Zanamivir

How it works

It inhibits the influenza viral neuraminidase enzyme, preventing release of newly formed virions from infected cells and limiting spread within the respiratory tract.

Prescribing in practice

• Inhaled zanamivir can precipitate bronchospasm and should be used with caution, and generally avoided, in people with asthma or chronic obstructive pulmonary disease who should have a short-acting bronchodilator available.
• It is most effective when started as early as possible after symptom onset, in line with NICE criteria for antiviral use during influenza circulation.
• The lactose-containing inhalation powder must not be reconstituted and given through a nebuliser or mechanical ventilator.

Monitoring

No routine laboratory monitoring is required; observe for respiratory deterioration after inhalation and for neuropsychiatric symptoms.

Counselling the patient

• Use a short-acting reliever inhaler first if you have asthma and have it to hand.
• Start treatment as soon as possible after symptoms begin for best effect.
• Stop and seek advice if you develop wheeze or breathing difficulty after inhaling the dose.

Evidence & guidelines

Use is supported by NICE technology appraisal guidance on antivirals for influenza.