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Brand Names: Tamiflu
Generic Name: Oseltamivir
How does Tamiflu 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.
Flu is caused by a highly contagious virus that affects the lungs and airways (respiratory system). The virus is caught by inhaling microscopic airbourne droplets that are produced when an infected person talks, coughs or sneezes. The virus can also survive for a short-time on surfaces, so can be picked up if a person touches an infected surface and then rubs their nose or eyes. When the virus enters the body it invades cells in the airways, where it replicates to form lots of new copies of the virus.
The new copies of the virus leave the first cells and move on to infect adjoining cells, where the process is repeated. After a couple of days enough cells have been infected that the patient feels flu symptoms such as headache, fever and general aches and pains. These continue for about a week until the body's immune system kills the virus.
In order to leave one cell and infect another, the influenza virus uses a chemical helper that is found on its surface. This substance is an enzyme called neuraminidase. Without it, newly formed copies of the virus can't leave the infected cells to infect other cells.
Oseltamivir works by binding to the neuraminidase on the surface of the virus and stopping it from working. This prevents the flu virus from spreading and infecting other cells and so 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.
In people who are otherwise healthy, oseltamivir has been shown to reduce the duration of flu symptoms 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. To treat the flu the medicine should be started within 48 hours of the symptoms starting.
Oseltamivir can also be used to prevent flu in people who have been in contact with someone with the virus. The medicine should be started within 48 hours of being in contact with the infected person.
What is Tamiflu used for?
• Treatment of flu (influenza) in adults and children over one year of age, when the influenza virus is circulating in the community.
• Prevention of flu (influenza) 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 (influenza) 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.
The National Institute of Clinical Excellence (NICE) has recommended that oseltamivir should not be prescribed to treat or prevent flu in people 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 lung disease, eg asthma or COPD, long-term kidney, liver, heart or neurological disease, diabetes, or a poorly functioning immune system. In addition, NICE recommend oseltamivir should only be used in these people if the influenza virus is known to be going around in significant amounts.
To treat flu, people must be able to start treatment within 48 hours of the symptoms starting. To prevent flu, people must be living in close contact with someone who has symptoms of flu, and must be able to start treatment within 48 hours of being exposed to that person. They must also be not effectively protected by flu vaccination.
• 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 this 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 diabetes or chronic heart or lung disease and people with a weakened immune system.
• 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.
• 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, preferably by returning to your pharmacy.
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 effectiveness of this medicine in children under one year of age has not been established.
• Tamiflu suspension contains sorbitol and may not be suitable for people with a hereditary intolerance to fructose. Tamiflu capsules do not contain sorbitol.
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.
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.
• Feeling sick (nausea) or vomiting.
• Abdominal pain.
• Difficulty sleeping (insomnia).
• Sensation of spinning (vertigo).
• Skin rash, eczema or hives.
• Liver inflammation (hepatitis).
• Severe skin reactions.
Convulsions (fits) and psychiatric events, such as decreased conciousness, abnormal behaviour, hallucinations and delirium have also been reported in people taking this medicine to treat flu. These symptoms were mainly reported in children and adolescents. However, these symptoms have also been reported in people with flu who were not taking this medicine, so the association with this medicine is not clear. If you or your child experience any of these symptoms while taking this medicine you should consult your doctor immediately.
The side effects listed above may not include all of the side effects reported by the medicine'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.
How can this medicine affect other medicines?
It is unlikely that this medicine will affect other medicines. However you should tell your doctor or pharmacist what medicines you are using, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Likewise, check with your doctor or pharmacist before starting any new medicines while you are using this medicine, so they can check that the combination is safe.
The manufacturer of this medicine states that it should be used with caution in people who are taking the following medicines, as oseltamivir may possibly reduce the removal of these medicines from the body by the kidneys: