What is the appropriate treatment for streptococcal (strep) pharyngitis in a patient with a penicillin allergy?

From the Guidelines

For patients with strep pharyngitis who have a penicillin allergy, the recommended first-line treatment is azithromycin 12 mg/kg once daily (max = 500 mg) for 5 days, as it is a strong and moderate recommendation according to the Infectious Diseases Society of America guidelines 1.

Treatment Options

• Azithromycin 12 mg/kg once daily (max = 500 mg) for 5 days is a suitable option for patients with penicillin allergy, as it has a strong and moderate recommendation 1.
• Clarithromycin 7.5 mg/kg/dose twice daily (max = 250 mg/dose) for 10 days or clindamycin 7 mg/kg/dose 3 times daily (max = 300 mg/dose) for 10 days can be used as alternative treatments, as they also have strong and moderate recommendations 1.
• For patients with non-severe penicillin allergies, cephalosporins like cefdinir or cephalexin may be considered, as cross-reactivity is low (around 1-10%) 1.

Importance of Completing Antibiotic Course

When prescribing, it's essential to complete the full course of antibiotics even if symptoms improve to prevent complications like rheumatic fever or post-streptococcal glomerulonephritis 1.

Additional Recommendations

• Patients should be advised to rest, maintain hydration, use throat lozenges or warm salt water gargles for symptom relief, and take acetaminophen or ibuprofen for pain and fever.
• These macrolide antibiotics work by inhibiting bacterial protein synthesis, though they have slightly lower efficacy rates compared to penicillin.
• Patients can generally return to work or school after 24 hours of antibiotic therapy when they are no longer contagious.

From the FDA Drug Label

Pharyngitis/tonsillitis caused by Streptococcus pyogenes as an alternative to first-line therapy in individuals who cannot use first-line therapy NOTE: Penicillin by the intramuscular route is the usual drug of choice in the treatment of Streptococcus pyogenes infection and the prophylaxis of rheumatic fever. Azithromycin is often effective in the eradication of susceptible strains of Streptococcus pyogenes from the nasopharynx Because some strains are resistant to azithromycin, susceptibility tests should be performed when patients are treated with azithromycin. Data establishing efficacy of azithromycin in subsequent prevention of rheumatic fever are not available.

Azithromycin can be used as an alternative to first-line therapy for the treatment of Streptococcus pyogenes (strep pharyngitis) in individuals who cannot use first-line therapy, such as those with a penicillin allergy.

• The clinical success rate (i.e., cure and improvement) of azithromycin in the treatment of pharyngitis due to documented Group A β-hemolytic streptococci (GABHS or S. pyogenes) was 98% at Day 14 and 94% at Day 30.
• However, susceptibility tests should be performed to ensure the effectiveness of azithromycin, as some strains of Streptococcus pyogenes may be resistant to the medication.
• Additionally, data establishing efficacy of azithromycin in subsequent prevention of rheumatic fever are not available 2.

From the Research

Treatment Options for Strep Pharyngitis in Patients with Penicillin Allergy

• Erythromycin and first-generation cephalosporins are options for patients with penicillin allergy, as stated in the study 3.
• The study 4 compared different antibiotics, including cephalosporins and macrolides, with penicillin, but found low-certainty evidence and uncertain results regarding symptom resolution and clinical relapse.
• Azithromycin was compared to amoxicillin in one trial, with uncertain results regarding symptom resolution and relapse, but with more adverse events reported with azithromycin 4.
• Carbacephem may be more effective than penicillin for symptom resolution, according to low-certainty evidence in the study 4.

Diagnostic Methods and Clinical Guidelines

• The diagnosis of GABHS pharyngitis can be complicated by overlapping symptoms with non-GABHS and viral causes, as mentioned in the study 5.
• Clinical scoring systems, rapid antigen detection tests, throat culture, nucleic acid amplification tests, and machine learning and artificial intelligence can be used to diagnose GABHS, as discussed in the study 5.
• Clinical guidelines for diagnosing GABHS vary significantly between professional associations, and most physicians do not follow published guidelines, according to the study 5.

Antibiotic Treatment and Efficacy

• Antibiotics with narrow spectrums of activity are considered appropriate for treating strep throat, as stated in the study 5.
• A 3-day azithromycin regimen was compared to a 10-day penicillin V regimen in children with acute GAS pharyngitis, with similar clinical efficacy but lower bacteriologic eradication with azithromycin, as reported in the study 6.
• The study 3 recommends penicillin as the treatment of choice for strep pharyngitis due to its cost, narrow spectrum of activity, and effectiveness, but notes that amoxicillin is equally effective and more palatable.