Zanamivir Dosage

Usual Adult Dose for Influenza

10 mg (2 inhalations) inhaled orally twice a day (12 hours apart) for 5 days

If possible, 2 doses should be taken on the first day, provided there are at least 2 hours between the doses.

Usual Adult Dose for Influenza Prophylaxis

10 mg (2 inhalations) inhaled orally once a day

Duration:
Household setting: 10 days
Community outbreak: 28 days

Usual Pediatric Dose for Influenza

7 years or older: 10 mg (2 inhalations) inhaled orally twice a day (12 hours apart) for 5 days

If possible, 2 doses should be taken on the first day, provided there are at least 2 hours between the doses.

Usual Pediatric Dose for Influenza Prophylaxis

5 years or older: 10 mg (2 inhalations) inhaled orally once a day

Duration:
Household setting: 10 days
Community outbreak: 28 days

Renal Dose Adjustments

Safety and efficacy have not been established in the presence of severe renal insufficiency. Significant increases in zanamivir half-life (6-fold compared to normal) and systemic exposure were observed following single intravenous doses of 2 mg or 4 mg in volunteers with severe renal impairment. However, since systemic absorption of orally inhaled zanamivir is limited (4% to 17% of inhaled dose), the clinical significance of these findings is unknown.

Liver Dose Adjustments

Data not available

Precautions

Zanamivir is not recommended in patients with underlying airways disease such as asthma or chronic obstructive pulmonary disease. Serious cases of bronchospasm (including fatalities) have been reported during treatment with zanamivir in patients with and without underlying airways disease. Zanamivir should be discontinued in any patient developing bronchospasm or decline in respiratory function; immediate treatment and hospitalization may be required. If zanamivir use is considered for patients with underlying airways disease, the risks and benefits should be weighed. If it is prescribed, respiratory function should be carefully monitored and these patients should have a fast-acting inhaled bronchodilator readily available whenever zanamivir is administered. The drug should be stopped and the physician notified in case of worsening respiratory symptoms. Patients scheduled to use an inhaled bronchodilator at the same time as the zanamivir dose should use their bronchodilator before administering zanamivir.

Zanamivir inhalation powder must not be made into an extemporaneous solution for administration by nebulization or mechanical ventilation. There have been reports of hospitalized patients with influenza who received a solution made with zanamivir inhalation powder administered by nebulization or mechanical ventilation, including a fatal case where it was reported that the lactose in this formulation obstructed the proper functioning of the equipment. Zanamivir inhalation powder must only be administered by using the Diskhaler delivery device provided with the product.

Since efficacy of zanamivir depends on prompt administration following onset of symptoms, it is essential that patients be instructed on the proper use of the Diskhaler delivery device, including a demonstration whenever possible.

Efficacy has not been established against infections other than those caused by influenza virus A and B. Zanamivir is not effective for the prevention of bacterial coinfections.

There are no data concerning the safety and efficacy of zanamivir for the treatment of influenza when initiated more than 48 hours after the onset of symptoms. The effects of repeated treatment courses have also not been studied.

Zanamivir is contraindicated in patients with history of allergic reaction to milk proteins.

Allergic-like reactions, including anaphylaxis, oropharyngeal edema, and serious skin rashes have been reported. Zanamivir should be discontinued and the patient treated appropriately if an allergic reaction develops or is suspected.

Abnormal behavior and delirium leading to injury, with fatal outcomes in some cases, with the use of zanamivir in influenza patients have been reported. Although frequency is unknown, based on zanamivir usage, these events appear to be uncommon. These events were primarily reported in pediatric patients and often had an abrupt onset and rapid resolution. Since influenza may be associated with neurologic and behavioral symptoms (including seizures, hallucinations, delirium, and abnormal behavior, with fatal outcomes in some cases), zanamivir's contribution to these events has not been established. Monitoring of patients with influenza for abnormal behavior during zanamivir therapy is recommended. The risks and benefits of continuing therapy should be evaluated for each patient if neuropsychiatric symptoms occur.

Safety and efficacy have not been established in high-risk patients (e.g., asthma, chronic obstructive pulmonary disease, nursing home patients, severe or underlying medical conditions).

Influenza viruses change over time and the emergence of resistant or more virulent mutations may decrease the efficacy of zanamivir. The available influenza drug susceptibility patterns and treatment effects should be considered when deciding whether to use zanamivir.

Zanamivir may not reduce the risk of transmission of the influenza virus to others.

Safety and efficacy of zanamivir for treatment and prophylaxis of influenza have not been established in pediatric patients less than 7 and 5 years of age, respectively.

Dialysis

Data not available

Other Comments

Zanamivir should be started within 48 hours after onset of symptoms.

Patients on inhaled bronchodilators should use the bronchodilator before zanamivir if both are scheduled for use at the same time.

Zanamivir should not be considered a substitute for vaccination.