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What is Relenza®?

Tricia Christensen
Updated May 17, 2024
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Relenza® is a medication produced by GlaxoSmithKline®, also known by the generic name zanamivir. It helps fight the flu virus in the body and when appropriately used by people who will not have bad reactions to the drug, it can be very useful in preventing the progression of influenza, and reducing the number of days a person is ill. Zanamivir can also prevent people from having an infection develop if they receive this medicine after close exposure to others with the flu.

Relenza® is often compared to Tamiflu®, and one difference is the means of administration. Zanamivir is an inhaled powder and Tamiflu® is usually give in tablet form. Certain studies suggest another valuable point of comparison. It appears that most strains of flu may have some resistance to Tamiflu® but few are resistant to Relenza®. With both flu-fighting agents, these drugs are best administered at the first signs or within a day or two of noting an influenza infection. They usually aren’t as effective when people have had the flu for more than a couple of days.

There are a few groups who should not use Relenza®. These include sufferers of asthma, and those with chronic obstructive pulmonary disorder. Anyone else with a chronic respiratory condition is advised not to take zanamivir.

The reason for this contraindication is that the medicine has been occasionally associated with life-threatening breathing problems. In any case, it’s been shown to not work effectively in people with breathing issues. Zanamivir is additionally contraindicated in women who are pregnant or nursing, and it usually isn’t used in very young children.

A fair number of people who take Relenza® develop some side effects. These may recede within a few days after doses begin, or remain until the course of the medication is finished. In the first few days, some of the commonly reported side effects are headache and nausea or vomiting. Some people without previous respiratory issues do suddenly develop breathing problems when taking this medicine, and they are urged to seek medical advice immediately and refrain from additional doses until after seeing a doctor.

Other side effects that have been reported with Relenza® are rashes and itching, nasal congestion, sinus infections, a sense of dizziness, sore throat, and mild cough. As mentioned, most side effects don’t occur often, or aren’t very severe. On occasion, an allergic reaction to zanamivir may occur. If people note signs of anaphylactic allergy such as hives, wheezing or difficulty breathing, and swelling of the face, lips, or tongue, they need emergency medical help.

Organizations like the Centers for Disease Control (CDC) approve of medications like Relenza®, particularly to treat those who may suffer complications from the flu. They are nevertheless quick to observe that though this medicine has a brief, preventative effect, it isn’t a good substitute for yearly flu vaccinations. People are still strongly advised to prevent the flu with vaccination first, relying on flu medicines only if that vaccination is ineffective.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Tricia Christensen
By Tricia Christensen , Writer
With a Literature degree from Sonoma State University and years of experience as a WiseGeek contributor, Tricia Christensen is based in Northern California and brings a wealth of knowledge and passion to her writing. Her wide-ranging interests include reading, writing, medicine, art, film, history, politics, ethics, and religion, all of which she incorporates into her informative articles. Tricia is currently working on her first novel.

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Tricia Christensen

Tricia Christensen


With a Literature degree from Sonoma State University and years of experience as a WiseGeek contributor, Tricia...
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