Abstract
Oseltamivir is widely used as the first-line therapy for influenza, and is generally well tolerated but has been associated with rare neuropsychiatric adverse events (NPAEs). These reactions range from mild confusion to severe delirium and abnormal behaviour, often occurring within 48 hours of treatment initiation. We report a case of probable oseltamivir-induced neuropsychiatric toxicity in an elderly patient with multiple comorbidities. A 74-year-old man with chronic kidney disease and ischemic heart disease presented with breathing difficulty and was admitted to the intensive care unit for hypoxic respiratory failure. Empirical therapy with renally adjusted oseltamivir (75 mg once daily) was initiated on Day 3 of admission for suspected viral pneumonia. On Day 5, the patient developed acute hyperactive delirium and severe restlessness requiring physical restraints. Oseltamivir was discontinued on Day 9, after which the patient’s neuropsychiatric symptoms completely resolved by Day 11. The close temporal association between drug exposure and symptom onset, along with prompt resolution after withdrawal, supports a probable causal relationship. This case underscores the need for heightened vigilance when prescribing oseltamivir to high-risk populations, particularly elderly patients with renal impairment, and highlights the importance of early recognition and prompt discontinuation to prevent morbidity.

Key words: Oseltamivir, Neuropsychiatric toxicity