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Zanamivir

Pronunciation: (zan-AM-i-veer)
Class: Antiviral agent

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% protein bound.

Metabolism

No metabolites were detected in humans.

Elimination

Renally excreted as unchanged drug in urine. Serum half-life 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

Renal Function Impairment

Renal Cl is decreased and the half-life is increased in patients with mild, moderate, or severe renal impairment. Safety and efficacy have not been documented in severe renal insufficiency. No dosage adjustments are needed. However, there is a potential for drug accumulation.

Hepatic Function Impairment

Pharmacokinetics have not been studied in patients with hepatic impairment.

Elderly

Pharmacokinetics have not been studied in patients older than 65 yr of age.

Gender

No differences in plasma concentrations or pharmacokinetics were observed between men and women.

Race

No differences in plasma concentrations or pharmacokinetics were observed based on race.

Indications and Usage

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

Unlabeled Uses

H1N1 Influenza A (Swine Flu)

For treatment and chemoprophylaxis of H1N1 influenza A (swine flu) virus infection. This includes patients with confirmed, probable, or suspected H1N1 influenza A (swine flu) virus infection and their close contacts. For more information, refer to the CDC guidelines at http://www.cdc.gov/h1n1flu/recommendations.htm .

Contraindications

Standard considerations.

Dosage and Administration

Influenza Treatment
Adults and Children 7 yr of age and older

Oral inhalation 2 inhalations (one 5 mg blister per inhalation) for 5 days. Two doses should be taken on the first day of treatment whenever possible, provided there is at least 2 h between doses. On subsequent days, doses should be about 12 h apart at approximately the same time each day.

Influenza Prophylaxis, Household Setting
Adults and children 5 yr of age and older

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

Influenza Prophylaxis Community Outbreak
Adults and adolescents

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

Off-Label Dosing
Prophylaxis of H1N1 Influenza A (Swine Flu) Adults

Oral inhalation Two 5 mg inhalations (10 mg total) once per day for 10 days as recommended by the CDC. Therapy should begin within 7 days of exposure. For more information, refer to the CDC guidelines at http://www.cdc.gov/h1n1flu/recommendations.htm .

Children 5 yr of age and older

Oral inhalation Two 5 mg inhalations (10 mg total) once per day for 10 days as recommended by the CDC. For more information, refer to the CDC guidelines at http://www.cdc.gov/h1n1flu/recommendations.htm .

Treatment of H1N1 Influenza A (Swine Flu) Adults

Oral inhalation Two 5 mg inhalations (10 mg total) twice per day for 5 days as recommended by the CDC. Treatment should begin within 2 days of onset of influenza symptoms. For more information, refer to the CDC guidelines at http://www.cdc.gov/h1n1flu/recommendations.htm .

Children 7 yr of age and older

Oral inhalation Two 5 mg inhalations (10 mg total) twice per day for 5 days as recommended by the CDC. For more information, refer to the CDC guidelines at http://www.cdc.gov/h1n1flu/recommendations.htm .

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

Live, attenuated influenza vaccine

Administer more than 2 wk before or 48 h after zanamivir.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Postmarketing

Arrhythmias, syncope.

CNS

Treatment

Dizziness, headache (2%).

Prophylaxis

Headache (24%); fatigue, malaise (8%).

Postmarketing

Delirium, including abnormal behavior; agitation; altered level of consciousness; anxiety; confusion; delusions; hallucinations; nightmares; seizures.

Dermatologic

Postmarketing

Facial edema, rash including serious cutaneous reactions.

EENT

Treatment

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

Prophylaxis

Throat and tonsil discomfort and pain (19%); nasal signs and symptoms (12%); ear, nose, and throat infections (2%); nasal inflammation (1%).

GI

Treatment

Diarrhea, nausea (3%); vomiting (2%).

Prophylaxis

Diarrhea, nausea, vomiting (2%).

Metabolic-Nutritional

Prophylaxis

Feeding problems including decreased or increased appetite and anorexia (4%).

Musculoskeletal

Prophylaxis

Muscle pain (8%); musculoskeletal pain (6%); arthralgia and articular rheumatism (2%).

Respiratory

Treatment

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

Prophylaxis

Cough (17%); viral respiratory infection (13%).

Postmarketing

Bronchospasm, dyspnea.

Miscellaneous

Prophylaxis

Temperature regulation disturbances including fever and/or chills (9%).

Postmarketing

Allergic or allergic-like reactions including oropharyngeal edema.

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Children

Influenza treatment

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

Influenza prophylaxis

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

Hypersensitivity

Allergic-like reactions, including oropharyngeal edema, serious skin rashes, and anaphylaxis, have been reported in postmarketing experience, including in patients sensitive to lactose (milk proteins).

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.

Neuropsychiatric events

Delirium and abnormal behavior leading to injury have been reported in postmarketing experience.

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.

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).