What is Relenza?

Relenza is the trade name of the drug that contains zanamivir, a neuraminidase inhibitor and antiviral drug used in the treatment and prevention of influenza. It is an orally inhaled drug, providing direct access to the respiratory system where the influenza virus usually resides and replicates.

Drug Discovery and Licensing

Relenza was discovered by Australian company Biota in 1989, who then sold licensing rights to GlaxoSmithKline (GSK) in 1990. The drug was made available for public use in 1999 and was the first neuraminidase inhibitor licensed for public use, followed closely by a second drug oseltamivir (trade name Tamiflu) a few months later.

Mechanism of Action

Relenza works by binding to and blocking the active site to the neuraminidase protein of the host cell. Its role as a receptor antagonist inhibits the influenza virus from being able to escape the host cell when the resources are completed. As a result, the virus dies along with the host cell and is unable to continue replicating the virus in subsequent host cells.

Research has shown the Relenza is able to reduce the duration of symptoms of influenza, as well as reduce the incidence of influenza infection when taken as a preventative method. There are no quality studies, however, to support the claim that Relenza helps to reduce complications of influenza like pneumonia.

In contrast to other neuraminidase inhibitors such as Tamiflu, there have been no strains of influenza to date that have shown signs of resistance to Relenza. This is a big benefit, as the drug is useful across a broad spectrum of influenza viruses and has the potential to help many individuals with symptoms of the flu.

Administration of Dose

Relenza is administered via oral inhalation and each package includes a Diskhaler for the correct administration. The dose is formulated as a dry powder that is inhaled directly into the respiratory tract where it helps to treat and prevent infection of influenza.

For the treatment of influenza, it is recommended that two doses of Relenza be inhaled twice a day, usually twelve hours apart. This should be continued for five days, even if symptoms have already resolved to prevent infection recurrence.

If the medication is being used as a preventative, a once daily dose should be sufficient and may be taken for a longer period of time. It is not uncommon for people within a community affected by influenza to take the medication for a month as a preventative measure.

Side Effects and Safety Precautions

Some patients that take Relenza may notice adverse effects such as dizziness, nasal irritation and joint pain. Allergy to zanamivir or other components in the medication is also possible and people who notice signs of allergy should seek immediate medical attention. Patients may notice signs of:

• Hives
• Rash
• Itching
• Swelling

Additionally, the inhaled formulation of Relenza may cause patients with certain medical conditions of the airways like asthma and emphysema to experience a flare up of symptoms. This can lead to bronchospasm, which is a serious condition requiring emergency medical attention. If individuals notice these signs, they should see a doctor as soon as possible:

• Difficulty breathing
• Wheezing
• Shortness of breath

Whilst not common, the severity of this effect warrants close attention and monitoring of people who are at risk of bronchospasm.

References

• http://www.nlm.nih.gov/medlineplus/druginfo/meds/a699021.html
• http://www.nejm.org/doi/full/10.1056/NEJMra050740
• https://www.gsksource.com/pharma/content/dam/GlaxoSmithKline/US/en/Prescribing_Information/Relenza/pdf/RELENZA-PI.PDF
• http://www.medicines.org.uk/emc/medicine/2608