Relenza

How does it work?

Relenza inhalation powder contains the active ingredient zanamivir, which is a type of medicine called a neuraminidase inhibitor. It is used to treat and prevent infection with the influenza virus (flu).

Flu is caused by a highly contagious virus that affects the respiratory system (lungs and airways). 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.

These 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.

Zanamivir 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, zanamivir has been shown to reduce the duration of flu symptoms by approximately one to one and a half days. To treat the flu in adults, the medicine should be started within 48 hours of the symptoms starting. In children it should be started within 36 hours of the symptoms starting.

Zanamivir can also be used to prevent flu in people who have been in contact with someone with the virus. In this case the medicine should be started within 36 hours of being in contact with the infected person.

The National Institute of Clinical Excellence (NICE) has recommended that zanamavir should not be prescribed to people who have flu but are otherwise healthy. They recommend that it is only used to treat 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, significant heart disease, long-term kidney disease, diabetes, or a poorly functioning immune system. In addition, they recommend 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 (influenza type A or B) in adults and children aged five years and over, when the influenza virus is circulating in the community.

Prevention of flu (influenza type A or B) in adults and children aged five years and over, who have been in contact with someone in their household who has been diagnosed with flu.

Prevention of flu (influenza type A or B) in adults and children aged five years and over, 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!

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.

Follow the printed instructions you have been given with this medicine. The powder in the Relenza blisters is to be inhaled using the diskhaler provided. The blisters should not be taken by mouth.

If you have asthma or COPD and use a regular bronchodilator inhaler (a reliever that opens your airways, eg salbutamol or terbutaline), you should it before inhaling your dose of Relenza.

This medicine may very rarely cause the airways to narrow after it has been inhaled, making breathing difficult. If this happens, you should stop using this medicine immediately and seek medical advice. If you suffer from asthma or chronic obstructive airways disease (eg bronchitis or emphysema) you should have your reliever inhaler (eg salbutamol or terbutaline) at hand when you are taking this medicine, so that you can use it to relieve shortness of breath in the rare event that this side effect occurs.

At the moment it is not known how effective this medicine will be at treating flu in people with 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 how effective it will be in people with severe asthma, chronic lung disease, or other unstable long-term illnesses, or in people aged over 65 years. It is not known how effective this medicine will be for preventing outbreaks of flu in nursing homes.

Use with caution in

Asthma

Chronic obstructive pulmonary disease

Not to be used in

Known sensitivity or allergy to any ingredient.

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 expected benefit to the mother is thought to outweigh any possible risk to the developing baby. Seek medical advice from your doctor.

It is not known if this medicine passes into breast milk. It is not recommended for women who are breastfeeding. 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. Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

Narrowing of the airways (bronchospasm)

Difficulty in breathing (dyspnoea)

Throat tightness

Rash

Allergic reaction with swelling of the face or throat

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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