What is a safe alternative to penicillin (Penicillin) for a patient with streptococcal pharyngitis taking Methotrexate (Methotrexate)?

From the Guidelines

For a patient with strep pharyngitis who is taking methotrexate and has a penicillin allergy, azithromycin is a safe alternative treatment option, with a recommended dosage of 12 mg/kg once daily (max = 500 mg) for 5 days, as supported by the Infectious Diseases Society of America guidelines 1. When prescribing for patients on methotrexate, it's essential to avoid antibiotics like trimethoprim-sulfamethoxazole (TMP-SMX) and other sulfonamides, as these can increase methotrexate levels and potentially cause toxicity by competing for protein binding and reducing renal clearance. Some key points to consider when selecting an antimicrobial for treatment of GAS pharyngitis include:

• Efficacy
• Safety
• Antimicrobial spectrum (narrow vs broad)
• Dosing schedule
• Compliance with therapy (i.e., adherence)
• Cost Macrolides like azithromycin generally don't significantly interact with methotrexate and don't affect its metabolism or excretion. Alternatively, clindamycin 7 mg/kg/dose 3 times daily (max = 300 mg/dose) for 10 days can be used, as it is considered safe and works through a different mechanism that doesn't interfere with methotrexate metabolism 1. The patient should complete the full course of antibiotics even if symptoms improve before completion to ensure complete eradication of the streptococcal infection. It's also important to note that first-generation cephalosporins, such as cefadroxil or cephalexin, can be used for patients allergic to penicillin who do not manifest immediate-type hypersensitivity to β-lactam antibiotics, but they should be avoided in individuals with immediate type hypersensitivity to penicillin 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 Azithromycin is often effective in the eradication of susceptible strains of Streptococcus pyogenes from the nasopharynx 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

Azithromycin is a safe alternative for penicillin for a patient with strep pharyngitis, including those taking methotrexate, as it is effective in the eradication of susceptible strains of Streptococcus pyogenes from the nasopharynx.

• The patient should be tested for susceptibility to azithromycin before treatment.
• Azithromycin should only be used to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. 2 2

From the Research

Safe Alternatives to Penicillin for Strep Pharyngitis

For a patient with strep pharyngitis taking methotrexate, it is crucial to find a safe alternative to penicillin due to potential drug interactions.

• First-generation cephalosporins are recommended for patients with nonanaphylactic allergies to penicillin 3, 4, 5.
• Macrolides, such as azithromycin, can be considered, but their effectiveness may vary, and resistance has been reported in some areas 4, 6.
• Clindamycin is another option for patients allergic to penicillin 5.
• Carbacephem may provide better symptom resolution compared to penicillin, but more research is needed to confirm its effectiveness 6.

Considerations for Patients Taking Methotrexate

When prescribing antibiotics to patients taking methotrexate, it is essential to consider potential drug interactions and adjust the treatment plan accordingly.

• Methotrexate can increase the risk of adverse effects when combined with certain antibiotics, such as trimethoprim-sulfamethoxazole 7.
• The choice of antibiotic should be based on the patient's medical history, allergy status, and potential drug interactions.

Antibiotic Treatment Guidelines

The American family physician recommends the following guidelines for antibiotic treatment of strep pharyngitis:

• Penicillin or amoxicillin for 10 days is the first-line treatment 3, 4, 5.
• First-generation cephalosporins are recommended for patients with nonanaphylactic allergies to penicillin 3, 4, 5.
• Macrolides, such as azithromycin, can be considered for patients with penicillin allergy, but their effectiveness may vary 4, 6.