Zanamivir

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Aerosol Powder Breath Activated, Inhalation:

Relenza Diskhaler: 5 mg/blister (20 ea) [contains lactose]

Pharmacology

Mechanism of Action

Zanamivir inhibits influenza virus neuraminidase enzymes, potentially altering virus particle aggregation and release.

Pharmacokinetics/Pharmacodynamics

Absorption

Inhalation: Systemic: ~4% to 17%

Distribution

V_d: ~16 L

Metabolism

None

Excretion

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

Time to Peak

1-2 hours

Half-Life Elimination

Serum: 2.5 to 5.1 hours

Protein Binding

Plasma: <10%

Use in Specific Populations

Special Populations: Renal Function Impairment

Systemic exposure is increased after an IV dose.

Use: Labeled Indications

Influenza:

Prophylaxis: Prophylaxis of influenza in adults and pediatric patients 5 years and older.

Treatment: Treatment of uncomplicated acute illness caused by influenza A and B virus in adults and pediatric patients 7 years and older who have been symptomatic for no more than 2 days.

The Advisory Committee on Immunization Practices (ACIP) recommends that treatment be considered for the following:

• Persons with severe, complicated or progressive illness
• Hospitalized persons
• Persons at higher risk for influenza complications:

- Children <2 years of age (highest risk in children <6 months of age)

- Adults ≥65 years of age

- Persons with chronic disorders of the pulmonary (including asthma) or cardiovascular systems (except hypertension)

- Persons with chronic metabolic diseases (including diabetes mellitus), hepatic disease, renal dysfunction, hematologic disorders (including sickle cell disease), or immunosuppression (including immunosuppression caused by medications or HIV)

- Persons with neurologic/neuromuscular conditions (including conditions such as spinal cord injuries, seizure disorders, cerebral palsy, stroke, mental retardation, moderate to severe developmental delay, or muscular dystrophy) which may compromise respiratory function, the handling of respiratory secretions, or that can increase the risk of aspiration

- Pregnant or postpartum women (≤2 weeks after delivery)

- Persons <19 years of age on long-term aspirin therapy

- American Indians and Alaskan Natives

- Persons who are morbidly obese (BMI ≥40)

- Residents of nursing homes or other chronic care facilities

• Use may also be considered for previously healthy, nonhigh-risk outpatients with confirmed or suspected influenza based on clinical judgment when treatment can be started within 48 hours of illness onset.

The ACIP recommends that prophylaxis be considered for the following:

• Postexposure prophylaxis may be considered for family or close contacts of suspected or confirmed cases, who are at higher risk of influenza complications, and who have not been vaccinated against the circulating strain at the time of the exposure.
• Postexposure prophylaxis may be considered for unvaccinated healthcare workers who had occupational exposure without protective equipment.
• Pre-exposure prophylaxis should only be used for persons at very high risk of influenza complications who cannot be otherwise protected at times of high risk for exposure.
• Prophylaxis should also be administered to all eligible residents of institutions that house patients at high risk when needed to control outbreaks.

Contraindications

Hypersensitivity to zanamivir or any component of the formulation (contains milk proteins)

Dosage and Administration

Dosing: Adult

Influenza: Oral inhalation:

Prophylaxis (household exposure): Two inhalations (10 mg) once daily for 7 days after last known exposure (CDC 2015)

Prophylaxis (institutional outbreak): Two inhalations (10 mg) once daily; continue for ≥2 weeks and until ~7 days after identification of illness onset in the last patient (CDC 2015). Zanamivir is to be used to control institutional outbreaks of influenza when circulating strains are suspected of being resistant to oseltamivir (CDC 2011).

Prophylaxis (community outbreak): Two inhalations (10 mg) once daily; continue until influenza activity in community subsides or immunity obtained from immunization; up to 28 days has been well tolerated (CDC 2011; CDC 2015)

Treatment: Two inhalations (10 mg) twice daily for 5 days. Doses on first day should be separated by at least 2 hours; on subsequent days, doses should be spaced by ~12 hours. Begin within 2 days of signs or symptoms. Longer treatment may be considered for patients who remain severely ill after 5 days (CDC 2015).

Missed dose: If a dose is missed, administer as soon as possible unless it is ≤2 hours before the next scheduled dose. Then, continue administration at the previous schedule; do not administer a double dose.

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Note: 10 mg dose is provided by 2 inhalations (one 5 mg blister per inhalation):

Influenza virus A and B; treatment: Oral inhalation: Children ≥7 years and Adolescents: Two inhalations (10 mg) twice daily for 5 days; doses on first day should be separated by at least 2 hours; on subsequent days, doses should be spaced by ~12 hours. Begin within 2 days of signs or symptoms. Longer treatment may be considered for patients who remain severely ill after 5 days.

Influenza virus A and B; prophylaxis: Oral inhalation:

Manufacturer's labeling:

Household setting: Children ≥5 years and Adolescents: Two inhalations (10 mg) once daily for 10 days; begin within 36 hours following onset of signs or symptoms of index case

Community outbreak: Adolescents: Two inhalations (10 mg) once daily for 28 days; begin within 5 days of outbreak

Alternate dosing: Children ≥5 years and Adolescents:

Household setting: CDC Recommendation: Two inhalations (10 mg) once daily for 7 days after last known exposure (CDC, 2012)

Community outbreak: IDSA/PIDS recommendations: Two inhalations (10 mg) once daily; continue until influenza activity in community subsides or immunity obtained from immunization; up to 28 days has been well tolerated (Bradley, 2011; CDC, 2011)

Institutional outbreak: CDC recommendations: Two inhalations (10 mg) once daily; continue for ≥2 weeks and until ~7 days after identification of illness onset in the last patient. Zanamivir is to be used to control institutional outbreaks of influenza when circulating strains are suspected of being resistant to oseltamivir (CDC, 2012).

