An inhaled anti-flu antiviral
Zanamivir
An inhaled antiviral that can shorten flu and help protect people at higher risk, if started early.
What is Zanamivir?
Zanamivir is an antiviral medicine for influenza (flu), usually breathed in as a powder. It can shorten symptoms and help prevent flu in people at higher risk, but only if started very soon after symptoms begin. It is not a substitute for the flu vaccine.
Education and reference only. This is a plain-language guide to Zanamivir — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Zanamivir is a neuraminidase inhibitor used to treat and sometimes prevent influenza. In the UK it is most often given as an inhaled powder, with a form for injection reserved for serious hospital cases. It is used in flu season, particularly for people at higher risk of complications.
How it works
Flu viruses use an enzyme called neuraminidase to release newly made virus from infected cells so it can spread. Zanamivir blocks this enzyme, trapping new virus particles and slowing the infection. Because it acts on virus that is already multiplying, it works best when started within about two days of the first symptoms.
Company & origin
Originated / developed by: Developed by GlaxoSmithKline..
Approved in the late 1990s and used in the UK for influenza, mainly inhaled.
Practical use
How to take Zanamivir
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Start it as soon as possible after flu symptoms begin, ideally within about two days.
- Breathe the powder in using the supplied inhaler device exactly as shown.
- If you use a reliever inhaler, take it before zanamivir and keep it nearby.
- Complete the full course even if you start to feel better.
- Stop and seek advice if you wheeze or your breathing tightens after a dose.
- Do not rely on it instead of the flu vaccine for prevention.
Weighing it up
Advantages & disadvantages of Zanamivir
Advantages
- Can shorten flu and ease symptoms when started early.
- Inhaled delivery means little is absorbed into the rest of the body.
- Useful for people at higher risk of flu complications.
Disadvantages
- Only worthwhile if started very soon after symptoms begin.
- The inhaled powder can rarely trigger wheeze, so needs caution in asthma or COPD.
- Requires good inhaler technique, which can be hard for some people.
Practical use
Good to know
Start zanamivir as soon as possible, ideally within about two days of flu symptoms beginning, or it is much less effective. As an inhaled powder it can rarely cause wheeze or tighten the airways, so it should be used with caution by people with asthma or COPD, who should keep a reliever inhaler to hand. It does not replace the annual flu vaccine.
Who should not take it / use with caution
- People who are allergic to zanamivir or to milk proteins, which the powder can contain.
- People with severe asthma or COPD may be better suited to a different antiviral.
- Very young children who cannot use the inhaler properly.
Monitoring
- Watch breathing closely in people with asthma or COPD.
- Check that symptoms are improving as expected.
- Seek urgent help for severe breathlessness or an allergic reaction.
Side effects
- Wheeze or tightness in the chest, particularly in people with airway disease.
- Headache and a stuffy or runny nose.
- Rarely, rash or other allergic reactions.
Key interactions
- Few significant drug interactions.
- Live flu vaccine given by nasal spray may work less well around the time of treatment.
- Tell your prescriber about any inhalers or breathing medicines you use.
Available as: Available as an inhaled powder, with an injection/infusion form reserved for serious hospital cases.
Answers
Zanamivir: frequently asked questions
How soon must I start zanamivir?
As early as possible, ideally within about two days of your first flu symptoms. Started later, it has little benefit.
Can people with asthma use it?
It can sometimes be used with caution, but the inhaled powder may cause wheeze, so people with asthma or COPD should keep a reliever to hand and may be offered a different antiviral.
Does zanamivir replace the flu jab?
No. It treats or helps prevent flu after exposure, but it does not provide the lasting protection of the annual flu vaccine.
How is it taken?
Usually as a powder breathed in through a special inhaler device. Good technique matters, so ask your pharmacist to show you how.
Will it cure flu instantly?
No. It can shorten the illness and ease symptoms when started early, but you will still need rest, fluids and time to recover.
The wider class
About Influenza antivirals
Zanamivir belongs to the influenza antivirals class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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