August 1999
ROCKVILLE, Md. - Zanamivir for inhalation (Relenza, Glaxo Wellcome) was recently approved by the Food and Drug Administration (FDA) for the treatment of uncomplicated influenza virus infection in adults and children 12 years and older.
Zanamivir was approved to treat type A and B influenza, although the FDA Antiviral Drugs Advisory Committee recommended against approval. The principal trials enrolled more than 1,000 patients with type A influenza; only about 120 had type B influenza. Zanamivir is the first approved drug for the treatment of influenza since the approval of rimantadine (Flumadine, Forest) in 1993.
Clinical studies determined that patients with influenza who received zanamivir had shorter improvement times for influenza symptoms. Part of the evidence for efficacy was provided by studies in the Southern Hemisphere and Europe. Efficacy treatment studies enrolled more than 1,500 patients with influenza-like illness.
Effectiveness was demonstrated only in patients who started treatment within two days of symptoms. Zanamivir appears less effective in patients who do not have severe symptoms.
In patients with severe or decompensated asthma or chronic obstructive pulmonary disease, the FDA said. Bronchospasm was documented in some patients with mild or moderate asthma following administration of zanamivir. Any patient who develops bronchospasm should stop using the drug and call their health care provider. Patients with underlying respiratory disease should be instructed to have a fast-acting inhaled bronchodilator available when they are being treated with zanamivir. This product has not been shown to be effective, and may carry risk.
Relenza is taken twice daily for five days using a breath-activated plastic inhaler device called a Diskhaler. The device holds a Relenza Rotodisk, which is a blister package containing a powder mixture of zanamivir and lactose. After a disk is loaded into the Diskhaler, a blister is pierced and the drug treatment is released into the air stream created when the patient inhales through the mouthpiece.
Physicians should accurately inform their patients of the proper use of the inhaler before using this product, including a demonstration whenever possible, according to the FDA.
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