Oseltamivir-Associated Angioedema in a Patient Receiving Angiotensin-Converting Enzyme Inhibitor Therapy for Influenza A: A Case Report.

Influenza remains a major cause of morbidity and mortality worldwide, particularly among elderly patients with comorbidities. Oseltamivir (Tamiflu), a neuraminidase inhibitor, is the most widely prescribed antiviral therapy for influenza A and B. Although oseltamivir is associated with increased nausea and vomiting, it is generally well tolerated. On rare occasions, oseltamivir has been associated with rare hypersensitivity reactions, including angioedema. Angiotensin-converting enzyme (ACE) inhibitors are also well known to cause angioedema, sometimes years after therapy initiation. We present the case of a 73-year-old man with influenza A who developed acute lip swelling after starting oseltamivir while on long-term lisinopril therapy. Oseltamivir was discontinued, and the swelling subsided. This raised important diagnostic and therapeutic considerations in differentiating viral illness, drug reaction, and medication-induced angioedema.