Product Summary
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 neighbouring 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 it used for?
- Treating flu (influenza) in adults and children over one year of age, when the influenza virus is circulating in the community.
- Treating flu (influenza) in children aged 6 to 12 months during a pandemic outbreak of flu.
- Preventing flu (influenza) in adults and children over one year of age who live in close contact with someone who has been diagnosed with flu, when the influenza virus is circulating in the community.
- Preventing 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.
Tamiflu is being used to treat people infected with swine flu during the current pandemic. Swine flu is caused by a strain of the influenza type A virus known as H1N1.
To treat flu (including swine flu), people must be able to start treatment with Tamiflu within 48 hours of the symptoms starting. To prevent flu, people must be able to start treatment within 48 hours of being exposed to the household contact who has the flu. During the current swine flu pandemic, doctors will usually only prescribe Tamiflu to prevent flu in people who fall into one of the higher-risk groups and are living with someone who has been diagnosed with swine flu.
In non-pandemic circumstances the National Institute of Clinical Excellence (NICE) recommends that oseltamivir should not be prescribed to treat or prevent normal seasonal 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.
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