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
- Katzung BG. Basic and Clinical Pharmacology. 14e. 2018: 891-892
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