Pharm 101: Oseltamivir


Anti-influenza agent

Other examples: zanamivir, amantadine

  • Oseltamivir and zanamavir are neuraminidase (a glycoprotein) inhibitors
  • Disrupt viral replication and release
  • Active against both influenza A and B

  • PO administration
  • Activated by hepatic esterases and widely distributed
  • Bioavailability 80%
  • Low plasma protein binding
  • Half-life 6-10 hours
  • Renal excretion by glomerular filtration and tubular secretion

Clinical uses
  • Treatment of uncomplicated influenza
    • 5 day course of therapy (75 mg BD) within 48 hours of symptom onset shortens severity and duration of illness
    • May decrease incidence of respiratory complications
  • Higher risk groups e.g. indigenous, elderly, pregnant women, immunocompromised
    • Primary prevention by vaccination is preferred
    • Used preferably at early phase of pandemic to limit spread and numbers infected, and limit severity of disease in those infected
  • Once daily prophylaxis is 70-90% effective in preventing disease after exposure

Adverse effects
  • Nausea/vomiting
  • Headache
  • Fatigue and diarrhoea (more common with prophylactic use)
  • Neuropsychiatric events (self-injury and delirium) have been reported

  • Dose adjustment in renal insufficiency


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MBBS (UWA) CCPU Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

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