What is the recommended dosing of amoxicillin (amoxicillin) for pharyngitis?

Amoxicillin Dosing for Group A Streptococcal Pharyngitis

For Group A streptococcal (GAS) pharyngitis, amoxicillin should be dosed at 50 mg/kg once daily (maximum 1000 mg) for 10 days, or alternatively 500 mg twice daily for adults and adolescents for 10 days. 1, 2

Recommended Dosing Regimens

Children:

• First-line option: 50 mg/kg once daily (maximum 1000 mg) for 10 days 1, 2
• Alternative option: 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1

Adolescents and Adults:

• First-line option: 1000 mg once daily for 10 days 2
• Alternative option: 500 mg twice daily for 10 days 1

Duration of Therapy

A full 10-day course of amoxicillin is strongly recommended to ensure bacterial eradication and prevent complications such as rheumatic fever, despite clinical improvement that typically occurs within 24-48 hours of starting therapy 1, 2.

Evidence Supporting Once-Daily Dosing

Several clinical trials have demonstrated that once-daily amoxicillin is as effective as multiple daily doses:

• A randomized, controlled, investigator-blinded trial showed that once-daily amoxicillin (750 mg or 1000 mg) was non-inferior to twice-daily dosing for GAS pharyngitis 3
• Another study demonstrated that once-daily amoxicillin (50 mg/kg/day) was as effective as traditional three-times-daily penicillin V in eradicating GAS 4
• A molecular biology study using PCR confirmed that once-daily dosing was as effective as BID or TID regimens in reducing bacterial load 5

Advantages of Amoxicillin Over Penicillin V

While penicillin V remains an acceptable first-line agent, amoxicillin offers several advantages:

• Better palatability (especially important for children)
• Convenient once-daily dosing that may improve adherence
• Comparable efficacy with potentially better bacteriologic cure rates 6
• Relatively inexpensive

Special Considerations

Penicillin-Allergic Patients

For patients with penicillin allergy, alternative treatments include:

• First-generation cephalosporins (if not anaphylactically sensitive): cephalexin 20 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1
• Clindamycin: 7 mg/kg three times daily (maximum 300 mg per dose) for 10 days 1
• Macrolides (azithromycin or clarithromycin): with caution due to variable resistance patterns 1

Common Pitfalls to Avoid

1. Inadequate duration: Do not shorten the 10-day course of amoxicillin, as this may increase the risk of rheumatic fever 2
2. Unnecessary broad-spectrum antibiotics: Avoid using broader-spectrum agents when amoxicillin is appropriate 1
3. Treating without testing: Confirm GAS pharyngitis with rapid antigen detection test or throat culture before initiating antibiotics 1, 2
4. Treating viral pharyngitis: Most cases of pharyngitis are viral and do not require antibiotics 1
5. Routine post-treatment testing: Follow-up cultures are not routinely needed if symptoms resolve 2

Recurrent Episodes

For patients with multiple recurrent episodes of GAS pharyngitis, consider alternative regimens such as:

• Clindamycin: 20-30 mg/kg/day in three doses (maximum 300 mg per dose) for 10 days 1
• Amoxicillin-clavulanate: 40 mg/kg/day of amoxicillin component in three doses for 10 days 1
• Penicillin with rifampin: Penicillin for 10 days plus rifampin for the last 4 days of treatment 1

Amoxicillin's once-daily dosing offers a significant advantage for improving patient adherence while maintaining excellent efficacy against GAS pharyngitis.