zanamivir: clinical use

Prescribing considerations

• Confirm that influenza is circulating and apply current public-health recommendations.
• Ensure the patient can use the Diskhaler effectively.
• Evidence is limited in severe or unstable chronic illness, immunocompromised patients, nursing-home prevention and older adults.
• Assess carefully in asthma, COPD or other respiratory disease because acute bronchospasm and deterioration in respiratory function have occurred.
• The product does not replace influenza vaccination.

Contraindications and cautions

• Hypersensitivity to zanamivir or an excipient.
• Milk-protein allergy.
• The lactose-containing product should not be used in total lactase deficiency, galactose intolerance or glucose-galactose malabsorption.

Monitoring

• Check inhalation technique and ability to operate the device.
• Monitor respiratory symptoms, particularly with asthma, COPD or other airway disease.
• Monitor for behavioural or neurological changes, especially in children and adolescents.
• Assess clinical deterioration promptly because zanamivir is active only against influenza viruses.

Clinical pharmacology

Zanamivir acts extracellularly as a selective influenza neuraminidase inhibitor. Inhalation deposits it in the respiratory tract. Systemic absorption and protein binding are low; it is not metabolised, and absorbed zanamivir is excreted unchanged by renal filtration.

Formulation and product differences

• The inhaled product is a pre-dispensed lactose-containing dry powder used with a Diskhaler.
• The powder must not be converted into a solution or delivered by nebulisation or mechanical ventilation.
• Intravenous zanamivir is a separate formulation used in different clinical circumstances and is not interchangeable with the inhalation powder.

Inhaled preparation

Route: Inhaled

Strengths: 5 mg/dose