From the Guidelines
If amoxicillin treatment fails for strep throat, the recommended next step is to switch to a different antibiotic, such as clindamycin (300mg three times daily for 10 days) or azithromycin (500mg on day 1, then 250mg daily for 4 more days), as these are typically effective alternatives 1. Treatment failure may occur due to several reasons, including patient non-compliance with the full course, bacterial resistance to amoxicillin, presence of beta-lactamase producing bacteria in the throat that inactivate amoxicillin, or because the patient is actually a strep carrier with a concurrent viral infection. Before switching antibiotics, it's essential to confirm that symptoms persist and that the patient completed the full initial course of amoxicillin (typically 500mg three times daily for 10 days) 1. Some key points to consider when selecting an alternative antibiotic include:
- Efficacy: The ability of the antibiotic to eradicate the bacteria causing the infection
- Safety: The potential side effects and risks associated with the antibiotic
- Antimicrobial spectrum: The range of bacteria that the antibiotic is effective against
- Dosing schedule: The frequency and duration of antibiotic administration
- Compliance: The likelihood that the patient will complete the full course of antibiotic treatment
- Cost: The financial burden of the antibiotic treatment In some cases, a combination therapy with amoxicillin-clavulanate (875/125mg twice daily for 10 days) may be used as it overcomes beta-lactamase resistance 1. Patients should complete the entire course of any antibiotic prescribed, even if symptoms improve, to prevent recurrence and complications like rheumatic fever 1. It's also important to note that some antibiotics, such as tetracyclines and sulfonamides, are not recommended for the treatment of strep throat due to high levels of resistance 1. Overall, the choice of alternative antibiotic should be based on the individual patient's needs and circumstances, and should take into account the potential benefits and risks of each option 1.
From the FDA Drug Label
Adults and Pediatric Patients Upper Respiratory Tract Infections of the Ear, Nose, and Throat:Amoxicillin for oral suspension is indicated in the treatment of infections due to susceptible (ONLY β-lactamase–negative) isolates of Streptococcusspecies. (α-and β-hemolytic isolates only),
- Amoxicillin treatment failure for strep throat can occur if the isolate is β-lactamase–positive or if the patient has a resistant strain of Streptococcus.
- The drug label does not provide information on the frequency or management of treatment failure.
- To minimize treatment failure, it is essential to use amoxicillin only for infections proven or strongly suspected to be caused by bacteria and to consider culture and susceptibility information when available 2.
From the Research
Amoxicillin Treatment Failure for Strep Throat
- Amoxicillin is equally effective as penicillin for the treatment of streptococcal pharyngitis and is often preferred due to its palatability 3.
- However, increased group A beta-hemolytic streptococcus (GABHS) treatment failure with penicillin has been reported, and amoxicillin may also be affected by this trend 3.
- The primary cause of penicillin treatment failure in streptococcal tonsillopharyngitis may be lack of compliance with the 10-day therapeutic regimen, but other causes such as reexposure to Streptococcus-infected family members or peers, copathogenicity, antibiotic-associated eradication of normal protective pharyngeal flora, and penicillin tolerance may also contribute to treatment failure 4.
- Cephalosporins have been demonstrated to be superior to penicillin at eradicating group A beta-hemolytic Streptococcus, and several are effective when administered for 4 to 5 days, which may be a preferable option in some cases 4.
- Guidelines recommend using clinical decision rules to assess the risk of group A beta-hemolytic streptococcal infection, followed by rapid antigen testing if a diagnosis is unclear, before prescribing antibiotics such as amoxicillin 5.
- Patients with worsening symptoms after appropriate antibiotic initiation or with symptoms lasting 5 days after the start of treatment should be reevaluated, as this may indicate treatment failure 5.
Causes of Treatment Failure
- Lack of compliance with the 10-day therapeutic regimen 4
- Reexposure to Streptococcus-infected family members or peers 4
- Copathogenicity, in which bacteria susceptible to a class of drugs are protected by other, colocalized bacterial strains that lack the same susceptibility 4
- Antibiotic-associated eradication of normal protective pharyngeal flora 4
- Penicillin tolerance, whereby streptococcal bacteria repeatedly or continuously exposed to sublethal concentrations of antibiotic become increasingly resistant to eradication 4