BIPHASIC ALLERGY TO ACETAMINOPHEN: AN ADDITIONAL APPEARANCE IN THE POST-DELIVERY POPULATION

Abstract

<h3>Introduction</h3> Acetaminophen is a widely used medicine with analgesic and antipyretic effects. Acetaminophen allergy is rare and biphasic reactions to it (within 72 hrs) are even less common. <h3>Case Description</h3> A 31 year-old female, with suspected allergy to acetaminophen presented with palmar pruritus, periorbital swelling and nasal congestion for allergy assessment. A drug provocation challenge (DPC) to acetaminophen was carried out for confirmation. An initial dose of 60 mg led to swelling of her lower lip and itching of her lips followed by right eyebrow swelling. Her blood pressure (BP) was stable at 119/82 mm[Hg]. She was confirmed as having an acetaminophen-induced allergic reaction and treated with rupatadine at 10 mg and recovered. That night, approximately 12 hours post-DPC, the patient awoke to feed her infant and experienced two consecutive syncopal episodes, followed by a rash and fever. There was no re-exposure to acetaminophen. Ambulance emergency services treated her with diphenhydramine and ER transport. There the patient was identified with a full-body rash and BP of 108/77 mm[Hg]. After a monitoring period of 4 hours, the patient was discharged home with a diagnosis of a biphasic allergic reaction to acetaminophen. <h3>Discussion</h3> This case illustrates a biphasic reaction to acetaminophen initially presenting post-delivery, a rare occurrence, in a patient previously tolerant to acetaminophen. In clinics choosing to test acetaminophen allergy, patients that fail oral challenge should be provided a care plan and education on how to treat any delayed reactions that may appear without allergen re-exposure.