Dosing and uses of Relenza (zanamivir)
Adult dosage forms and strengths
inhalation powder
- 5mg (20 units per Rotadisk)
Influenza A & B, Prophylaxis
Household setting: 10 mg inhaled qDay for 10 days
Initiate within 36 hours of exposure
Community outbreaks: Begin within 5 days of outbreak; may administer for up to 28 days
Influenza A & B, Treatment
Start within 2 days of symptom onset; administer 2 doses on day 1, at least 2 hours apart
10 mg inhaled q12hr for 5 days; may consider longer treatment for patients severely ill after 5 days
Influenza H1N1 (Swine Flu) Prophylaxis (Off-label)
10 mg inhaled qDay for 10 days
Initiate within 7 days of exposure
Influenza H1N1 (Swine Flu) Treatment (Off-label)
Start within 2 days of symptom onset; administer 2 doses on day 1, at least 2 hours apart
10 mg inhaled q12hr for 5 days; may consider longer treatment for patients severely ill after 5 days
Pediatric dosage forms and strengths
inhalation powder
- 5mg (20 units per Rotadisk)
Influenza A & B, Prophylaxis
Household setting, >5 years: 10 mg inhaled qDay for 10 days; initiate within 48 hours of exposure
Community outbreak, 12-16 years: 10 mg inhaled qDay for 28 days; initiate within 5 days of outbreak
Influenza A & B, Treatment
>7 years: 10 mg inhaled q12hr for 5 days
Start within 2 days of symptom onset; administer 2 doses on day 1, at least 2 hours apart
Influenza H1N1 (Swine Flu) Prophylaxis (Off-label)
Household setting, >5 years old: 10 mg inhaled qDay for 10 days; initiate within 48 hours of exposure
Community outbreak, 12-16 years old: 10 mg inhaled qDay for 28 days; initiate within 5 days of outbreak
Influenza H1N1 (Swine Flu) Treatment (Off-label)
>7 years old: 10 mg inhaled q12hr for 5 days
Relenza (zanamivir) adverse (side) effects
>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
Warnings
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 and lactation
Pregnancy category: C
Prompt use of antiviral drugs during the 2009 H1N1 influenza pandemic improved survival among severely ill pregnant women; the CDC examined reports of severe flu (resulting in death or ICU admission) in 347 pregnant women during the pandemic; only 4 women (7%) of those who died received an antiviral within 2 days of symptom onset, compared with 41% of survivors. (MMWR Sept 9, 2011;60(35):1192-96
Lactation: unknown
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Relenza (zanamivir)
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)
