Zanamivir is an antiviral medication that acts as a neuraminidase inhibitor to treat and prevent influenza A and B virus infections by blocking viral release from host cells. Administered as a powder for inhalation, it works by inhibiting the neuraminidase enzyme, preventing the spread of the virus. Zanamivir is typically used for early symptom onset in adults and children and is particularly recommended for high-risk individuals.
BRAND NAMES
Relenza- available as a dry powder for inhalation, with each blister containing 5 mg of zanamivir.
MECHANISM OF ACTION
Zanamivir works by inhibiting the neuraminidase enzyme of the influenza virus, which is crucial for releasing new infectious viral particles from infected host cells. Zanamivir, acting as a sialic acid analog, attaches to the neuraminidase active site and inhibits its function of cleaving sialic acid residues. This inhibition prevents the virus from spreading to healthy cells, thereby reducing viral shedding, shortening the duration of infection, and lessening the severity of symptoms.
PHARMACOKINETICS
Absorption
Zanamivir is poorly absorbed orally, which is why it is delivered as a dry powder inhalant. Following inhalation, the drug accumulates in the respiratory tract, allowing it to directly target the influenza virus. A small amount of the dose is absorbed systemically, and the unabsorbed portion is excreted from the body.
Distribution
Zanamivir has a volume of distribution of approximately 16 L in adults.
Metabolism
Zanamivir undergoes virtually no metabolism and is eliminated mostly unchanged from the body. After inhalation, it has low systemic absorption, with unabsorbed drug excreted in the feces and the small absorbed portion cleared by the kidneys. This minimal hepatic metabolism reduces the potential for drug-drug interactions. For intravenous administration, the drug is predominantly cleared by the kidneys, necessitating dose adjustments for patients with renal impairment.
Excretion
The kidneys excrete approximately 90% of a zanamivir dose as the unchanged parent drug, as it is not metabolized by the body. The elimination rate is limited by absorption.
PHARMACODYNAMICS
Zanamivir is an antiviral medication that functions as a strong and selective inhibitor of influenza neuraminidase, an enzyme essential for the influenza virus to replicate. By inhibiting this enzyme, zanamivir prevents new virus particles from being released from infected cells and blocks the spread of the infection within the body.
ADMINISTRATION
Zanamivir, a powder for inhalation, is taken twice daily for five days to treat the flu, with doses spaced 12 hours apart and taken at the same times each day.
DOSAGE AND STRENGTH
Take this medication 10mg by oral inhalation, two times each day for five days as instructed.
• This medication is most effective when started within two days of symptom onset.
DRUG INTERACTIONS
Zanamivir, an inhaled antiviral medication for influenza, has a very low potential for drug interactions because it is poorly absorbed into the bloodstream. The only significant interaction is with the live attenuated influenza vaccine (LAIV), which should not be administered within two weeks before or 48 hours after starting zanamivir, as the antiviral may inhibit the vaccine's effectiveness. The flu shot can be administered at any point, whereas other vaccines must be given at specific times. If also using other inhaled medications, like a bronchodilator, it should be administered first. Patients with pre-existing respiratory conditions, such as asthma or COPD, should use zanamivir cautiously because of the potential risk of bronchospasm.
FOOD INTERACTIONS
Zanamivir (Relenza) has no known interactions with food or drinks, as it is an inhaled medication with minimal systemic absorption. The powder formulation does contain lactose, so it should not be used by individuals with a severe milk protein allergy. For specific concerns or if you have an underlying respiratory condition like asthma, you should consult a doctor.
CONTRAINDICATIONS
The main contraindications for zanamivir inhalation powder (Relenza) are a history of severe hypersensitivity reactions and the presence of underlying respiratory diseases like asthma or Chronic Obstructive Pulmonary Disease (COPD).
SIDE EFFECTS
- Respiratory: Nasal and throat irritation, pain in the throat or tonsils, and cough.
- Digestive: Nausea, vomiting, and diarrhea.
- Neurological: Headache and dizziness.
- General: Fever and chills.
- Severe breathing problems.
- Neuropsychiatric events.
- Severe allergic reactions.
OVER DOSE
- Breathing problems: Shortness of breath or wheezing.
- Dizziness or fainting.
- Nausea, vomiting, or diarrhea.
- Joint pain.
- Headache.
TOXICITY
Zanamivir has low systemic toxicity, but it poses specific risks for individuals with underlying respiratory disease due to the potential for severe bronchospasm. Most other side effects are mild to moderate and generally considered to be well-tolerated.
