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Relenza (zanamivir)

What is Relenza?

Relenza (zanamivir) is another solid option to treat the influenza virus. With the active element zanamivir, Relenza is taken orally and can handle several kinds of flu. If you have tried other options and those failed, Relenza comes as a perfect alternative when all other options failed. This medicine is usually prescribed to someone at risk of developing flu complications; these include people with diabetes, lung and heart patients or elderly people. Although Relenza is a good solid medicine it should not be considered as a substitute for the vaccine against the seasonal flu.

       Treatment Dosage Quantity Per Inhaler Price Buy now
Relenza Relenza 5mg 5 £14.34 £71.70 Buy Now

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Buy Relenza With an Online Prescription

An online doctor consultation means filling out a medical questionnaire. A registered EU doctor assesses your medical questionnaire and analize whether Relenza is suitable and safe for you to buy. After approval, a prescription is issued and send to the registered EU pharmacy. You will receive your discretely shipped Relenza pills within 3 business days.

Pharmacologic effect

Zanamivir is a highly active and highly selective inhibitor of neuraminidase (a surface enzyme of the influenza virus ). Viral neuraminidase provides the release of newly formed virus particles from infected cells and can accelerate the penetration of the virus through the mucous barrier to the surface of epithelial cells, thereby causing infection of other cells. The inhibitory activity of zanamivir with respect to the replication of influenza viruses of type A and B is shown both in vitro and in vivo and includes all known subtypes of neuraminidase of influenza type A viruses.

Influenza virus replication is limited to surface airway epithelial cells. Zanamivir acts in the extracellular space and reduces the reproduction of both types of influenza virus (A and B), preventing the release of infectious viral particles from the epithelial cells of the respiratory tract. The effectiveness of zanamivir for inhalation is confirmed by clinical studies.

Clinical data show that the use of zanamivir for the treatment of acute infections caused by influenza virus leads to a decrease in the release of the virus from the respiratory tract compared with the placebo group, while the appearance of strains with reduced susceptibility to zanamivir was not detected.



Pharmacokinetic studies in humans have shown that the absolute bioavailability of zanamivir after oral administration is low and averages 2%. Similar studies of zanamivir after oral inhalation indicate that from 10% to 20% of the administered dose undergoes systemic absorption, and Cmax in plasma is usually achieved within 1 to 2 hours after administration. A low degree of absorption of the drug leads to low systemic concentrations, i.e. zanamivir after oral inhalation does not have a significant systemic effect. There is no evidence of a change in the pharmacokinetics of the drug after repeated oral inhalations.


The binding of zanamivir to plasma proteins is very low (<10%). V d of zanamivir in adults is about 16 L, which approximately corresponds to the volume of extracellular fluid.

After oral inhalation, zanamivir is deposited throughout the respiratory tract in high concentrations, ensuring delivery of the drug to the site of infection. After a single inhalation of 10 mg of zanamivir, the concentration of the drug in the epithelial layer of the respiratory tract - the main zone of replication of the influenza virus - exceeded the average IC 50 for viral neuraminidase about 340 times 12 hours after inhalation and about 52 times 24 hours after inhalation, providing fast inhibition of viral neuraminidase. Zanamivir is deposited mainly in the oral part of the pharynx and lungs (on average, 77.6% and 13.2%, respectively).


Zanamivir is not metabolized and excreted by the kidneys unchanged.


In adult patients with normal renal function, T 1/2 of zanamivir is approximately 2–3 hours.

Pharmacokinetics in special patient groups

Children. The pharmacokinetics of zanamivir was evaluated in an open single-dose study using a nebulizer (10 mg) and a powder inhaler (10 mg) in 24 patients aged 3 months to 12 years. Systemic concentrations in children did not differ from those in adults when using 10 mg of zanamivir in powder form for inhalation.

Elderly patients. With daily use of zanamivir in the form of inhalation in a therapeutic dose of 20 mg, the bioavailability of the drug is low and amounts to 10-20%, therefore, systemic concentrations of zanamivir are insignificant. Correction of the dosage regimen is not required since it is unlikely that any changes in the pharmacokinetic profile associated with age will have clinically significant consequences.

Patients with impaired renal function. With daily use of zanamivir in the form of inhalation in a therapeutic dose of 20 mg, the bioavailability of the drug is low and amounts to 10-20%, therefore, systemic concentrations of zanamivir are insignificant. Given the wide range of safety of zanamivir, a possible increase in systemic concentrations in patients with severe renal failure is not considered clinically significant and does not require correction of the dosage regimen when applied as an inhalation. In patients with severe renal impairment (CC <30 ml/min), T 1/2 from blood serum increases to about 12-20 hours. In patients with end-stage chronic renal failure, zanamivir excretion has not been studied.

