Zanamivir

Treatment of Influenza

Zanamivir® (Zanamivir) Inhalation Powder is indicated for treatment of uncomplicated acute illness due to influenza A and B virus in adults and pediatric patients aged 7 years and older who have been symptomatic for no more than 2 days.

Prophylaxis of Influenza

Zanamivir is indicated for prophylaxis of influenza in adults and pediatric patients aged 5 years and older.

Important Limitations on Use of Zanamivir

Zanamivir belongs to the family of medicines called antivirals, which are used to treat infections caused by viruses. Zanamivir is used in the treatment of the infection caused by the flu virus (influenza A and influenza B). Zanamivir may also be used to prevent and treat swine influenza A.

Zanamivir may reduce flu symptoms (weakness, headache, fever, cough, runny or stuffy nose, and sore throat) by 1 to 1.5 days. Zanamivir may also be used to prevent influenza infection if you have come into close contact with someone who has the flu.

Zanamivir must be started within 2 days of having flu symptoms. Zanamivir will not keep you from spreading the flu virus to other people. It may not work for everybody. Zanamivir may not be for you if you are severely sick or have a breathing problem (e.g., asthma or chronic obstructive pulmonary disease). If you receive the flu vaccine every year, continue to do so. Zanamivir is not a substitute for your yearly flu shot.

Zanamivir is available only with your doctor's prescription.

Usual Adult Dose for Influenza

10 mg (2 inhalations) inhaled orally twice a day (12 hours apart) for 5 days

If possible, 2 doses should be taken on the first day, provided there are at least 2 hours between the doses.

Usual Adult Dose for Influenza Prophylaxis

10 mg (2 inhalations) inhaled orally once a day

Duration:

Household setting: 10 days

Community outbreak: 28 days

Usual Pediatric Dose for Influenza

7 years or older: 10 mg (2 inhalations) inhaled orally twice a day (12 hours apart) for 5 days

If possible, 2 doses should be taken on the first day, provided there are at least 2 hours between the doses.

Usual Pediatric Dose for Influenza Prophylaxis

5 years or older: 10 mg (2 inhalations) inhaled orally once a day

Duration:

Household setting: 10 days

Community outbreak: 28 days

Renal Dose Adjustments

Safety and efficacy have not been established in the presence of severe renal insufficiency. Significant increases in Zanamivir half-life (6-fold compared to normal) and systemic exposure were observed following single intravenous doses of 2 mg or 4 mg in volunteers with severe renal impairment. However, since systemic absorption of orally inhaled Zanamivir is limited (4% to 17% of inhaled dose), the clinical significance of these findings is unknown.

Liver Dose Adjustments

Data not available

Precautions

Zanamivir is not recommended in patients with underlying airways disease such as asthma or chronic obstructive pulmonary disease. Serious cases of bronchospasm (including fatalities) have been reported during treatment with Zanamivir in patients with and without underlying airways disease. Zanamivir should be discontinued in any patient developing bronchospasm or decline in respiratory function; immediate treatment and hospitalization may be required. If Zanamivir use is considered for patients with underlying airways disease, the risks and benefits should be weighed. If it is prescribed, respiratory function should be carefully monitored and these patients should have a fast-acting inhaled bronchodilator readily available whenever Zanamivir is administered. The drug should be stopped and the physician notified in case of worsening respiratory symptoms. Patients scheduled to use an inhaled bronchodilator at the same time as the Zanamivir dose should use their bronchodilator before administering Zanamivir.

Zanamivir inhalation powder must not be made into an extemporaneous solution for administration by nebulization or mechanical ventilation. There have been reports of hospitalized patients with influenza who received a solution made with Zanamivir inhalation powder administered by nebulization or mechanical ventilation, including a fatal case where it was reported that the lactose in this formulation obstructed the proper functioning of the equipment. Zanamivir inhalation powder must only be administered by using the Diskhaler delivery device provided with the product.

Since efficacy of Zanamivir depends on prompt administration following onset of symptoms, it is essential that patients be instructed on the proper use of the Diskhaler delivery device, including a demonstration whenever possible.

Efficacy has not been established against infections other than those caused by influenza virus A and B. Zanamivir is not effective for the prevention of bacterial coinfections.

There are no data concerning the safety and efficacy of Zanamivir for the treatment of influenza when initiated more than 48 hours after the onset of symptoms. The effects of repeated treatment courses have also not been studied.

Zanamivir is contraindicated in patients with history of allergic reaction to milk proteins.

Allergic-like reactions, including anaphylaxis, oropharyngeal edema, and serious skin rashes have been reported. Zanamivir should be discontinued and the patient treated appropriately if an allergic reaction develops or is suspected.

