Potential cross-reactivity of polysorbate 80 and cremophor: A case report.

INTRODUCTION: Anaphylactic and hypersensitivity reactions are known adverse effects of many drug products and may be due to the inactive ingredients of the drug formulation. Specifically for paclitaxel and docetaxel, it is their excipients (cremophor and polysorbate 80, respectively) that have been identified as being most likely responsible for these reactions. CASE REPORT: The patient is a 39-year-old female, with a history of breast cancer and no known allergies, who was scheduled to start chemotherapy. While being administered fosaprepitant, she reported shortness of breath and was noted to be hypotensive and flushed. Two months later, the patient returned to clinic to start weekly paclitaxel. During the administration of the paclitxel test dose, the patient reported difficulty breathing, flushing, and chest tightness. Management and outcome: Both medication reactions were managed with epinephrine and other supportive medications. Fosaprepitant was taken out of the patient's antiemetic regimen for future cycles and paclitaxel was switched to nab-paclitaxel. DISCUSSION: It is well documented that paclitaxel and fosaprepitant have the potential to cause hypersensitivity reactions due to their excipients. While it is likely that each reaction was a unique event, it is difficult to ignore the possibility of cross-reactivity due to the presence of oleic acid in both excipients.