What is the treatment for streptococcal (strep) infection in a patient allergic to penicillin (PCN)?

From the Guidelines

For patients with strep throat who are allergic to penicillin, the most effective alternative antibiotic treatment is azithromycin (12 mg/kg once daily, max 500 mg, for 5 days) or clarithromycin (7.5 mg/kg/dose twice daily, max 250 mg/dose, for 10 days), as recommended by the Infectious Diseases Society of America 1. When considering treatment options for streptococcal infections in patients allergic to penicillin, it's crucial to prioritize alternatives that are effective against Streptococcus pyogenes while minimizing the risk of adverse reactions.

• The choice between azithromycin and clarithromycin may depend on factors such as the severity of the allergy, the patient's age, and potential drug interactions.
• Cephalosporins like cephalexin (20 mg/kg/dose twice daily, max 500 mg/dose, for 10 days) can be considered for patients with non-severe penicillin allergies, but caution is advised due to the risk of cross-reactivity 1.
• Clindamycin (7 mg/kg/dose three times daily, max 300 mg/dose, for 10 days) is another option, particularly for patients with severe penicillin allergies, although its use may be limited by resistance patterns and potential side effects.
• It is essential to complete the full course of antibiotics, even if symptoms improve before finishing treatment, to ensure eradication of the organism and prevent complications such as acute rheumatic fever.
• Symptomatic relief can be achieved with over-the-counter pain relievers like acetaminophen or ibuprofen, salt water gargles, and plenty of fluids.
• If the penicillin allergy is uncertain, allergy testing may be beneficial, as penicillins are generally the most effective treatment for strep infections 1.

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 Respiratory tract infections caused by Streptococcus pneumoniae and Streptococcus pyogenes (Penicillin is the usual drug of choice in the treatment and prevention of streptococcal infections, including the prophylaxis of rheumatic fever

The treatment for streptococcal (strep) infection in a patient allergic to penicillin (PCN) is azithromycin or cephalexin as an alternative to first-line therapy.

• Azithromycin is often effective in the eradication of susceptible strains of Streptococcus pyogenes from the nasopharynx 2.
• Cephalexin is generally effective in the eradication of streptococci from the nasopharynx 3. Susceptibility tests should be performed when patients are treated with these antibiotics to ensure effectiveness 2 2.

From the Research

Treatment Options for Strep Infection in Penicillin-Allergic Patients

• For patients allergic to penicillin, alternative treatments for streptococcal pharyngitis include 10-day courses of 1st-generation oral cephalosporins or erythromycin 4
• Macrolides such as clarithromycin and azithromycin are also suitable alternatives, offering lower rates of gastrointestinal complaints and more convenient dosing 5
• Azithromycin can be administered for 5 days, compared to 10 days for penicillin, erythromycin, and clarithromycin 5
• However, a study found that 10 days of clarithromycin therapy was more effective than 5 days of azithromycin therapy in eradicating group A streptococci 6

Safety of Alternative Antibiotics

• Azithromycin has been shown to be safe in patients allergic to penicillin and/or cephalosporin, with no reactions observed in a study of 48 patients 7
• Clinicians should consider antimicrobial therapy with an antibiotic that does not cross-react with penicillins or beta-lactams when treating penicillin-allergic patients 8

Antibiotic Selection

• The choice of antibiotic for penicillin-allergic patients depends on the type of allergic reaction, with beta-lactam antibiotics suitable for patients with unknown or possible reactions, and non-beta-lactam antibiotics recommended for patients with hives or anaphylactic reactions 8