How does this medication work? What will it do for me?

Zanamivir belongs to the family of medications called antivirals. It is used to treat flu infections caused by two influenza viruses (influenza A and influenza B) for adults and children 7 years of age and older. It is also used to prevent or reduce the chance of getting the flu in household and community settings (but not in nursing homes) following close contact with an infected person.

Zanamivir works by inhibiting an enzyme the flu virus needs to spread through your body. If it is used within 2 days of the start of flu symptoms, zanamivir can reduce the time it takes for flu symptoms to improve by about one day.

This medication does not replace the flu shot. You should get an annual flu shot according to immunization recommendations from your doctor.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each Relenza Rotadisk consists of a circular foil disk with 4 regularly distributed blisters each containing 5 mg of zanamivir. A diskhaler inhalation device is provided to administer the medication. Nonmedicinal ingredient: lactose.

How should I use this medication?

The recommended dose of zanamivir to treat influenza in adults and children 7 years and older is 20 mg, taken as 2 puffs in the morning and 2 puffs in the evening for 5 days. You should start the medication within 2 days of when you start to feel flu symptoms. The 2 doses should be as close to 12 hours apart as possible and the first 2 doses should be taken on the first day of treatment as long as there is at least 2 hours between the doses.

The recommended dose of zanamivir to prevent influenza in adults and children 7 years and older is 10 mg, taken as 2 puffs once a day at the same time each day for 10 to 28 days. The length of treatment will depend on the person and will be determined by your doctor.

Zanamivir is used with a special inhaler. Read the directions in the package carefully before using it. Ask your pharmacist if you have any questions about how to use the inhaler.

To load the inhaler with the medication:

  • Pull off the blue cover. Make sure the mouthpiece is clean and free of foreign objects. Pull the white mouthpiece until the tray is extended.
  • Hold the corners of the white tray and pull out gently until you can see all the raised ridges on the sides of the tray.
  • Put your finger and thumb on the ridges, squeeze inward, and gently pull the tray out of the body of the inhaler.
  • Place a disk on the wheel and then slide the tray back into the inhaler until it clicks firmly into place.
  • To replace the empty disk with a full disk, follow the same steps you used to load the inhaler.

To use the inhaler:

  • Hold the inhaler flat in your hand. Do not turn it over or drop it because the medication (which is a loose powder in the inhaler) may spill out.
  • Lift the flap. When the flap is raised as far as it will go, a plastic needle will break a blister containing one inhalation of medication. Do not lift the flap if the cartridge is not in the inhaler. Doing this will break the needle and you will need a new inhaler.
  • After the blister is broken open, close the lid. Keeping the inhaler flat and well away from your mouth, breathe out to the end of a normal breath.
  • Raise the inhaler to your mouth and place the mouthpiece in your mouth.
  • Close your lips around the mouthpiece and tilt your head slightly back. Do not bite down on the mouthpiece. Do not block the mouthpiece with your teeth or tongue. Do not cover the air holes on the side of the mouthpiece.
  • Breathe in through your mouth as steadily and as deeply as you can until you have taken a full deep breath.
  • Hold your breath and remove the mouthpiece from your mouth. Continue holding your breath as long as you can (for at least 3 seconds and up to 10 seconds) before breathing out. This gives the medication time to settle in your airways and lungs.
  • Hold the inhaler well away from your mouth and breathe out to the end of a normal breath.
  • Prepare the cartridge for your next inhalation. To automatically advance to the next blister, pull the white tray by the edges until it stops (don't remove it).
  • Take the second puff following exactly the same steps you used for the first puff.
  • When you are finished, wipe off the mouthpiece and replace the cover to keep the mouthpiece clean and free of foreign objects. You may drink water afterwards.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to use this medication exactly as prescribed by your doctor. If you miss a dose, administer it as soon as possible and continue with your regular schedule. If it is almost time for your next dose (within 2 hours), skip the missed dose and continue with your regular dosing schedule. Do not administer a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature in a dry place and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not use this medication if you are allergic to zanamivir or any ingredients of the medication.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • body pain
  • cough
  • decreased appetite
  • diarrhea
  • dizziness
  • fatigue
  • headache
  • irritation or inflammation of the nose
  • nausea
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • bronchitis
  • ear, nose, and throat infection
  • fever or chills
  • lightheadedness
  • skin rash

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • difficulty breathing and wheezing
  • signs of a severe skin reaction such as blistering, peeling, a rash that looks like small targets, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
  • symptoms of an allergic reaction (e.g., swelling of the hands, feet, ankles, face, lips, mouth, or throat; difficulty breathing or swallowing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Asthma or breathing disorders: This medication can cause serious breathing problems (wheezing, difficulty breathing). If you do take this medication and you have asthma or COPD, make sure you have your fast-acting bronchodilator available. If your dosing schedule requires both your bronchodilator and zanamivir to be used at the same time, use your bronchodilator first.

If you develop worsening breathing problems such as difficulty breathing, shortness of breath, or wheezing, stop using zanamivir and contact your doctor as soon as possible. Zanamivir is generally not recommended for people with a history of breathing disorders (e.g., asthma, COPD).

Effectiveness: Zanamivir is not effective for treating flu symptoms that have been present for more than 2 days.

Flu shots: Zanamivir is not a substitute for the flu shot. Continue to receive an annual flu shot as advised by your doctor.

Lactose: This medication contains lactose.  People who are allergic to milk proteins should not use zanamivir.  

Mental health: There have been reports of people who experienced delirium and abnormal behaviour while taking zanamivir. The exact link between zanamivir and these behaviours have not been established. If you experience any changes in behaviour, contact your doctor as soon as possible.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if zanamivir passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children under 7 years of age.

What other drugs could interact with this medication?

For a full list of interactions, use the Drug Interaction Checker available on the website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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