Oseltamivir – Neuraminidase inhibitor for influenza treatment and prevention.
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What is Oseltamivir?
Oseltamivir (Tamiflu) is an important antiviral medication for influenza that can reduce the duration and severity of flu symptoms when used appropriately. It’s particularly valuable for high-risk patients and during flu outbreaks for both treatment and prevention.
Book an online consultation if you’ve been exposed to confirmed influenza, are experiencing flu-like symptoms, or are at high risk during flu season and need assessment for antiviral treatment or prevention. Our GPs can evaluate your symptoms and risk factors to determine if Oseltamivir is appropriate for your situation.
What is Oseltamivir used for?
- Treatment of influenza A and B
- Prevention of influenza in high-risk individuals
- Post-exposure prophylaxis for influenza
- Treatment in immunocompromised patients
- Pandemic influenza preparedness
- Severe influenza requiring hospitalization
How does Oseltamivir work?
A neuraminidase inhibitor that blocks the enzyme influenza viruses need to release newly formed viral particles from infected cells, preventing the spread of infection within the body.
Dosage and Administration
Adults
Treatment: 75mg twice daily for 5 days. Prevention: 75mg once daily for 10 days (or longer during outbreaks).
Children
Weight-based dosing: 30-75mg depending on weight—specialist supervision for under 1 year.
Important Notes
- Start within 48 hours of symptom onset for treatment.
- Take with food to reduce nausea.
- Complete the full course even if symptoms improve.
- For prevention, start within 48 hours of exposure.
Side Effects
Common Side Effects
- Nausea and vomiting
- Headache
- Fatigue
- Dizziness
- Insomnia
- Cough
- Diarrhoea
Serious Side Effects
Seek immediate medical attention if you experience:
- Severe allergic reactions
- Psychiatric effects (confusion, abnormal behavior)
- Skin reactions (rare)
- Worsening of underlying conditions
Important Warnings
- Must start within 48 hours of symptom onset to be effective for treatment.
- Monitor for unusual behavior or mood changes, especially in children and adolescents.
- Tell your GP if you have kidney problems—dose adjustment may be needed.
- Not effective against bacterial infections or common cold.
- Limited benefit if started more than 48 hours after symptom onset.
Drug Interactions
Tell your GP if you're taking any of the following medications:
- Live influenza vaccine—avoid vaccine within 48 hours before to 2 weeks after oseltamivir.
- Probenecid—may increase oseltamivir levels.
- Generally few significant drug interactions.
- Safe to use with most other medications.
Frequently Asked Questions
How effective is Oseltamivir for treating flu?
When started within 48 hours, it can reduce flu symptoms by about 1-2 days and reduce severity, but it doesn't cure flu—it just shortens the course.
Should I take Oseltamivir to prevent flu?
It's typically only recommended for prevention in high-risk individuals during outbreaks or after close contact with confirmed flu cases.
Can I give Oseltamivir to my child?
Yes, it can be used in children from 1 year of age, with doses calculated based on weight. Liquid formulations are available for younger children.
Will Oseltamivir work if I've had flu symptoms for 3 days?
It's much less effective if started more than 48 hours after symptom onset, but may still be prescribed for severe cases or high-risk patients.
Medically Reviewed by: Mohammed Hassan - Independent Prescriber
Last Updated: 2025-01-14