Patients with impaired liver function. Since zanamivir is not metabolized, patients with liver failure do not need to adjust the dosage regimen.


  • treatment of infection caused by influenza virus types A and B in children over 5 years old and adults;
  • Prevention of infection caused by influenza virus types A and B in children over 5 years old and adults.

Dosage regimen

The drug Relenza is used only in the form of oral inhalation using the supplied device Diskhaler.

Patients who are prescribed other inhaled medications together with Relenza (for example, fast-acting bronchodilators) should be recommended to use these drugs before using Relenza.


The recommended dose of Relenza is two inhalations (2 × 5 mg) 2 times/day for 5 days. The total daily dose is 20 mg. To achieve the optimal effect, treatment should be started as early as possible (preferably within 2 days) when the first symptoms of the disease appear.

Correction of the dosage regimen in children is not required. Correction of the dosage regimen in elderly patients is not required. In patients with impaired renal and hepatic function, dosage adjustment is not required.


The recommended dose of Relenza is two inhalations (2 × 5 mg) 1 time/day for 10 days. The total daily dose is 10 mg. The period of prophylactic therapy can be increased to one month if the period of the risk of contact with the pathogen of infection exceeds 10 days.

A full course of preventive therapy should be completed as directed. Correction of the dosage regimen in children is not required. In elderly patients, dosage adjustment is not required. In patients with impaired renal and hepatic function, dosage adjustment is not required. Instructions for using the Dealer with Rotadisks. The device Diskhaler is used for inhalation of zanamivir from Rotadisk.

Disaler consists of the following parts:

  • a case with a lid and a plastic needle for piercing a Rotadisk cell;
  • a sliding tray with a mouthpiece and a rotating wheel, on which the Rotadisc is placed.
  • a cover for a mouthpiece.

The rotadisc is placed on the wheel. It should not be used separately until you have read the step-by-step instructions. Rotadisk is a 4-cell blister, each containing 5 mg of zanamivir. The recommended dose of Relenza is two cells (10 mg).

Important! Do not puncture Rotadisk before installing it in the Diskhaler inhalation device. The rotadisk can be stored in the Diskhaler, however, the blister should be punctured immediately before inhalation of the drug. Keep the Disaler clean. After use, wipe the mouthpiece with a clean cloth and cover with a blue cover.

Loading Rotadisk into the Disaler:

  1. Remove the blue case from the mouthpiece. Make sure the mouthpiece is clean inside and out.
  2. Carefully pull out the white drawer until the plastic clips exit, holding the corners of the tray. Pull the tray all the way so that the notches on the side of the clamps are visible.
  3. Pull out the white tray completely by squeezing the notches on the side of the clamps with the thumb and forefinger.
  4. Place the new Rotadisc on the wheel with the label up and the cells down. The cells must match the holes in the wheel.
  5. Insert the tray back into the chassis. If inhalation is not carried out immediately after the installation of Rotadisk, a blue cover should be put on the mouthpiece again. The Rotadisk should be punctured only immediately before inhalation.
  6. While holding the Diskhaler horizontally, raise its lid up to the stop to puncture the upper and lower foil of the Rotadisc. The cover must be in a fully upright position. Close the cover. Disaler is ready to use. The caller with the punctured Rotadisc should be kept horizontal until inhalation.
  7. Take a comfortable sitting position. Without bringing Diskhaler to your mouth, exhale completely. Do not exhale into the inhaler. Otherwise, the powder can be blown out of the blister. After complete exhalation, place the mouthpiece between the teeth and tightly squeeze the lips. Do not grip the mouthpiece with your teeth or close the air holes on both sides of the mouthpiece. Take one quick, deep breath through your mouth. Important! Inhale through the mouth, not through the nose. Remove the mouthpiece from the mouth. Hold your breath as far as possible, then exhale slowly. Preparation of the next cell (the second part of the dose).
  8. Pull out the drawer tray as far as it will go (do not press on the clips or pull out the tray completely) and insert it back. In this case, the Rotadisk will turn one cell and will be ready for the next inhalation. Repeat as necessary until the cell stands under the needle. For inhalation, repeat steps 6 and 7.
  9. After inhalation is completed (usually using two cells), wipe the mouthpiece and close it with a blue cover. It is important to keep the caller clean.
  10. Each Rotadisk contains 4 cells. After four inhalations, remove the empty Rotadisc from the Diskhaler and replace it with a new one (steps 1-5).

