recurrence and require continuous antimicrobial prophylaxis 2

Secondary Prevention After Rheumatic Fever

Patients who have had rheumatic fever require continuous antimicrobial prophylaxis to prevent recurrences: 3

• Benzathine penicillin G 1.2 million units intramuscularly every 4 weeks (or every 3 weeks in high-risk situations) 3
• Duration depends on cardiac involvement: at least 10 years or until age 40 (whichever is longer) for persistent valvular disease 3
• This represents secondary prophylaxis, not treatment of acute symptomatic episodes 3