What is the oral antibiotic of choice for strep throat?

Oral Antibiotic of Choice for Strep Throat

Penicillin V or amoxicillin are the first-line oral antibiotics for strep throat, with penicillin V dosed at 250 mg twice or three times daily for children, or 250 mg four times daily (or 500 mg twice daily) for adolescents and adults, all for 10 days. 1

First-Line Treatment for Non-Allergic Patients

Penicillin V remains the drug of choice because of its proven efficacy, safety, narrow spectrum of activity, and low cost. 1 The IDSA guidelines provide strong, high-quality evidence supporting this recommendation. 1

Amoxicillin is equally effective and often preferred in young children due to better palatability of the suspension. 1, 2 Dosing is 50 mg/kg once daily (maximum 1,000 mg) or 25 mg/kg twice daily (maximum 500 mg) for 10 days. 1

Key Dosing Details:

• Children: Penicillin V 250 mg twice or three times daily for 10 days 1
• Adolescents and adults: Penicillin V 250 mg four times daily OR 500 mg twice daily for 10 days 1
• Alternative: Amoxicillin with weight-based dosing as above 1

Treatment for Penicillin-Allergic Patients

For patients with non-immediate penicillin allergy, first-generation cephalosporins are appropriate:

• 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

Critical caveat: Avoid cephalosporins in patients with immediate-type hypersensitivity to penicillin. 1

For patients with immediate penicillin allergy or severe reactions:

• Clindamycin: 7 mg/kg/dose three times daily (maximum 300 mg/dose) for 10 days (strong, moderate evidence) 1
• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days (strong, moderate evidence) 1
• Clarithromycin: 7.5 mg/kg/dose twice daily (maximum 250 mg/dose) for 10 days (strong, moderate evidence) 1

Important Resistance Considerations:

Macrolide resistance (azithromycin, clarithromycin) varies geographically and temporally, with rates around 5-8% in the United States. 1, 3 Some studies report up to 2.2% of Group A streptococcal isolates being resistant to azithromycin at enrollment. 4 The FDA label explicitly states that susceptibility testing should be performed when treating with azithromycin. 5

Treatment Duration

A full 10-day course is required for most oral antibiotics to achieve maximal pharyngeal eradication of Group A streptococci. 1, 3 This is critical for preventing rheumatic fever and suppurative complications. 1

Azithromycin is the only exception, requiring only 5 days due to its prolonged tissue half-life. 1, 3

When to Use Intramuscular Therapy

Benzathine penicillin G (intramuscular) is preferred when compliance with oral therapy is uncertain:

• Dosing: <27 kg (60 lb): 600,000 units; ≥27 kg: 1,200,000 units as a single dose 1
• Specific situations: Poor and crowded inner-city populations, episodic medical care, lack of follow-up, areas where rheumatic fever remains prevalent 6

This remains the "gold standard" for assured compliance and consistently produces the highest cure rates. 6

Common Pitfalls to Avoid

Do not use sulfonamides or tetracyclines for Group A streptococcal pharyngitis due to high resistance rates and frequent treatment failures. 1, 3

Do not rely on azithromycin to prevent rheumatic fever without documented susceptibility, as data establishing efficacy in subsequent prevention of rheumatic fever are not available. 5

Penicillin treatment failure rates have increased from 2-10% in the early 1970s to approximately 30% by 2000, primarily due to poor compliance with the 10-day regimen. 7 Other contributing factors include reexposure to infected contacts, copathogenicity with beta-lactamase-producing bacteria, and eradication of protective pharyngeal flora. 7

Therapy can be safely delayed up to 9 days after symptom onset and still prevent rheumatic fever, allowing time for culture confirmation before initiating antibiotics. 1

Clinical Outcomes

Early treatment reduces symptom duration to less than 24 hours in most cases, decreases suppurative complications, limits disease spread, and permits earlier return to normal activities. 6 However, Group A streptococcal pharyngitis is self-limited, with fever and constitutional symptoms resolving spontaneously within 3-4 days even without treatment. 1