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

Pharm 101 700

Pharmacology 101

Top 200 drugs

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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