What oral antibiotic can I use for streptococcal pharyngitis (strep throat)?

Oral Antibiotic Treatment for Streptococcal Pharyngitis

Penicillin V (250 mg orally twice daily for 10 days) or amoxicillin (750 mg once daily for 10 days) remains the first-line oral antibiotic for strep throat due to proven efficacy, safety, narrow spectrum, and low cost, with no documented resistance anywhere in the world. 1

First-Line Treatment Options

Penicillin V is the gold standard for treating streptococcal pharyngitis when oral therapy is appropriate 1. The recommended dosing is:

• Adults and children: 250 mg orally twice daily for 10 days 1, 2
• Alternative: Amoxicillin 750 mg once daily for 10 days offers comparable efficacy with improved compliance due to once-daily dosing 3

The full 10-day course is essential to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever 1, 4.

Alternative Antibiotics for Penicillin Allergy

For Non-Immediate (Non-Anaphylactic) Penicillin Allergy

First-generation cephalosporins are the preferred alternatives with strong, high-quality evidence 4, 5, 6:

• Cephalexin: 500 mg orally twice daily for 10 days (adults) or 20 mg/kg per dose twice daily for 10 days (children, maximum 500 mg/dose) 4, 6
• Cefadroxil: 1 gram once daily for 10 days (adults) or 30 mg/kg once daily for 10 days (children, maximum 1 gram) 4, 6

The cross-reactivity risk with first-generation cephalosporins is only 0.1% in patients with non-severe, delayed penicillin reactions 4.

For Immediate/Anaphylactic Penicillin Allergy

All beta-lactam antibiotics must be avoided due to up to 10% cross-reactivity risk 1, 4. Use these alternatives:

Clindamycin is the preferred choice with strong, moderate-quality evidence 4, 6:

• Dosing: 300 mg orally three times daily for 10 days (adults) or 7 mg/kg per dose three times daily for 10 days (children, maximum 300 mg/dose) 4, 6
• Advantages: Only ~1% resistance rate among Group A Streptococcus in the United States 4, 6
• Special benefit: Particularly effective in chronic carriers and recurrent infections 1, 6

Azithromycin is an acceptable alternative 4, 6, 7:

• Dosing: 500 mg once daily for 5 days (adults) or 12 mg/kg once daily for 5 days (children, maximum 500 mg) 4, 6, 7
• Unique feature: Only antibiotic requiring just 5 days due to prolonged tissue half-life 1, 4, 6
• Important caveat: Macrolide resistance is 5-8% in the United States and varies geographically 4, 6
• FDA note: Some strains are resistant to azithromycin; susceptibility testing should be performed when possible 7

Clarithromycin is also acceptable 4, 6:

• Dosing: 250 mg orally twice daily for 10 days (adults) or 7.5 mg/kg per dose twice daily for 10 days (children, maximum 250 mg/dose) 4, 6
• Evidence: 10 days of clarithromycin was more effective than 5 days of azithromycin in eradicating Group A Streptococcus (91% vs 82%, P=0.012) 8

Erythromycin is less preferred due to high gastrointestinal side effects but remains an option 1, 5:

• Dosing: 250-500 mg every 6-12 hours for 10 days (adults) or 20-40 mg/kg/day divided 2-3 times daily for 10 days (children, maximum 1 gram/day) 4

Critical Treatment Duration Requirements

All antibiotics except azithromycin require a full 10-day course to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 1, 4, 6. Shortening the course by even a few days results in appreciable increases in treatment failure rates 4.

Azithromycin is the only exception, requiring just 5 days due to its unique pharmacokinetics and prolonged tissue half-life 1, 4, 6, 7.

Common Pitfalls to Avoid

• Never use cephalosporins in patients with immediate/anaphylactic penicillin reactions due to 10% cross-reactivity risk 1, 4
• Do not prescribe shorter courses than recommended (except azithromycin's 5-day regimen) as this leads to treatment failure and complications 4
• Be aware of local macrolide resistance patterns before prescribing azithromycin or clarithromycin, as resistance varies geographically 4, 6
• Do not use trimethoprim-sulfamethoxazole (Bactrim) for strep throat due to high resistance rates (50%) 4
• Avoid using broad-spectrum antibiotics as first-line when narrow-spectrum agents are appropriate, as this unnecessarily increases cost and selects for resistant flora 1

Post-Treatment Considerations

Routine follow-up throat cultures are not recommended for asymptomatic patients who have completed therapy 1, 6. Testing should only be considered in special circumstances, such as patients with a history of rheumatic fever 4, 6.