Abnormal behavior and delirium leading to injury, with fatal outcomes in some cases, with the use of Zanamivir in influenza patients have been reported. Although frequency is unknown, based on Zanamivir usage, these events appear to be uncommon. These events were primarily reported in pediatric patients and often had an abrupt onset and rapid resolution. Since influenza may be associated with neurologic and behavioral symptoms (including seizures, hallucinations, delirium, and abnormal behavior, with fatal outcomes in some cases), Zanamivir's contribution to these events has not been established. Monitoring of patients with influenza for abnormal behavior during Zanamivir therapy is recommended. The risks and benefits of continuing therapy should be evaluated for each patient if neuropsychiatric symptoms occur.

Safety and efficacy have not been established in high-risk patients (e.g., asthma, chronic obstructive pulmonary disease, nursing home patients, severe or underlying medical conditions).

Influenza viruses change over time and the emergence of resistant or more virulent mutations may decrease the efficacy of Zanamivir. The available influenza drug susceptibility patterns and treatment effects should be considered when deciding whether to use Zanamivir.

Zanamivir may not reduce the risk of transmission of the influenza virus to others.

Safety and efficacy of Zanamivir for treatment and prophylaxis of influenza have not been established in pediatric patients less than 7 and 5 years of age, respectively.

Dialysis

Data not available

Other Comments

Zanamivir should be started within 48 hours after onset of symptoms.

Patients on inhaled bronchodilators should use the bronchodilator before Zanamivir if both are scheduled for use at the same time.

Zanamivir should not be considered a substitute for vaccination.

See also:
What is the most important information I should know about Zanamivir?

Zanamivir should not be used in place of getting a yearly flu shot. The Centers for Disease Control recommends an annual flu shot to help protect you each year from new strains of influenza virus.

Before using Zanamivir, tell your doctor if you have asthma, chronic obstructive pulmonary disease (COPD), or any other chronic lung condition. Serious or life-threatening bronchospasm (difficulty breathing) and other effects on the lungs can occur while using Zanamivir. Stop using Zanamivir and call your doctor at once if you have wheezing or severe breathing problems.

Do not use a nebulizer or ventilator to give Zanamivir. Zanamivir inhalation powder should never be mixed with a liquid.

Treatment with Zanamivir should start as soon as possible when flu symptoms appear, such as fever, chills, muscle aches, sore throat, and runny or stuffy nose.

Do not use this medication to treat flu symptoms in a child younger than 7 years old. Children as young as 5 years old may use the medication to prevent flu symptoms.

Do not use an inhaled nasal flu vaccine (FluMist) within 2 weeks before or 48 hours after using Zanamivir. Zanamivir may interfere with the drug action of FluMist, making the vaccine less effective. Follow your doctor's instructions.

Some people using Zanamivir have had rare side effects of confusion, delirium and self-injury. These symptoms have occurred most often in children. It is not known whether Zanamivir was the exact cause of these symptoms. However, anyone using Zanamivir should be watched closely for signs of confusion or unusual behavior. Call a doctor at once if you or the child using Zanamivir has any of these symptoms.

Use Zanamivir exactly as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Treatment with Zanamivir should start as soon as possible when flu symptoms appear, such as fever, chills, muscle aches, sore throat, and runny or stuffy nose.

Zanamivir is packaged in disk-shaped foil packs that contain 4 blisters of medicine. These disks are placed into a device called a DISKHALER that you will use to inhale the medicine. The device opens and loads a blister of inhalation powder each time you use the inhaler. The disk device is not to be used with a spacer. Follow the patient instructions provided with the DISKHALER.

Do not use a nebulizer or ventilator to give Zanamivir. Zanamivir inhalation powder should never be mixed with a liquid. Do not use any other medicines in the DISKHALER. Always put the cover back on the device when not in use.

To treat flu symptoms: Use 2 inhalations every 12 hours for 5 days. Your doctor may tell you to use two doses on the first day of treatment, spaced at least 2 hours apart. On the following days, the doses should be spaced 12 hours apart. Follow your doctor's instructions.

To prevent flu symptoms: Use 2 inhalations every 24 hours for 10 to 28 days. Follow your doctor's instructions.

If you have a chronic respiratory disease such as asthma or COPD and you are scheduled to use an inhaled bronchodilator at the same time as Zanamivir, use the inhaled bronchodilator before using this medicine.

Use this medication for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Tell your doctor if your symptoms do not improve, or if they get worse.

Store Zanamivir at room temperature away from moisture and heat. Throw away the DISKHALER after your treatment ends.

