BMA Concise Guide to Medicine & Drugs


Brand name Tamiflu

Used in the following combined preparations None


Drug group Antiviral drug

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic No


Oseltamivir is an antiviral drug that is used to prevent or treat influenza (flu), a virus that infects and multiplies within the lungs. As well as regular seasonal flu, it is also effective against the avian (bird) flu and swine flu strains of the influenza virus. Oseltamivir works by blocking the entry of the virus into cells where they normally multiply before spreading throughout the body. This prevents or alleviates the typical symptoms of flu, which include sudden onset of fever, sweating and shivering, cough, runny or stuffy nose, headache, aching muscles, and extreme fatigue. The drug should be taken within 48 hours of the onset of these symptoms. It may reduce the duration of symptoms by 1–2 days.

Oseltamivir is not a substitute for seasonal flu vaccination and is not recommended for prevention of seasonal flu. However, because it does not alter the flu vaccine’s effectiveness, it can be taken even if you have been vaccinated.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Capsules, liquid (suspension).

Frequency and timing of doses Once daily (prevention); 2 x daily (treatment).

Dosage range Adults and adolescents over 13 years 75mg daily (prevention); 150mg daily (treatment). Children 1–13 years 30–75mg daily according to body weight (prevention); 60–150mg daily according to body weight (treatment).

Onset of effect Within 24 hours.

Duration of action 12–24 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug Do not stop taking the drug without consulting your doctor; symptoms may recur.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. However, if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.


The most common adverse effects – nausea, vomiting, and abdominal pain – mostly occur following the first dose and usually subside as treatment continues. Taking the drug with food helps to reduce these effects, but you should consult your doctor if they persist. If a rash occurs, you should stop taking the drug and contact your doctor. If psychosis or hallucinations occur, stop taking the drug and contact your doctor immediately.


None known.


Be sure to tell your doctor if:

· You have kidney problems.

· You have ever had an allergic reaction to oseltamivir.

· You are taking other medicines.

Pregnancy Safety in pregnancy not established. Discuss with your doctor.

Breast-feeding Safety in breast-feeding not established. Discuss with your doctor.

Infants and children No problems expected; not usually given under 1 year.

Over 60 No special problems.

Driving and hazardous work No known problems.

Alcohol No known problems.


No problems expected. The drug is not usually prescribed for longer than five days (children), seven days (adults), or six weeks (adults, during an epidemic).