How to Use Relenza to Treat the Flu

There are several options for antiviral treatments if you have the flu. The most commonly prescribed is Tamiflu, but another option is a medication called Relenza (zanamivir). This antiviral flu medicine is inhaled through the mouth, similar to an inhaler that is used for asthma.

Woman lying on the couch with the flu

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Who Can Use Relenza

Relenza is approved for use by adults and children over 7 years old. It can be used to treat the flu if you start taking it within 48 hours of the start of your symptoms. It can also be used to prevent the flu if you are in close contact with someone who has it. If it is being used for flu prevention, it can be used by children as young as five.

Dosing differs depending on what you are using Relenza for. If you are taking it to treat your flu symptoms, the recommended dosing is to take it twice a day (about 12 hours apart) for 5 days.

If you are taking it to prevent influenza and someone in your home is already sick with it, Relenza is usually taken once a day for 10 days.

Some people who are at high risk for complications from the flu may take antiviral medications to prevent the flu when there is an outbreak in the community. In those cases, it may be recommended that you take Relenza once a day for 28 days.

It's important to take the medicine at about the same time every day. This allows a consistent amount of medication to remain in your body, increasing its effectiveness.

Who Shouldn't Use Relenza

It is not approved for use by children under the age of 7.

Because Relenza is an inhaled medicine, people with asthma or chronic lung diseases should not use it. It also should not be used by those who have lactose (a sugar in milk and dairy products) allergy because the medicine contains lactose.

If you are pregnant or nursing, talk to your doctor about the pros and cons of taking Relenza. The flu can be very serious or even life-threatening for women who are pregnant. Your healthcare provider can help you decide which treatment is right for you.

Side Effects

Every medication causes side effects in some people. The most commonly occurring side effects in those taking Relenza include:

  • Diarrhea
  • Nausea
  • Vomiting
  • Headache
  • Dizziness
  • Nasal irritation
  • Cough
  • Ear, nose or throat infections

If you or your child is taking Relenza and you experience one of these side effects, don't panic. Most of the time, these side effects will be mild and may not even be noticeable as many are symptoms of the flu as well. If you notice a significant difference in your symptoms after you start taking the medicine that concern you, contact your healthcare provider. 

Occasionally, people may experience more serious adverse effects while taking Relenza.

These may include:

  • Difficulty breathing - Most often in those with lung diseases such as asthma.
  • Seizures, confusion or abnormal behavior - These have occurred in children and teenagers being treated for the flu and those who have the flu but are not taking any antiviral medicines. Injury or death can occur due to these conditions. If you see these occur, contact a healthcare provider or seek medical attention right away.
  • Allergic reaction - Severe allergic reaction can occur when taking this medicine. If you experience dizziness, difficulty breathing, swelling of the mouth or tongue, hives, difficulty swallowing, hoarseness, wheezing, or shortness of breath, seek medical attention immediately. If you are allergic to components of the medication, you should not take Relenza.

It's important to know that these serious adverse events are very rare. It's important to know what to watch for, but the chances that you or someone you know will experience any of these is extremely low.

How to Use Relenza

If you are prescribed Relenza, your healthcare provider or pharmacist should demonstrate how to take it. The medicine is administered through a device called a diskhaler. There are blister packs inside the diskhaler that have a powdered medicine in them that is inhaled through the mouth. How often you use it depends on whether you are taking Relenza to treat or prevent the flu.

You should not take Relenza if you have not been instructed how to use it or don't understand the instructions.

Is It Better Than a Flu Shot?

Antiviral medicines, including Relenza, are not a substitute for flu vaccines. The flu vaccine is the best way to prevent the flu.

However, some people may not be able to get flu vaccines due to allergies or other medical concerns. If you are not able to get vaccinated and you are at high risk for complications from the flu, using an antiviral medicine may be an option to keep you from getting sick.

It's also important to use basic infection prevention techniques, like washing your hands frequently, avoiding those who are sick, and using hand sanitizer when soap and water aren't available.

How to Choose Which Antiviral Treatment Is Best

All antiviral flu medicines are available by prescription only. Talk to your healthcare provider about your options and together, you can decide which one is right for you. If you can start taking it within the first 48 hours of the onset of your flu symptoms, it is more likely to help you feel better faster.

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