Zanamivir (Inhalation)

Zanamivir is an antiviral composed of neuraminidase inhibitors, designed to prevent the spread of the flu virus around the body. It can treat infections which arise as a result of viruses like influenza A, influenza B, and swine influenza.


Zanamivir assists those suffering from, or at risk of, various viruses in the influenza family. It works firstly as a preventative measure and is capable of preventing infection with different types of influenza in those who have come into contact with a carrier of the virus.

As well as working as a preventative drug, it can also assist those who have already contracted the virus to mitigate the side effects. It can hasten the reduction of the symptoms of flu, such as a cough, a fever, a sore throat and more by around one or one and a half days.

Its brand name in the USA is Relenza, which means you may see this name on the packaging in stores and pharmacies.

Conditions treated

  • Influenza A
  • Influenza B
  • Influenza H1N1 (swine flu)

Type of medicine

  • Inhalation

Side effects

Among patients who take Zanamivir, it is not common for them to experience any side effects.

There is a wide range of light side effects which can occur as a result of Zanamivir, but they are classified as less common due to their low incidence.

These include a range of flu-related symptoms, including dizziness, a fever, chills, and pain in the face and cheeks.

In this category, there is also a range of ear-related potential side effects. These include a change in hearing, ear drainage, ear pain and ear infections.

Related to this, a group of nose and throat problems are possible as a result of taking Zanamivir. These include a cough (either producing or not producing mucus), throat infections, nasal problems and a shortness of breath. You may also notice stomach problems, such as diarrhea, nausea and vomiting.

Most of the time it is not necessary to seek medical help in the event that these side effects occur, as they often go away quickly. They tend to simply be your body's natural response to the effects of the drug. However, if you are concerned about the side effects or wish to consider your options for mitigating them, then it may be a good idea to consult with your doctor or another medical professional before taking Zanamivir. In the event that the side effects do not go away or they are causing you a large degree of pain or discomfort, you should speak to your medical professional.

There are some rare side effects which patients may experience as a result of taking Zanamivir. In the event that you experience any of the following side effects, you should seek medical attention straight away and clearly state that you are taking Zanamivir.

Possible rare side effects include dizziness to the point of fainting, convulsions, joint pain and increased sensitivity to sunlight. Any increases or decreases in the speed of your heartbeat, or any changes to its regularity, are also possible side effects.

Rare side effects may also include a range of skin conditions. These include hives, reddened or flushed skin, or severe skin rashes.

You should also monitor your face, as in rare cases problems here may manifest themselves as side effects. These include puffiness of the face and itchy, painful or watery eyes.

Severe problems with your body's breathing apparatus are also rare possible side effects noted as a result of taking Zanamivir. These include a tight throat or chest, swollen glands and wheezing.

Finally, it is important to remember that all patients are unique and, as a result, it is also possible that some people will experience side effects which are not listed here. In the event that this happens to you, you should consult your doctor or other medical professional straight away.


Zanamivir is a prescription-only medication, which means it is only available from your physician. You should not take more than the dosage stated to you by your medical professional, and you should never take someone else's medication.

Although Zanamivir treats the symptoms of various types of influenza, it is not a substitute for your annual flu shot and you should always continue to take this unless advised otherwise by a medical professional.

When discussing your symptoms with your physician, you should inform them of any allergies you suffer from, such as reactions to dyes, foodstuffs or animals. If you've taken this medication before and suffered from any allergic reactions to it, you should alert your physician so that they can take this into account when describing what to prescribe.

Tell your physician if you have ever had any unusual or allergic reactions to this medicine or any other medicines. Also tell your healthcare professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

In the case of those who have not yet demonstrated symptoms of influenza A or influenza B viruses but who have come into close range with someone who has already suffered from one of them, they should ideally take Zanamivir within 36 hours of being exposed to a person with the virus. (For children older than five years, this should happen within 48 hours of exposure.)

For those who are already infected with either the influenza A or influenza B viruses, Zanamivir should again begin as soon as possible, but this time ideally within two days of symptoms appearing. Two doses can be administered on the first day of treatment, although two hours should be left in between.

