Tamiflu (oseltamivir)

How does it work?

Tamiflu capsules and suspension contain the active ingredient oseltamivir phosphate, which is a type of medicine called a neuraminidase inhibitor. It is used to treat and prevent infection with the influenza (flu) virus.

Influenza is caused by a highly contagious virus that affects the respiratory system. The virus is passed from one person to another by coughing and sneezing. When the virus enters the body it invades cells, where it replicates to form lots of new virus particles.

These new copies of the virus are released from the cells and then move on to infect adjoining cells, where the process is repeated. After a couple of days a sufficient number of cells have been infected so that the patient feels flu symptoms such as headache, fever and general aches and pains, which continue for about a week until the body's immune system kills the virus.

In order to leave one cell and infect another, the flu virus uses a chemical helper that is found on its surface. This substance is an enzyme called neuraminidase and without it, the newly formed virus particles cannot leave the infected cells.

Oseltamivir works by binding to the neuraminidase on the surface of the virus particles and stopping it from working. When the neuraminidase helper is blocked in this way, it means that newly formed viral particles cannot be released from the infected cells. This prevents the flu virus from spreading and infecting other cells.

Oseltamivir therefore confines the infection to a smaller area. This makes the symptoms of the infection less severe and also makes it is easier for the body's immune system to kill the virus. The medicine has been shown to reduce the duration of the illness by approximately one to one and a half days and to reduce the risk of developing flu-related complications, such as chest infections that require antibiotics. It is used to treat flu and can also be used to prevent flu in people who have been in contact with someone with the virus.

This medicine is only effective against the influenza virus. It will not work against illnesses that are caused by other agents.

At the moment it is not known if this medicine will be effective at treating or preventing flu if you have a weakened immune system, for example due to HIV infection or treatment with immunosuppressant medicines such as chemotherapy or corticosteroids. It is also not known if it will be effective for treating flu in people with chronic heart or lung disease, or in people with medical conditions that are sufficiently severe or unstable to potentially require admission to hospital.

The National Institute of Clinical Excellence (NICE) has recommended that oseltamivir should not be prescribed to people who have flu but who are otherwise healthy. They recommend that it is only prescribed to people who are at risk of developing complications from flu. These people are those aged over 65 years and those with chronic respiratory disease, eg asthma or COPD, significant heart disease, long-term kidney disease, diabetes, or a poorly functioning immune system. In addition, it should only be used in these people if they can start treatment within two days of the onset of symptoms and if the influenza virus is known to be circulating in the community.

What is it used for?

Treatment of flu in adults and children over one year of age, when the influenza virus is circulating in the community.

Prevention of flu in adults and children over one year of age, who have been in contact with someone diagnosed with flu when it is circulating in the community.

Prevention of flu in adults and children over one year of age in exceptional circumstances, such as during a pandemic, or in cases when flu vaccination doesn't provide protection against the strain of flu virus that is circulating.

Warning!

Take this medicine at regular intervals as prescribed. Complete the prescribed course unless otherwise directed by your doctor.

This medicine should not be used as a substitute for being vaccinated against flu, because the protection against flu lasts only as long as you take the medicine. People who are at risk of complications if they contract flu should continue to have a yearly flu-vaccination to prevent the illness. These people include the elderly, people with chronic heart or lung disease, and people with a weakened immune system.

Tamiflu suspension contains sorbitol and may not be suitable for people with a hereditary intolerance to fructose. Tamiflu capsules do not contain sorbitol.

Once reconstituted (your pharmacist will normally do this), Tamiflu suspension should be stored in a fridge at 2-8°C and not used for longer than ten days. Shake the bottle before giving a dose. Any suspension that remains after ten days should be carefully disposed of.

Use with caution in

Decreased kidney function.

Not to be used in

Allergy to any ingredient.

This medicine is not recommended for people with severely decreased kidney function or kidney failure.

The safety and efficacy of this medicine in children under one year of age has not been established.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy. If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

The safety of this medicine for use during pregnancy has not been established. It is not recommended for use in pregnancy unless the potential benefit to the mother outweighs any potential risk to the developing foetus. Seek medical advice from your doctor.

It is not known if this medicine passes into breast milk. It is not recommended for use during breastfeeding unless unless the potential benefit to the mother outweighs any potential risk to the nursing infant. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Nausea.

Vomiting.

Abdominal pain.

Diarrhoea.

Indigestion.

Headache.

Tiredness.

Dizziness.

Difficulty sleeping (insomnia).

Conjunctivitis.

Nosebleeds.

Rash.

Liver inflammation (hepatitis).

Severe skin reactions.

The side effects listed above may not include all of the side effects reported by the drug's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

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