ZANAMIVIR is an antiviral medicine. It is used to prevent and treat flu infections caused by influenza A or B virus. It will not work for colds, other types of flu, or other viral infections. Compare neuraminidase inhibitors.

Relenza Side Effects

What should I watch for?

Tell your doctor or healthcare professional if your symptoms do not start to get better or if they get worse.

If you have asthma, chronic bronchitis, or emphysema you may be at a higher risk for having breathing problems while you are taking this medicine. Make sure to have a fast acting inhaler to treat breathing problems. If your symptoms get worse or if you need your short acting inhalers more often, call your doctor right away.

If you have the flu, you may be at an increased risk of developing seizures, confusion, or abnormal behavior. This occurs early in the illness, and more frequently in children and teens. These events are not common, but may result in accidental injury to the patient. Families and caregivers of patients should watch for signs of unusual behavior and contact a doctor or health care professional right away if the patient shows signs of unusual behavior.

To treat the flu, start taking this medicine within 2 days of getting flu symptoms.

This medicine is not a substitute for an annual flu vaccine.


Interactions with Medications

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:



dizziness and fainting

fast, slow, or irregular heartbeat

flushing or reddening of the skin

increased sensitivity to sunlight

itching, pain, redness, swelling, or watering of the eye or eyelid

joint pain

severe skin rash or hives

shortness of breath or troubled breathing

swelling or puffiness of the face

swollen glands or tightness in the throat

tightness in the chest or wheezing

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

Change in hearing


cough producing mucus



ear drainage

ear, nose, and throat infections


fever or chills


nasal signs and symptoms


pain and pressure over cheeks

pain in the ear

shortness of breath


Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

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