Zanamivir (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 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.

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.

Relenza inhalation powder comes packed in blisters on circular foil disks that are used in a type of inhalation device called a diskhaler. The diskhaler pierces the blister when it is used and the powder is then inhaled through the mouthpiece. This deposits the medicine in the throat, airways and lungs, where it can attack the virus. Follow the instructions provided with the diskhaler and ask your doctor or pharmacist for advice if you have any problems.

What is it used for?

  • Treating flu (influenza type A or B) in adults and children aged five years and over, when the influenza virus is circulating in the community.
  • Preventing flu (influenza type A or B) in adults and children aged five years and over who live in close contact with someone who has been diagnosed with flu.
  • Preventing 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.

Relenza is being used to treat certain people (including pregnant women and people with severe kidney disease) infected with swine flu during the current pandemic. Swine flu is caused by a strain of the influenza type A virus known as H1N1. Click here for everything you need to know about swine flu.

To treat flu, adults must be able to start treatment within 48 hours of the symptoms starting. Children should start treatment within 36 hours of the symptoms starting. To prevent flu, adults and children must be able to start treatment within 36 hours of being exposed to the household contact who has the flu. During the current swine flu pandemic, doctors will usually only prescribe Relenza 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 zanamivir 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 zanamivir should only be used in these people if the influenza virus is known to be going around in significant amounts.

Warning!

  • 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.
  • 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.
  • If you have asthma or chronic obstructive pulmonary disease (COPD) and use a regular bronchodilator inhaler (a reliever that opens your airways, eg salbutamol or terbutaline), you should use it before inhaling your dose of Relenza.
  • This medicine only protects against flu for as long as you continue to take the medicine. For this reason it should not be taken as a general preventive measure to prevent swine flu during the current pandemic, as you would need to take it on a daily basis, potentially for months. This medicine should also not be used as a substitute for being vaccinated against seasonal flu. People who are at risk of complications if they contract seasonal 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 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 also not known how effective this medicine will be for preventing outbreaks of flu in nursing homes.

Use with caution in

  • Asthma (see warnings above).
  • Chronic obstructive pulmonary disease (COPD) (see warnings above).

Not to be used in

  • Known sensitivity or allergy to any ingredient.
  • Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption (Relenza inhalation powder contains lactose).
  • Relenza is not recommended for children under five years of age.

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 fully established. The manufacturer states that 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.
  • During the current swine flu pandemic it is recommended that pregnant women diagnosed with swine flu should take Relenza to treat the infection. This is because Relenza is taken by inhaler and easily reaches the throat and lungs, but doesn't enter the bloodstream or cross the placenta in significant amounts. As a result it should not pose any risk to the baby. An expert group has reviewed the risk of Relenza treatment in pregnancy and concluded that any risk of the medicine is extremely small compared to the risk posed by the symptoms of swine flu. Ask your doctor for further information if you are concerned.
  • It is not known the extent to which this medicine passes into breast milk. It may pass into the breast milk in small (insignificant) amounts. The manufacturer states that it is not recommended for use during breastfeeding unless the potential benefit to the mother outweighs any potential risk to the nursing infant. Ask your doctor for advice if you are breastfeeding.
  • During the current swine flu pandemic, the Department of Health states that it is safe for breastfeeding women to continue to breastfeed while taking a course of Relenza to treat swine flu. Ask your doctor for further information if you are concerned.

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. These are all very rare (affect less than 1 in 10,000 people). Just because a side effect is stated here 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 or hives.
  • Allergic reaction with swelling of the face or throat.

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?

Zanamivir is not known to affect other medicines.

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

If you need to take any other medicines by inhalation at the same time as Relenza, you should also take these before taking your dose of Relenza.

Other medicines containing the same active ingredient

There are currently no other medicines available in the UK that contain zanamivir as the active ingredient.