Oseltamivir
1 medicine
Oseltamivir is an antiviral used to treat and prevent influenza. It works best when started within 48 hours of symptoms starting, and has been linked to confusion or unusual behaviour, reported more often in children.
Key facts
- Oseltamivir (sold as Tamiflu and generics) is an antiviral that treats influenza A and B, and can also be taken to help prevent flu after close contact with someone infected.
- For treatment, it works best when started within 48 hours of symptoms starting; started later it still has some effect but is less useful.
- Oseltamivir has been linked to confusion, abnormal behaviour, or hallucinations, reported more often in children and teenagers; watch closely for any unusual behaviour during treatment.
- Seek urgent care for difficulty breathing, chest pain, or sudden confusion, unusual behaviour, or self-harm risk.
What oseltamivir treats
Oseltamivir treats influenza (flu) caused by influenza A and B viruses in people who have had symptoms for no more than 1 to 2 days. It is also used to prevent flu in people who have been exposed to someone infected, or during a local outbreak. It does not treat the common cold or other respiratory infections, and it is not a substitute for annual flu vaccination.
How oseltamivir works
Oseltamivir is a prodrug: after you swallow it, the liver converts it to its active form, oseltamivir carboxylate. This active form blocks neuraminidase, an enzyme on the surface of influenza virus particles that the virus needs to break free from an infected cell and spread to new ones. By blocking neuraminidase, oseltamivir slows the spread of infection within the body, reducing the severity and length of illness.
Before you take it
- Tell your prescriber about any kidney problems, since the dose is lower if kidney function is reduced.
- Tell your prescriber if you or your child has a history of mental health problems or unusual reactions to medicines.
- Take it with food if it upsets your stomach; this does not reduce how well it works.
- If you are pregnant or breastfeeding, discuss the risks and benefits with your prescriber.
Side effects
Common effects are nausea and vomiting, usually mild and reduced by taking the dose with food.
Stop and seek urgent medical care for any of these:
- Sudden confusion, unusual behaviour, hallucinations, or delirium, particularly in children.
- Signs of a severe allergic reaction: swelling of the face or throat, or difficulty breathing.
- A severe skin reaction with blistering or peeling.
- Worsening breathlessness, chest pain, or a high fever that does not settle.
Safety essentials
- Oseltamivir works best started within 48 hours of flu symptoms beginning, and anyone taking it, especially a child, should be watched closely for confusion or unusual behaviour; these are the two facts to keep in mind before and during treatment.
- Report any sudden change in behaviour or alertness immediately, particularly in children and teenagers, even though a clear causal link to the drug has not been firmly established.
- Complete the full course as prescribed, and keep taking sensible precautions (hand hygiene, staying away from others while infectious) since oseltamivir reduces symptoms but does not eliminate the risk of spreading flu to others.
This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.