Is there cross-reactivity between azithromycin (Zithromax) and erythromycin (Erythromycin) in patients with an erythromycin allergy?

From the Guidelines

There is no significant cross-reactivity between azithromycin and erythromycin allergy, and the risk of cross-reactivity is smaller than previously assumed. According to the Dutch Working Party on Antibiotic Policy (SWAB) guideline for the approach to suspected antibiotic allergy, published in 2023 in the journal Clinical Microbiology and Infection 1, the scientific data reviewed for this guideline strongly support a more liberal approach towards patients with a suspected antibiotic allergy. The guideline states that the risk of cross-reactivity is smaller than previously assumed, and that the time elapsed since the index reaction, and structured allergy anamnesis allows clinicians to assess the risk of recurrence of a (severe) allergic reaction.

Some key points to consider when evaluating the risk of cross-reactivity between azithromycin and erythromycin include:

• The patient's history of allergic reactions to erythromycin or other macrolide antibiotics
• The severity of the original allergic reaction
• The time elapsed since the index reaction
• The results of a structured allergy anamnesis

In general, patients with a suspected erythromycin allergy can be considered for treatment with azithromycin, but the decision should be made on a case-by-case basis, taking into account the individual patient's risk factors and medical history. It is essential to weigh the potential benefits of using azithromycin against the potential risks of an allergic reaction, and to consider alternative antibiotic options if necessary. As stated in the guideline, the implementation of the recommendations outlined may result in the use of smaller spectrum antibiotics with fewer side effects, less toxicity, and potentially lower risks of antibiotic resistance 1.

When deciding whether to use azithromycin in a patient with a suspected erythromycin allergy, clinicians should consider the following:

• The severity of the infection being treated
• The availability of alternative antibiotic options
• The patient's medical history and risk factors for allergic reactions
• The results of a structured allergy anamnesis and any other relevant diagnostic tests.

From the Research

Azithromycin Cross Reactivity with Erythromycin Allergy

• There is no direct evidence in the provided studies to suggest cross-reactivity between azithromycin and erythromycin allergy 2, 3, 4, 5, 6.
• Erythromycin is a macrolide antibiotic, and azithromycin is also a macrolide antibiotic, but the studies do not specifically address cross-reactivity between these two antibiotics 2.
• The studies discuss antibiotic allergy classification, cross-reactivity, and collaboration, but do not provide information on azithromycin and erythromycin cross-reactivity 3, 5.
• Penicillin allergy is discussed in several studies, but there is no mention of azithromycin or erythromycin cross-reactivity with penicillin allergy 3, 4, 6.
• The studies emphasize the importance of understanding antibiotic allergies and cross-reactivity to provide optimal patient care, but do not provide specific information on azithromycin and erythromycin cross-reactivity 4, 5, 6.