Zanamivir

Allergic-like reactions, including anaphylaxis, oropharyngeal edema, and serious skin rashes have been reported.

Rare occurrences of neuropsychiatric events (including confusion, delirium, hallucinations, seizure, and/or self-injury) have been reported, primarily in pediatric patients; may be abrupt in onset. Direct causation is difficult to establish; influenza infection may also be associated with behavioral and neurologic changes.

Bronchospasm, including serious cases and some with fatal outcomes, and decreased lung function have been reported in patients with and without airway disease; discontinue with bronchospasm or decreased lung function. For a patient with an underlying airway disease where a medical decision has been made to use zanamivir, a fast-acting bronchodilator should be made available. Disease-related concerns:

Not recommended for use in patients with underlying respiratory disease, such as asthma or COPD, due to lack of efficacy in influenza treatment and risk of serious bronchospasm. If zanamivir is prescribed in such patients, closely monitor respiratory function. Special populations:

Effectiveness has not been established for prophylaxis of influenza in nursing home patients (per manufacturer). The CDC recommends zanamivir to be used to control institutional outbreaks of influenza when circulating strains are suspected of being resistant to oseltamivir (refer to current guidelines) (CDC 2011). Dosage form specific issues:

Powder for oral inhalation contains lactose; use contraindicated in patients allergic to milk proteins. Other warnings/precautions:

Relenza inhalation powder should only be administered via inhalation using the provided Diskhaler delivery device. The commercially available formulation is a lactose containing powder and is not intended to be solubilized or administered via any nebulizer/mechanical ventilator; inappropriate administration has resulted in death.

Antiviral treatment should begin within 48 hours of symptom onset. However, the CDC recommends that treatment may still be beneficial and should be started in hospitalized patients with severe, complicated or progressive illness if >48 hours. Treatment should not be delayed while awaiting results of laboratory tests for influenza (CDC 2015). Nonhospitalized persons who are not at high risk for developing severe or complicated illness and who have a mild disease are not likely to benefit if treatment is started >48 hours after symptom onset. Nonhospitalized persons who are already beginning to recover do not need treatment (CDC 2011). Safety and efficacy have not been established in patients with significant underlying medical conditions. Not a substitute for annual flu vaccination; has not been shown to reduce risk of transmission of influenza to others. Patients must be instructed in the use of the delivery system. Consider primary or concomitant bacterial infections. Safety and efficacy of repeated courses have not been established.