Zanamivir

Trade Names:
Relenza
- Powder for oral inhalation 5 mg

Pharmacology

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Inhibition of influenza virus neuraminidase, with the possibility of alteration of virus particle aggregation and release.

Pharmacokinetics

Absorption

About 4% to 17% of orally inhaled dose is systemically absorbed. C _max is 17 to 142 ng/mL, and T _max is 1 to 2 h following a 10 mg dose. The AUC is 111 to 1,364 ng•h/mL.

Distribution

Less than 10% are protein bound.

Metabolism

No metabolites were detected in humans.

Elimination

Renally excreted as unchanged drug in urine. Serum t _½ is 2.5 to 5.1 h. Total Cl is 2.5 to 10.9 L/h. Unabsorbed drug is excreted in feces.

Special Populations

After IV administration, significant decrease in renal Cl and increase in t _½ (range, 3.1 to 18.5 h). Safety and efficacy have not been documented in severe renal function impairment.

Indications and Usage

Uncomplicated acute illness caused by influenza A and B virus in adults and children at least 7 yr of age who have been symptomatic for no longer than 2 days; prophylaxis of influenza in adults and children 5 yr of age and older.

Contraindications

Standard considerations.

Dosage and Administration

Oral inhalation 2 inhalations (one 5 mg blister per inhalation). Give twice daily (approximately 12 h apart) for 5 days.

Oral inhalation 2 inhalations (one 5 mg blister per inhalation) once daily for 10 days.

Oral inhalation 2 inhalations (one 5 mg blister per inhalation) once daily for 28 days.

General Advice

• For oral inhalation only. Not for intranasal inhalation.
• Initiate therapy within 48 h of onset of influenza symptoms.
• Administer doses at approximately the same time each day.

Storage/Stability

Store Diskhaler and blister packs at controlled room temperature (59° to 86°F). Do not puncture any blister until just before inhaling a dose.

Drug Interactions

None well documented.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Arrhythmias, syncope.

CNS

Dizziness, headache (2%).

Headache (13%); fatigue, malaise (5%).

Seizures.

Dermatologic

Facial edema, rash, including serious cutaneous reactions.

EENT

Ear, nose, throat infections (5%); nasal signs and symptoms (2%).

Nasal signs and symptoms (12%); throat and tonsil discomfort and pain (8%); nasal inflammation (1%).

GI

Diarrhea, nausea (3%); vomiting (1%).

Nausea, vomiting (1%).

Metabolic-Nutritional

Feeding problems, including decreased or increased appetite and anorexia (2%).

Musculoskeletal

Muscle pain (3%); arthralgia and articular rheumatism (2%).

Respiratory

Sinusitis (3%); bronchitis, cough (2%).

Viral respiratory infections (13%); cough (7%).

Bronchospasm, dyspnea.

Miscellaneous

Temperature regulation, including fever and chills (5%).

Allergic or allergic-like reactions, including oropharyngeal edema.

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Children

Safety and efficacy not established in children younger than 7 yr of age.

Safety and efficacy not established in children younger than 5 yr of age.

Bacterial infections

Not established for prophylactic use to prevent complications from serious bacterial infections that may begin with influenza-like symptoms.

Bronchospasm

Bronchospasm and decline in lung function have been reported. Discontinue use if this occurs.

High-risk patients

Safety and efficacy not demonstrated in patients with high-risk underlying medical conditions.

Underlying respiratory disease

Safety and efficacy not demonstrated in patients with underlying chronic pulmonary disease (severe COPD or asthma); use is not recommended.

Overdosage

Symptoms

No reports of overdosage. Doses up to 64 mg/day have been given by nebulizer and 1,200 mg/day for 5 days IV.

Patient Information

• Advise patient to read and carefully follow patient information leaflet before starting therapy.
• Review and demonstrate proper use of the delivery system.
• Caution parent or caregiver of child receiving zanamivir that medication should be used only under adult supervision and instruction. Review, and demonstrate if possible, proper use of the delivery system with supervising adult.
• Review dosing schedule and prescribed length of therapy with patient. Advise patient to inhale contents from 2 blisters twice daily for 5 days. Inform patient that 2 doses should be taken on the first day, provided there is at least 2 h between doses. On subsequent days, doses should be approximately 12 h apart at approximately the same time. Caution patient that medication must be started within 48 h of onset of influenza symptoms in order to be effective.
• Advise patient using an inhaled bronchodilator at the same time as zanamivir to use the inhaled bronchodilator before inhaling zanamivir.
• Advise patient that if a dose is missed to take as soon as remembered; however, if it is within 2 h of the time for the next dose, to skip the dose and take the next dose at the regularly scheduled time.
• Review other modalities for alleviating influenza symptoms (eg, rest, hydration, OTC antipyretics and analgesics).
• Remind patient to complete entire course of therapy, even if feeling better.
• Advise patient that medication does not reduce risk of transmission of flu virus to others, and to continue to take appropriate precautions to prevent spreading the infection.
• Advise patient that zanamivir is not a substitute for flu vaccination and to continue to obtain an annual flu vaccination.
• Advise patient to inform health care provider if flu symptoms do not appear to be improving or are worsening, or if new symptoms develop during or after treatment.
• Instruct patient to discontinue therapy and contact health care provider immediately if experiencing increased respiratory symptoms (eg, shortness of breath, worsening wheezing) or signs or symptoms of an allergic reaction (eg, hives, rash, swelling of throat).

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