Can a patient with Group A streptococcal (GAS) infection be treated with amoxicillin if they were previously treated with amoxicillin less than one month ago?

From the Guidelines

It is generally not recommended to treat group A strep with amoxicillin if the patient was treated with the same antibiotic less than one month ago. Instead, consider alternative antibiotics such as clindamycin (300-450 mg orally three times daily for 10 days), azithromycin (500 mg on day 1, then 250 mg daily for 4 more days), or a cephalosporin like cefuroxime (250-500 mg twice daily for 10 days) 1. This recommendation stems from concerns about treatment failure and potential development of antibiotic resistance. When a patient has recently been exposed to amoxicillin, there's a higher likelihood that any remaining streptococcal bacteria may have developed reduced susceptibility to this antibiotic. Additionally, if the current infection represents a treatment failure or early recurrence of the previous infection, using the same antibiotic that was unsuccessful initially is unlikely to be effective. Some patients may also be carriers of group A strep rather than having a new infection, in which case different management approaches might be warranted.

Key Considerations

• The most recent and highest quality study recommends alternative antibiotics for patients who have been treated with amoxicillin less than one month ago 1.
• The Infectious Diseases Society of America guidelines suggest that amoxicillin is often used in place of oral penicillin V for young children, but its efficacy appears to be equal 1.
• The American Heart Association recommends that patients with acute streptococcal pharyngitis receive therapy with an antimicrobial agent in a dose and for a duration that is likely to eradicate the infecting organism from the pharynx 1.

Alternative Treatment Options

• Clindamycin (300-450 mg orally three times daily for 10 days) 1
• Azithromycin (500 mg on day 1, then 250 mg daily for 4 more days) 1
• Cefuroxime (250-500 mg twice daily for 10 days) 1

Important Notes

• No regimen eradicates GAS from the pharynx in 100% of treated patients, even though 100% of GAS demonstrate in vitro susceptibility to all-lactam agents (penicillins and cephalosporins) 1.
• The only currently recommended antimicrobial therapy that has been investigated in controlled studies and demonstrated to prevent initial attacks of acute rheumatic fever is intramuscular repository-penicillin therapy 1.

From the FDA Drug Label

To minimize the potential for gastrointestinal intolerance, amoxicillin should be taken at the start of a meal. It is recommended that there be at least 10 days’ treatment for any infection caused by Streptococcus pyogenes to prevent the occurrence of acute rheumatic fever.

The FDA drug label does not provide information on the use of amoxicillin in patients who were previously treated with amoxicillin less than 1 month ago. No conclusion can be drawn regarding the safety and efficacy of using amoxicillin to treat group A strep in this scenario 2.

From the Research

Treatment of Group A Strep with Amoxicillin

• The effectiveness of amoxicillin in treating Group A strep infections is supported by various studies 3, 4, 5.
• According to a study published in 1996, a 6-day course of amoxicillin was found to be as effective as a 10-day course of penicillin V in treating Group A beta-haemolytic streptococcal acute tonsillitis in adults 5.
• Another study published in 2003 notes that all isolates of Group A beta-hemolytic streptococcus (GABHS) are sensitive to penicillins, which includes amoxicillin, and that amoxicillin can be used as an alternative to penicillin V 3.
• However, the 2021 study highlights the importance of considering the mechanisms of antibiotic failure and the emergence of resistant strains, which may affect the efficacy of amoxicillin treatment 4.

Considerations for Previous Amoxicillin Treatment

• There is no direct evidence in the provided studies to suggest that amoxicillin treatment within the last month would affect its efficacy in treating a new Group A strep infection.
• However, the 2021 study mentions the emergence of strains with reduced susceptibility to β-lactams, including amoxicillin, which may be a concern in cases where the patient has been previously treated with amoxicillin 4.
• The 1996 study found that amoxicillin was effective in eradicating GABHS in adults, but it does not provide information on the impact of previous amoxicillin treatment on the efficacy of subsequent treatment 5.