In the case of the influenza H1N1 virus (also known as swine flu), the recommended timings are slightly different. Adult patients should ideally take Zanamivir within seven days if it is being taken as a preventative measure, while children should have their treatments launched within 48 hours. Once again, treatment should begin within two days of symptoms appearing in the event that the virus has already been contracted. Again, two doses can be administered on the first day of treatment on day one, although two hours should be left in between.

If Zanamivir is being used to treat larger groups during a community outbreak, treatment should commence within five days of the outbreak.

Usually, there are 20 units of five milligrams per every Rotadisk received in a prescription. For adults and children using Zanamivir as a preventative measure, the drug should be taken in 10 milligram doses for 10 days, regardless of the strain of influenza. For adults and children who are taking it as treatment when the virus has already infected them, 10 milligrams should be inhaled once every 12 hours for a five-day period.

In the event that you are seriously ill after five days, in some cases the dosages can be continued beyond this window. Remember, should you begin to experience fewer symptoms after taking Zanamivir, you should continue to take it for the entire period stated by your doctor, as this will ensure the infection is tackled completely. It is possible that the symptoms will begin again if you do not do this.

In the event of a missed dose, you should catch up by taking it as soon as possible. The only time this does not apply is if you realise within two hours of your next dose, in which case you should skip the missed one and take the next scheduled one as planned. You should never take double doses.

Loading and using the inhaler

Zanamivir comes in the form of an inhaler, rather than a liquid medicine or a tablet format. These instructions will show you how to prepare the inhaler for use and how to then take the medicine.

Firstly, you will most likely need to load the inhaler before you are able to use it. You should begin by removing the inhaler's blue cover and double-checking the area which will make contact with your mouth. You should confirm that the device is clean, and, if not, wipe it down carefully with a soft cloth. Ensure there are no foreign bodies around the mouthpiece.

Then, you should pull on the mouthpiece - which is usually colored white - until the tray on which you will later insert the disk comes out. You should gently hold (but not grip) the tray's corners and then remove it slowly until the bumpy ridges at the tray's edges are visible.

Once you have found the ridges, you should squeeze - again, gently - with your thumb and forefinger in an inward direction. The tray will eventually appear and protrude from the inhaler. If you are concerned about damaging the inhaler, don't worry: it's OK to continue to squeeze gently until the tray appears.

Once this has happened, you can insert one of the disks from the Rotadisk. Double-check at this stage that the inhaler is loaded with the correct dosages as prescribed by your medical professional. Once this is complete, simply push the tray back inside the body of the inhaler. It is now ready for use.

Next, you should familiarise yourself with how to use your loaded inhaler. Begin by holding out your hand and placing the inhaler flat, well away from your mouth for the moment. Inside the inhaler, the plastic which coats the medicine disk you just inserted will have been pierced by a needle, enabling the inhalation to take place.

In order to ascertain whether or not this has happened, you should check whether or not the flap has been raised as far as it can go. If it has, this signifies that the seal is broken and the medicine is ready to be inhaled. (Remember: do not raise the flap if there is no medicine inside the body of the inhaler. If you do this, you risk damaging the inhaler to the point where you need a replacement, and you may not be able to use it in time for your next dose.)

Once the seal is broken, you should close the lid of the inhaler. Following this, breathe out as normal then put the inhaler's mouthpiece inside your mouth and move your head backwards slightly.

It's important to ensure that you don't block the mouthpiece with your tongue, as this may impede the flow of the medicine, and you should also take care not to bite the inhaler or block any air vents on the sides of the inhaler. You should take a deep breath and hold it for as long as you find you can, although no longer than 10 seconds. Then, you can breathe out and repeat the process with a new disk if you are taking a second dose.

Once you have finished, you should wipe down the mouthpiece and put the cover back on in order to prevent any dirt building up.

Interactions: All drugs, including Zanamivir, can interact with other drugs you are currently taking once they are all inside your body. This can sometimes lead to adverse consequences, so it's important that a list of any and all medications you're currently taking is maintained. You should be aware of this list yourself, but it should also be a part of your medical notes.

Your medical professional should always be fully aware of any drugs you are currently on, and if there is something which they may be unaware of, it's vital you inform them in order to prevent any complications arising as a result of taking Zanamivir.

