Relenza (generic name Zanamivir) is an inhaled medication used for treating and preventing influenza or the “flu.” Zanamivir suppresses and decreases the spread of influenza A and B viruses, the viruses responsible for the flu. It does this by blocking the action of neuraminidase, an enzyme produced by the viruses that enables the viruses to spread from infected cells to healthy cells. By preventing the spread of virus from cell to cell, the symptoms and duration of influenza infection are reduced.

Zanamivir is used for the treatment of infection with the influenza viruses, including H1N1, in individuals seven years of age or older with symptoms for no longer than two days. It also is used for preventing influenza in adults and children five years of age and older.

What is the usual dose?

Zanamivir is administered by oral inhalation. The recommended dose is two inhalations (5 mg per inhalation) twice daily (approximately 12 hours apart) for five days. Two doses (separated by at least two hours) should be administered on the first day of treatment. For best results, treatment should begin as soon as symptoms develop. The recommended dose for prevention of influenza in a household setting is 10 mg once daily for 10 days. The recommended dose for preventing influenza in a community setting is 10 mg once daily for 28 days.

What precautions must be followed with Zanamivir

Zanamivir potentially may interfere with the action of injections of live attenuated flu vaccine because zanamivir prevents viral replication. Therefore, live attenuated flu vaccine should not be administered within 2 weeks before or 48 hours after administration of zanamivir.

Preganacy and Breastfeeding

The Centers for Disease Control (CDC) states that pregnancy is not a contraindication for use of zanamivir in pregnant women because the benefits outweigh the risks. It is not known whether zanamivir is excreted in breast milk. However, the CDC recommends that women who develop flu after child birth should be treated with antiviral drugs.

What are Relenza side effects?

The most frequent side effects are headaches, diarrhea, nausea, cough, vomiting and dizziness. Sinusitis, ear, nose, and throat infections may occur. Skin reactions, allergic reactions, bronchospasms, and behavioral disturbances have been reported.

Patients with respiratory diseases may experience breathing problems when treated with zanamivir due to irritation of the breathing tubes by the particles from the inhaler. If breathing problems occur, zanamivir should be discontinued. Patients who have asthma or other breathing problems that make them sensitive to inhaled particles should have a fast acting, inhaled bronchodilator available to treat any breathing problem that may occur when zanamivir is used.