Zanamivir

Treatment of Influenza

Zanamivir is used to treat uncomplicated illness caused by influenza A and B viruses. It is intended for adults and children 7 years of age and older who have experienced flu symptoms for no more than 48 hours. When taken promptly, it can help reduce the severity of symptoms and shorten the time it takes to recover.

Prevention of Influenza

This medication is also used to prevent the flu in adults and children 5 years of age and older. It may be prescribed in specific situations, such as:

• When a person has been in close contact with someone who has the flu, such as a member of the same household.
• During a community outbreak to provide protection for those at risk of infection.

Important Considerations

Zanamivir is specifically designed to target influenza viruses and is not effective against the common cold or other types of viral or bacterial infections. It is not a substitute for the annual flu vaccine. Health experts recommend receiving a flu shot every year as the primary method for preventing influenza.

Mechanism of Action

Zanamivir belongs to a class of drugs known as neuraminidase inhibitors. It is specifically designed to target the influenza virus, which causes the flu, by interfering with its ability to replicate and spread within the respiratory system.

When a person is infected with the flu, the virus enters cells in the body and uses them to create new virus particles. To spread the infection, these new particles must break away from the infected cell to attack healthy ones. The virus uses a specific enzyme on its surface called neuraminidase to act like a chemical tool to cut itself loose.

Zanamivir works by:

• Binding to the neuraminidase enzyme on the surface of the virus.
• Blocking the enzyme's ability to release new virus particles from infected cells.
• Trapping the virus within the cells it has already infected.

By preventing the virus from spreading to new cells, the medication helps limit the severity of the infection. This allows the body's natural immune system to clear the virus more effectively, which can shorten the duration of flu symptoms and help prevent the virus from developing in people who have been exposed to it.

This medication is effective against both influenza A and influenza B viruses. It is most effective when started as soon as possible after symptoms appear, as this is the period when the virus is most active in the body.

Common Side Effects

The following side effects are generally mild and may go away as your body adjusts to the medication:

• Headache
• Dizziness
• Nausea or vomiting
• Diarrhea
• Cough or sore throat
• Sinus pain or nasal congestion
• Ear pain
• Fever or chills
• Joint pain

Serious Side Effects

Seek medical attention immediately if you experience any of the following serious symptoms:

• Breathing problems: Wheezing, chest tightness, or sudden difficulty breathing. This risk is significantly higher for individuals with underlying lung diseases such as asthma or chronic obstructive pulmonary disease (COPD).
• Allergic reactions: Severe skin rash, hives, or swelling of the face, lips, or tongue.
• Neuropsychiatric symptoms: Confusion, agitation, hallucinations, delirium, or unusual behavior. These symptoms have been reported primarily in children and teenagers with the flu.
• Fainting: Feeling lightheaded or passing out shortly after using the inhaler.

Respiratory Warnings

Zanamivir can cause serious breathing problems, including bronchospasm (narrowing of the airways). This medication is not recommended for people with underlying respiratory diseases such as asthma or chronic obstructive pulmonary disease (COPD). If wheezing or difficulty breathing occurs, the medication should be stopped immediately and medical attention sought. Individuals with respiratory disease who must use zanamivir should have a fast-acting inhaled bronchodilator available.

Neuropsychiatric Events

Some patients, particularly children and adolescents, have experienced unusual behavior changes while taking zanamivir. These events may include:

• Delirium
• Hallucinations
• Confusion
• Self-injury

These symptoms often have an abrupt onset. Patients should be monitored closely for signs of abnormal behavior throughout the treatment period.

Allergic Reactions

Serious allergic reactions have been reported, including anaphylaxis and severe skin reactions. Zanamivir inhalation powder contains lactose, which may contain milk proteins. It should not be used by individuals with a known severe milk protein allergy or hypersensitivity to any of the ingredients.

Other Considerations

Zanamivir is not a substitute for the annual influenza vaccine. Additionally, it is only effective against viral infections; it does not treat bacterial infections that may occur as complications of the flu. If a patient's condition worsens or new symptoms develop, further medical evaluation is necessary to rule out bacterial causes.

Pregnancy

The effects of zanamivir on an unborn baby are not well-studied, and it is currently unknown if the medication can cause harm during pregnancy. However, healthcare providers often consider that the flu itself poses a significant risk to pregnant individuals. Severe flu symptoms during pregnancy can lead to serious health complications for both the parent and the baby, including premature labor.

If you are pregnant or planning to become pregnant, discuss the potential risks and benefits with your doctor. They will determine if treatment is necessary based on your specific health needs and the severity of the flu symptoms.

Breastfeeding

It is not known if zanamivir passes into human breast milk or how it might affect a nursing infant. Because there is limited information available, it is important to consult a healthcare provider before using this medication while breastfeeding to ensure the safety of the baby.

Available Forms

Zanamivir is supplied as a dry powder for oral inhalation. The powder is contained within individual blisters on a circular foil disk.

This medication is administered using a specially designed inhalation device. It is not available as a pill, liquid, or injection, and it should not be used in a standard nebulizer machine.

FDA Approval and Indications

Zanamivir was approved by the U.S. Food and Drug Administration (FDA) in 1999. It is indicated for the following uses:

• Treatment: For the treatment of uncomplicated acute illness caused by influenza A and B virus in adults and pediatric patients 7 years of age and older who have been symptomatic for no more than two days.
• Prevention: For the prophylaxis of influenza in adults and pediatric patients 5 years of age and older.

Regulatory Warnings

While zanamivir does not carry a boxed warning, the FDA-approved labeling includes significant precautions regarding its use in patients with underlying respiratory diseases. There have been reports of serious bronchospasm, including fatalities, in patients with asthma or chronic obstructive pulmonary disease (COPD) who used zanamivir. Consequently, it is not recommended for treatment or prophylaxis of influenza in individuals with underlying airway disease.

Limitations of Use

Zanamivir is not a substitute for annual flu vaccination. The FDA notes that its effectiveness has not been established for patients with certain high-risk underlying medical conditions or for the treatment of influenza in patients with very severe or complicated illness requiring hospitalization.

Using the Inhalation Device

Zanamivir is not swallowed as a pill; instead, it is inhaled through the mouth using a device called a Diskhaler. The medication comes in circular foil blister packs known as Rotadisks, which are loaded into the device. Each blister contains a single dose of the dry powder medication.

Proper Administration

• Preparation: The foil blister must be punctured by the device before inhalation.
• Technique: To use the inhaler, you must breathe out fully (away from the device), place the mouthpiece in your mouth, and breathe in quickly and deeply.
• Breath Holding: After inhaling the powder, you should hold your breath for several seconds to allow the medication to reach the lungs.

It is important to only use the Diskhaler provided with the medication. This drug should not be mixed with water or used in a nebulizer or ventilator.

Respiratory Precautions

Because the medication is inhaled, it can cause the airways to tighten (bronchospasm), especially in people with underlying lung conditions. Zanamivir is generally not recommended for individuals with asthma or chronic obstructive pulmonary disease (COPD). If you use other inhaled medications, such as bronchodilators, for asthma, you should have them available while using zanamivir.