Side effect

The drug Relenza is well tolerated when used in the form of oral inhalation. In clinical trials, which included groups of high-risk patients (elderly patients, as well as patients with some chronic diseases), the incidence of adverse reactions is similar in the zanamivir group and the placebo group.

The adverse reactions presented below are listed in accordance with the damage to organs and organ systems and the frequency of occurrence. The frequency of occurrence is determined as follows: very often (≥1 / 10), often (≥1 / 100, <1/10), infrequently (≥1 / 1000, <1/100), rarely (≥1 / 10,000, < 1/1000), very rarely (<1/10 000, including isolated cases).

Frequency categories were formed on the basis of clinical studies of the drug and post-registration observation. On the part of the immune system: very rarely - allergic reactions, including anaphylactic and anaphylactoid reactions, swelling of the face and oropharynx.

From the nervous system: very rarely - vasovagal reactions (were recorded in patients with symptoms of the influenza virus, such as fever, dehydration, observed immediately after the drug Relenza).

From the psyche: the frequency is unknown - convulsions, confusion, behavioral disorders, hallucinations, agitation, anxiety, delirium were recorded with the use of Relenza in patients with influenza, mainly among children and adolescents. Convulsions and neuropsychiatric symptoms were also observed in patients with influenza who were not taking Relenza.

From the cardiovascular system: arrhythmia, fainting. From the respiratory system: very rarely - bronchospasm, shortness of breath.

On the part of the skin and subcutaneous tissue: very rarely - rash, urticaria, severe skin reactions, including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis.

Pregnancy and lactation

The safety of zanamivir during pregnancy has not been established. Studies of reproductive function in rats and rabbits have shown that zanamivir crosses the placental barrier. In studies in rats, there were no signs of teratogenic effects, effects on fertility or clinically significant impairment of peri- or postnatal development of offspring after the use of zanamivir. However, data on the penetration of zanamivir through the placental barrier in humans are not available.

Zanamivir should not be taken by women during pregnancy, especially in the first trimester, unless the expected benefit to the mother outweighs the potential risk to the fetus.

In rats, zanamivir has been shown to pass into breast milk. However, there is no information on the penetration of zanamivir into breast milk in humans.

Due to limited experience, during breastfeeding, zanamivir should be used only when the expected benefit to the mother outweighs the potential risk to the baby.

Special instructions

Influenza virus infection may be associated with increased airway hyperresponsiveness. Very rare reports have been received of bronchospasm and/or impaired respiratory function after zanamivir inhalation in patients during treatment of influenza; some of these patients had no history of respiratory disease. In such cases, it is necessary to stop treatment with zanamivir and consult a specialist for a medical examination. Patients with concomitant respiratory diseases taking inhaled zanamivir should have a fast-acting bronchodilator with them.

In patients with severe bronchial asthma, it is necessary to assess the expected benefits and possible risks when using the drug. Relenza should not be prescribed if proper medical supervision is not carried out. In patients with bronchial asthma and severe severity of chronic obstructive pulmonary disease (COPD), treatment of the underlying disease should be optimized during therapy with Relenza. The patient should be informed of the potential risk of bronchospasm.

Relenza drug, metered-dose powder for inhalation, should not be used to prepare the solution and should be used through a nebulizer or mechanical ventilation device (IVL). There are reports of hospitalization of patients with influenza who were prescribed a solution prepared from zanamivir powder for inhalation and administered through a nebulizer or mechanical ventilator. In addition, a fatal case has been described in which it was reported that lactose, which is part of the drug, provoked obstruction of the equipment. In this regard, the Relenza drug should only be used using the supplied Diskhaler device.

Influenza can be accompanied by various neurological and behavioral symptoms. Messages received in the post-registration period (mainly observed in children in Japan) have reported convulsive seizures, delirium, hallucinations and deviant behavior in influenza patients taking neuraminidase inhibitors, including zanamivir. These phenomena were observed mainly in the early stages of the disease, often characterized by a sudden onset and rapid resolution. A causal relationship between taking zanamivir and the above adverse effects has not been established. If any neuropsychiatric symptoms occur, it is necessary to assess the ratio of risk and benefit of further treatment with zanamivir for each individual patient.