Relenza Dosing and Side Effects

Relenza is a pharmaceutical product that contains the active drug zanamivir. It is designed for oral inhalation to optimize its pharmacokinetic properties and allow the drug to act where it is needed in the respiratory tract.

Zanamivir may also have adverse effects on the body for some people, with potentially severe outcomes for patients that suffer from asthma or emphysema due to the oral inhalation method.

Administration of Dose

Relenza is available as a powder to be inhaled via the mouth. For optimal results in the treatment of influenza, it should be inhaled twice daily for five days. It is best if the doses are spread out throughout the day, ideally every 12 hours, once in the morning and once at night. It may also be beneficial to provide a loading dose on the first day of treatment, with more frequent dosing to allow the drug to exhibit an effect in your respiratory tract.

The antiviral drug can also be used to prevent influenza, such as for people sharing a household with someone infected with the flu. In this case, a once daily dose is usually sufficient for about ten days, until the infection has passed. It can be taken for a longer period of time, for example for one month, to prevent the spread of influenza amongst a community.

Zanamivir has a low bioavailability of 2% and with administration via inhalation only 15% of the drug is absorbed and excreted in the urine. This suggests that the majority of the drug remains in the respiratory system, where it will have the most beneficial effect and reduces the risk of systemic side effects.

Inhalation Device

As Relenza is administered by inhalation, it comes with a plastic Diskhaler to inhale each dose and five Rotadisks that contain four doses of the medication in separate blisters of a circular pack.

It is important the patients are clear about the correct technique of using the inhaler, to ensure each dose is being delivered correctly. Often if is helpful for a health profession to give a demonstration of how to use the advice, in addition to explaining the manufacturer’s instructions, as it reduces the risk of error.

If the patient also needs to take another inhaled medication, such as for asthma or emphysema, the regular medication should be administered first, followed by the inhalation of zanamivir.

Side Effects

Zanamivir may have adverse effects in some patients, which are outlined below:

• Dizziness
• Nasal irritation
• Joint pain

Additionally, it is possible for people to be allergic so zanamivir or the other pharmaceutical components that it contains. It is for this reason that patients taking the medication for the first time should be particularly aware of any signs that may indicate an allergic reaction. These may include:

• Hives
• Rash
• Itching
• Swelling

As a result of the inhaled administration of the drug, it may also cause serious effects for people that are susceptible to conditions of the airways, such as asthma and emphysema. This may result in bronchospasm, which requires immediate medical attention. The following signs may be indicative of bronchospasm:

• Difficulty breathing
• Wheezing
• Shortness of breath

If bronchospasm is suspected, a medical advice should be sought as soon as possible for appropriate management.

References

• 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
• http://www.nlm.nih.gov/medlineplus/druginfo/meds/a699021.html