HIV-exposed/-positive: Two inhalations (10 mg) once daily for 10 days after last known exposure (DHHS [pediatric], 2013)

Administration

Oral inhalation: Must be used with Diskhaler delivery device. The foil blister disk containing zanamivir inhalation powder should not be manipulated, solubilized, or administered via a nebulizer. Patients scheduled to use an inhaled bronchodilator at the same time as zanamivir should use their bronchodilator prior to zanamivir. With the exception of the initial dose when used for treatment, administer at approximately the same time each day.

Storage

Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F). Do not puncture blister until taking a dose using the Diskhaler.

Drug Interactions

Influenza Virus Vaccine (Live/Attenuated): Antiviral Agents (Influenza A and B) may diminish the therapeutic effect of Influenza Virus Vaccine (Live/Attenuated). Management: Avoid anti-influenza antivirals during the period beginning 48 hours prior to and ending 2 weeks after live influenza virus vaccine administration. Consider therapy modification

Adverse Reactions

Most adverse reactions occurred at a frequency that was less than or equal to the control (lactose vehicle).

>10%:

Central nervous system: Headache (prophylaxis: 13% to 24%; treatment: 2%)

Gastrointestinal: Sore throat (or discomfort; prophylaxis: ≤19%)

Infection: Viral infection (prophylaxis: 3% to 13%)

Respiratory: Nasal signs and symptoms (prophylaxis: 12% to 20%; treatment: 2%), tonsil disease (discomfort or pain; prophylaxis: ≤19%), cough (prophylaxis: 7% to 17%; treatment: ≤2%)

1% to 10%:

Central nervous system: Chills (prophylaxis: ≤9%; treatment: <2%), fatigue (prophylaxis: 5% to 8%; treatment: <2%), malaise (prophylaxis: 5% to 8%; treatment: <2%), dizziness (treatment: 1% to 2%)

Dermatologic: Urticaria (treatment: <2%)

Gastrointestinal: Anorexia (prophylaxis: ≤4%), decreased appetite (prophylaxis: ≤4%), increased appetite (prophylaxis: 2% to 4%), nausea (prophylaxis: 1% to 2%; treatment: ≤3%), diarrhea (2% to 3%), vomiting (1% to 2%), abdominal pain (treatment: <2%)

Neuromuscular & skeletal: Myalgia (prophylaxis: 3% to 8%; treatment: <2%), musculoskeletal pain (prophylaxis: 6%), arthralgia (≤2%), rheumatic disease (prophylaxis: ≤2%)

Respiratory: ENT infection (treatment: 1% to 5%; prophylaxis: 2%), sinusitis (treatment: 3%), bronchitis (treatment: 2%), rhinitis (prophylaxis: 1%)

Miscellaneous: Fever (prophylaxis: ≤9%; treatment: <2%)

<1%, postmarketing and/or case reports: Abnormal behavior, agitation, anxiety, asthma, bronchospasm, cardiac arrhythmia, delusions, dyspnea, facial edema, hallucination, hemorrhage (ear/nose/throat), hypersensitivity reaction (or hypersensitivity-like reaction; includes oropharyngeal edema), impaired consciousness, nightmares, psychiatric disturbance (confusion, delirium, self-injury), seizure, skin rash (including serious cutaneous reactions [eg, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis]), syncope

Warnings/Precautions

Concerns related to adverse effects:

• Allergic reactions: Allergic-like reactions, including anaphylaxis, oropharyngeal edema, and serious skin rashes have been reported. Discontinue use and institute appropriate treatment if an allergic reaction occurs.
• Neuropsychiatric events: 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.
• Respiratory effects: 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:

• Respiratory disease: 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.

Concurrent drug therapy issues:

• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Special populations:

• Nursing home patients: 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:

• Lactose: Powder for oral inhalation contains lactose; use contraindicated in patients allergic to milk proteins.

Other warnings/precautions:

• Administration: 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.
• Appropriate use: 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.

Pregnancy

Pregnancy Considerations

An increased risk of adverse neonatal or maternal outcomes has not been observed following use of zanamivir during pregnancy (CDC 60[1] 2011).

Untreated influenza infection is associated with an increased risk of adverse events to the fetus and an increased risk of complications or death to the mother. Although neuraminidase inhibitors are currently recommended for the treatment or prophylaxis of influenza in pregnant women and women up to 2 weeks' postpartum, zanamivir is not the preferred agent (ACOG 2018; CDC 60[1] 2011).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
• Patient may experience headache, diarrhea, nausea, vomiting, stuffy nose, sore throat, cough, or dizziness. Have patient report immediately to prescriber shortness of breath, difficulty breathing, chest pain, signs of ear, nose, or throat infection, behavioral changes, confusion, difficulty speaking, tremors, seizures, or sensing things that seem real but are not (HCAHPS).
• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.