Zanamivir, Relenza

Zanamivir, Relenza ® and Antiviral Drugs Used to Treat Influenza: Zanamivir, Relenza®, produced by GlaxoSmithKline is an antiviral drug used to treat influenza A and B. The drug is a neuraminidase inhibitor and shares this category with oseltamivir, known as Tamiflu®, produced by Hoffman La Roche Inc. Lately the drug, which is not yet produced generically, has been catapulted to drug fame for its potential in treating the H5N1 subtype of Influenza A, bird flu, the next candidate for a pandemic flu. The availability of zanamivir is very limited.

Indications and Mechanism of Action: Zanamivir is used to treat Influenzas A and B administered within 48 hours of the onset of symptoms. It is also used to prevent the spread of the flu to other people. So far no viral resistance to zanamivir has been reported in laboratory studies. Neuraminidase inhibitors attack the N component of influenza, neuraminidase, a surface antigen on the influenza A and B viruses that allows newly formed viruses (virons) to be released from host cells to infect healthy cells.

Not a Subtitute for a Flu Shot: Zanamivir is intended to treat flu, not prevent it. The best prevention of influenza is a vaccine. The seasonal flu shot is a vaccine against three different types of flu, two Influenza A subtypes and one strain of Influenza B. Although the seasonal flu vaccine will not prevent you from contracting the H5N1 bird flu virus, it can prevent you from getting both viruses at the same time. At this time a pandemic flu vaccine does not exist.

Use in Children: Zanamivir has been used in children 7 years-old and older. Contact your doctor for their recommendations of using zanamivir in children. In general, zanamivir seems to be well-tolerated by children and adults, but it can produce produce cough, bronchospasms and reduced pulmonary function in some people (this is not permanent). So, it's a good idea to have a fast-acting bronchodilator inhalor in case it's needed.

Contraindications: Caution should be taken with those with chronic lung diseases (asthma, bronchitis, emphesyma, etc.), severe heart or kidney disease, or those with allergies to zanamivir or any component of Relenza ®, and for those women who are pregnant, trying to get pregnant and/or breast feeding. Contact your doctor if you have difficulty breathing or have bronchospasms after taking zanamivir. If you sometimes need a bronchodilator inhaler, make sure it's handy when you administer zanamivir.

Approved Dosage of Zanamivir: The normal dosage is two inhalations twice daily (morning and nighttime for example) for 5 days. On the first day you need to take two doses (two inhalations) two hours apart. Read the instructions on how to use the Diskhaler® device and load the Rotadisk® with the drug. If you use a bronchodilator inhaler, use it first and then a few minutes later take zanamivir. Zanamivir is not available orally, but only as an inhalable powder.

Zanamivir in the Treatment of Bird Flu: Inhaled zanamivir has not been studies for H5N1 treatment in humans, but the H5N1 virus is susceptible to zanamivir in laboratory studies in mice. It is suspected that like oseltamivir, a higher dose than the approved one may be needed to treat H5N1 infection in humans. In any case, treatment is more likely to be successful if started within 48 hours of the onset of symptoms.

Dosage of Zanamivir for Bird Flu: Until otherwise noted, the approved dosage for treating seasonal influenza is recommended.