Potential Anaphylaxis to Systemic Phenylephrine: A Case Report

This case summarizes a 66 year old woman with a past medical history of asthma, breast cancer, anxiety, and chronic back pain with prior surgical insertion of spinal hardware, presenting for removal of spinal hardware at L5-S1 and spinal laminectomy and fusion at L4-L5. Her course was complicated by acute blood loss anemia and post-operative hypotension managed with a phenylephrine infusion, for which she experienced a possible anaphylactic reaction requiring upgrade to the intensive care unit. She was managed using intramuscular epinephrine, diphenhydramine, methylprednisolone, albuterol, famotidine, and oxygen. As phenylephrine is structurally similar to the endogenous catecholamines epinephrine and norepinephrine, diagnosis of her reaction was difficult. However, phenylephrine contains sodium metabisulfite, a preservative sulfite that may cause allergic-type reactions, particularly in patients with asthma in their medical history. Her hypersensitivity reaction was likely secondary to her use of phenylephrine, and she was discharged with a plan for outpatient follow up with the allergy team. As this case exemplifies, patients with a predisposition to allergic reactions should be closely monitored for possible hypersensitivity to preservatives and excipients in medications.