The other medications which Zanamivir has been known to interact with include:

  • Afrezza (insulin inhalation, rapid acting)
  • Exubera (insulin inhalation, rapid acting)
  • FluMist (influenza virus vaccine, live, trivalent)
  • FluMist Quadrivalent (influenza virus vaccine, live, trivalent)


It is important to take the appropriate care and pay attention to labels, information booklets and instructions from your physician when taking Zanamivir.

Firstly, ensure that you see your medical professional following a course of Zanamivir in order to ensure that the medication worked correctly, your virus is now gone and that the medication has not left any lasting effects on your health.

Be aware that taking Zanamivir only protects against the stated strains of influenza. Many bacterial infections begin with similar symptoms to influenza, but taking Zanamivir does not prevent these conditions from developing. Your medical professional will be able to diagnose bacterial infections and distinguish them from influenza to ensure you receive the correct medicine.

There are also some specific warnings regarding Zanamivir. If you suffer from lung disease, for example, Zanamivir may cause problems such as wheezing and shortness of breath. If this happens to you when taking Zanamivir, you must stop using the medication and seek urgent medical attention.

You may also find that this medication leads to a range of mood disorders, such as irritability and agitation. In the event that you or a loved one observe these behaviours, you should continue to take the medicine but speak to your medical professional immediately.

If you suffer from chronic respiratory disease or asthma, there is a risk that taking Zanamivir could cause problems such as bronchospasm (also known as wheezing). In the event that this risk materialises and you suffer from wheezing, you should take an inhaled bronchodilator. Ensure that this is a fast-acting device in order to experience maximum relief, and make sure it is kept with you while you take Zanamivir to prevent any issues.

In some cases, taking Zanamivir may result in allergic reactions such as anaphylactic shock. Symptoms of this can include hives, trouble breathing, itching, hoarseness and more. In the event that you notice these symptoms while taking Zanamivir, you should cease to use it and alert your medical professional right away as anaphylaxis requires urgent treatment to prevent further problems.

If you are planning to take the live nasal flu vaccine FluMistĀ®, you should inform your physician right away. This drug interacts with Zanamivir, and patients should not take FluMistĀ® in the two weeks running up to starting a course of Zanamivir or for two days after taking it.

This is not an exhaustive list of potential problems, so you should always speak to your medical professional first before going ahead with Zanamivir.


Keeping your Zanamivir stored in the correct way is essential for ensuring it retains its useful qualities. If you do not store your Zanamivir correctly, you may risk rendering it useless.

You should always keep the Zanamivir in its foil casing until it is time to use it. Ensure it is kept at room temperature rather than in extremes of heat: this means it should be kept out of direct light, and should also not be frozen.

Once you no longer require Zanamivir, ensure you dispose of it rather than continue to store it. You should also do this with the packaging, including the inhaler. If you are unsure as to how to safely dispose of your medicines, you should speak to your medical professional for advice.

As with all medicines, ensure you keep them out of the reach of children in order to prevent accidental or dangerous consumption.


Zanamivir is an effective medicine which can greatly assist those suffering from various strains of influenza, and provide them with much-needed respite. It is also helpful in the prevention of the spread of the disease and can be used both in individual cases and in entire communities.

Zanamivir does not bring with it a host of common side effects, but there are still risks involved with taking this medicine. Even though they are less common risks, they should still be taken seriously. In order to mitigate against these risks, patients should effectively communicate with their medical professionals and provide full lists of current medication and medical history in order to prevent drug interactions and other problems.

Potential side effects of Zanamivir are diverse and can range from serious complications such as anaphylaxis, difficulty breathing and convulsions to less serious conditions such as nausea and coughing. In the event of less serious side effects being observed, patients should wait to see if the side effects go away, and only approach their medical professional if the effects are causing extended distress or do not go away.

Zanamivir is consumed via an inhaler, and patients should always take great care when using their inhalers. Incorrect use of an inhaler can quickly result in damage to the item, which can delay treatment and mean patients find that their recovery is delayed.

There is a standard dosage for Zanamivir, and this should always be followed. In the event that the patient is still ill, the dosage can be extended - but a medical professional should always make this decision.

Last Reviewed:
December 24, 2017
Last Updated:
April 05, 2018
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