zanamivir (Rx)

>10%

Headache (13-24%)

Throat/tonsil pain (8-19%)

Cough ( 7-17%)

Viral infection (3-13%)

>1%

Dizziness (2%)

Nausea (3%)

Diarrhea (3% adults, 2% children)

Vomiting (1% adults, 2% children)

Sinusitis (3%)

Bronchitis (2%)

Infection (ear, nose, & throat; 2% adults, 5% children)

<1%

Malaise

Fatigue

Fever

Abdominal pain

Myalgia

Arthralgia

Urticaria

Postmarketing Reports

Allergic Reactions: Allergic or allergic-like reaction, including oropharyngeal edema

Psychiatric: Delirium, including symptoms such as altered level of consciousness, confusion, abnormal behavior, delusions, hallucinations, agitation, anxiety, nightmares

Cardiac: Arrhythmias, syncope.

Neurologic: Seizures, vasovagal-like episodes shortly after administration

Respiratory: Bronchospasm, dyspnea

Skin: Facial edema; rash, including serious cutaneous reactions (eg, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis); urticaria

Contraindications

Hypersensitivity to zanamivir or formulation, including milk proteins

Cautions

Administer only via the Diskhaler inhaler

Do not make into an extemporaneous solution for administration by nebulization or mechanical ventilation; fatality reports of hospitalized patients with influenza who received a solution made with Relenza Inhalation Powder administered by nebulization or mechanical ventilation; lactose in this formulation obstructs proper functioning of the equipment

Most effective when used within 24-48 hr of onset of symptoms

Not recommended for treatment or prophylaxis of influenza in individuals with underlying airway diseases (eg, asthma, COPD); serious cases of bronchospasm, including fatalities, have been reported during treatment

If use is considered for patient with underlying airway disease, carefully monitor respiratory function, closely observe patient, and have supportive therapy (ie, fast-acting bronchodilators) immediately available

Reports of abnormal behavior and delirium

Pregnancy

Available data from published studies suggest that use during pregnancy is not associated with an increased risk of birth defects or adverse maternal or fetal outcomes; however, these studies are limited by their small sample sizes, which preclude a definitive assessment of the risk; there are risks to mother and fetus associated with influenza infection in pregnancy; in animal reproduction studies, no adverse developmental effects were observed with intravenous or subcutaneous administration of zanamivir at exposures 300 and 150 times, respectively, the systemic exposure at the maximum recommended human inhalation dose (MRHID) of 10 mg twice daily

Pregnant women are at higher risk of severe complications from influenza, which may lead to adverse pregnancy and/or fetal outcomes, including maternal death, stillbirths, birth defects, preterm delivery, low birth weight,and small for gestational age

Lactation

There are no data on presence of zanamivir in human milk or effects on milk production; there are data from adults that have shown low oral bioavailability of zanamivir; limited data from postmarketing case reports have not suggested a safety concern in infants exposed to breast milk of mothers receiving therapy; drug was present in milk of lactating rats without effect on nursing pups; developmental and health benefits of breastfeeding should be considered along with mother’s clinical need for therapy and any potential adverse effects on breastfed child from drug or underlying maternal condition

Mechanism of Action

Inhibits viral neuraminidases; stops release of virus from cells & prevents virus from crossing mucous lining of respiratory tract

Pharmacokinetics

Absorption: Inhalation: 4-17%

Protein binding: <10%

Metabolism: None

Half-life: 2.5-5.1 hr

Excretion: Urine (as unchanged drug); feces (unabsorbed drug)