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Pharm 101: Oseltamivir

Class

Anti-influenza agent

Other examples: zanamivir, amantadine

Pharmacodynamics
  • Oseltamivir and zanamavir are neuraminidase (a glycoprotein) inhibitors
  • Disrupt viral replication and release
  • Active against both influenza A and B
Pharmacokinetics
  • 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
Precautions/contraindications
  • Dose adjustment in renal insufficiency
References

Pharmacology 101

Top 200 drugs

Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Co-creator of the LITFL ECG Library. Twitter: @rob_buttner

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