Zanamivir is used to treat symptoms caused by the flu virus (influenza) if you have had symptoms for 2 days or less. It helps lessen symptoms (such as stuffy nose, cough, sore throat, fever/chills, headache, body aches, tiredness) and shortens the recovery time by about 1 to 2 days.

Zanamivir may also be used to prevent the flu if you have been exposed to someone who already has the flu (such as a sick household member) or if there is a flu outbreak in the community. Talk to your doctor for more details.

This medication works by stopping the flu virus from growing. It is not a substitute for the flu vaccine.

If you have the flu, Zanamivir does not reduce the risk of giving the flu to others.

How to use Zanamivir inhalation

Read the Patient Information Leaflet provided by your pharmacist before you start using Zanamivir and each time you get a refill. Learn all usage instructions. If you have any questions, ask your doctor or pharmacist.

For flu treatment: inhale this medication through your mouth as directed by your doctor, usually 2 inhalations (1 blister per inhalation) twice a day (about 12 hours apart) for 5 days. If possible, on the first day of treatment, take two doses (2 inhalations each), waiting at least 2 hours between doses.

For flu prevention: inhale this medication through your mouth as directed by your doctor, usually 2 inhalations (1 blister per inhalation) once a day. The usual length of time you will take Zanamivir is 10 days if there is a sick household member or 28 days if there is a flu outbreak in the community, or as directed by your doctor.

Remove the cover on the disk inhaler. Before use, check the mouthpiece to be sure it is clean and free of particles. Load the medication disk into the disk inhaler. Puncture one medication blister. Keep the disk inhaler level so that the medication will not spill out. Breathe out all the way through your mouth, put the mouthpiece into your mouth, and breathe in through your mouth as deeply as you can. This will draw the medication into your lungs. Hold your breath for a few seconds. To take another inhalation, advance to the next medication blister and repeat the process. Replace the cover of the disk inhaler.

Do not mix this powder medication with any liquids, including nebulizer liquids.

If a child is using this medication, a parent or other responsible adult should supervise the child to make sure it is used properly.

Start Zanamivir as soon as possible. This medication works best when the amount of medicine in your body is kept at a constant level. Therefore, use this drug at evenly spaced intervals at the same time(s) every day.

Continue to use this medication for the full time prescribed, even if symptoms improve. Stopping the medication too early may result in a return of the infection, or failure to protect you from the flu.

If you have breathing problems (such as asthma, chronic obstructive pulmonary disease-COPD) and are scheduled to use inhaled bronchodilators (such as albuterol) at the same time as Zanamivir, use the bronchodilator medication before using Zanamivir. Ask your doctor or pharmacist for more details.

Tell your doctor if your condition persists or worsens or if new symptoms appear.

See also:
What other drugs will affect Zanamivir?

Zanamivir is not a substrate nor does it affect cytochrome P450 (CYP) isoenzymes (CYP1A1/2, 2A6, 2C9, 2C18, 2D6, 2E1, and 3A4) in human liver microsomes. No clinically significant pharmacokinetic drug interactions are predicted based on data from in vitro studies.

The concurrent use of Zanamivir with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of potential interference between these products, LAIV should not be administered within 2 weeks before or 48 hours after administration of Zanamivir, unless medically indicated. The concern about possible interference arises from the potential for antiviral drugs to inhibit replication of live vaccine virus.

Trivalent inactivated influenza vaccine can be administered at any time relative to use of Zanamivir.

See also:
What are the possible side effects of Zanamivir?

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The placebo used in clinical trials consisted of inhaled lactose powder, which is also the vehicle for the active drug; therefore, some adverse events occurring at similar frequencies in different treatment groups could be related to lactose vehicle inhalation.

Treatment of Influenza

Clinical Trials in Adults and Adolescents: Adverse events that occurred with an incidence ≥ 1.5% in treatment trials are listed in Table 1. This table shows adverse events occurring in subjects aged 12 years and older receiving Zanamivir 10 mg inhaled twice daily, Zanamivir in all inhalation regimens, and placebo inhaled twice daily (where placebo consisted of the same lactose vehicle used in Zanamivir).

Table 1: Summary of Adverse Events ≥ 1.5% Incidence During Treatment in Adults and Adolescents

Postmarketing Experience

In addition to adverse events reported from clinical trials, the following events have been identified during postmarketing use of Zanamivir. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to Zanamivir.

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 have been reported shortly following inhalation of Zanamivir.

Respiratory: Bronchospasm, dyspnea.

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

Each pre-dispensed quantity of inhalation powder (one blister) contains 5 mg Zanamivir. Each delivered inhalation (the amount that leaves the mouthpiece of the Diskhaler) contains 4.0 mg Zanamivir.

Excipients/Inactive Ingredients: Lactose monohydrate (approximately 20 mg which contains milk protein).