Incidence of fidaxomicin allergy in patients with macrolide allergies: a large database analysis

Area of Science:

• Pharmacology
• Allergy and Immunology
• Infectious Diseases

Background:

• Fidaxomicin is a macrocyclic antibiotic used for Clostridioides difficile infection.
• Macrolide antibiotics share a common chemical structure, raising concerns about cross-reactivity.
• Previous data on fidaxomicin cross-reactivity in patients with existing macrolide allergies is limited.

Purpose of the Study:

• To investigate the association between prior macrolide allergies and the risk of fidaxomicin allergy.
• To quantify the odds and absolute risk of fidaxomicin allergy in patients with allergies to specific macrolides (azithromycin, clarithromycin, erythromycin).
• To assess the temporal relationship between non-fidaxomicin macrolide allergy and severe allergic reactions to fidaxomicin.

Main Methods:

• Retrospective analysis of patient data.
• Comparison of fidaxomicin allergy rates between patients with and without prior macrolide allergies.
• Calculation of odds ratios and absolute risk for fidaxomicin allergy based on specific macrolide allergies.

Main Results:

• Patients with azithromycin, clarithromycin, and erythromycin allergies had significantly higher odds of fidaxomicin allergy (ORs 2.31, 8.37, 1.58, respectively).
• Absolute risks of fidaxomicin allergy were 0.033, 0.01, and 0.039 for patients with prior azithromycin, clarithromycin, and erythromycin allergies, respectively.
• Anaphylaxis and angioedema risks were elevated within one year following a non-fidaxomicin macrolide allergy.

Conclusions:

• Fidaxomicin may exhibit cross-reactivity in patients with a history of macrolide allergies.
• Clinicians should exercise caution when prescribing fidaxomicin to patients with known allergies to azithromycin, clarithromycin, or erythromycin.
• Further research may be warranted to elucidate the precise mechanisms of cross-reactivity and refine risk assessment strategies.