O que é Relenza?
Relenza (zanamivir) is an inhaled antiviral medicamento approved by the Agência Europeia de Medicamentos (EMA) for the tratamento and prevention of influenza A and B. It belongs to the neuraminidase inhibitor class of antiviral drugs — the same class as Tamiflu (oseltamivir), though it is delivered by inhalation rather than orally.
Relenza is delivered directly to the respiratory tract — the primary site of influenza infection — via a breath-activated inhaler device called the Diskhaler. This targeted delivery means that systemic absorption is low (approximately 10–20% of the inhaled dose reaches the bloodstream), which reduces the likelihood of systemic efeito secundários but also means Relenza is not suitable for pacientes who cannot inhale effectively.
Como funciona Relenza work?
Gripe viruses are coated with two surface proteins: haemagglutinin (H) and neuraminidase (N). Haemagglutinin allows the virus to attach to and enter host cells. Neuraminidase allows newly formed virus particles to detach from infected cells and spread to infect additional cells throughout the respiratory tract.
Zanamivir is a neuraminidase inhibitor: it binds directly and selectively to the neuraminidase enzyme on the surface of influenza A and B viruses, blocking its activity. By blocking neuraminidase, zanamivir:
- Prevents newly formed viral particles from detaching from infected cells
- Limits the spread of the virus to additional respiratory cells
- Reduces the total viral load in the respiratory tract
This mechanism is most effective when started early — ideally within the first 24 hours, and no later than 48 hours after symptoms begin — because viral replication is most active in this early phase.
Para quem é Relenza for?
Relenza is indicated for:
Treatment:
- Adults and children aged 5 years and over with symptomatic influenza A or B, when symptoms began within the past 48 hours
- Patients in groups at higher risk of complications (elderly, immunocompromised, those with chronic medical conditions), where antiviral tratamento is particularly warranted
Prevention (post-exposure prophylaxis):
- Adults and adolescents (aged 12 and over) who have been exposed to influenza and require preventive tratamento in certain circumstances, such as during outbreaks
Relenza is generally NOT recommended for:
- Patients with asthma or COPD (significant risk of bronchospasm)
- Patients who cannot use inhaler devices correctly
- Patients under 5 years of age
- People who have not started tratamento within 48 hours of symptom onset (limited benefit)
Dosagem
Relenza is inhaled using the Diskhaler device. Each blister of the Diskhaler contains 5 mg of zanamivir powder.
| Indication | Dose | Frequency | Duration |
|---|---|---|---|
| Treatment (adults and children ≥5 years) | 10 mg (2 inhalations of 5 mg) | Twice daily | 5 days |
| Prevention (post-exposure) | 10 mg (2 inhalations of 5 mg) | Once daily | 10 days |
| Prevention (seasonal / outbreak) | 10 mg (2 inhalations of 5 mg) | Once daily | Up to 28 days |
The two inhalations for each dose should be taken one after the other. Patients with asthma or COPD who are prescribed Relenza despite the risk (in exceptional circumstances) should have a fast-acting bronchodilator available to use before each Relenza dose.
Efeitos secundários
Efeitos secundários comuns
- Bronchospasm: The most clinically important risk — sudden tightening of the airways. Particularly dangerous in pacientes with underlying respiratory disease.
- Headache
- Dizziness
- Throat or nasal irritation
- Nausea
Serious risks
- Severe bronchospasm: Some cases have been fatal, particularly in pacientes with known asthma or COPD. Relenza should be discontinued immediately if bronchospasm occurs and appropriate medical care sought.
- Neuropsychiatric events: Confusion, abnormal behaviour, delirium, and hallucinations have been reported in some pacientes receiving neuraminidase inhibitors, particularly children. Whether these are caused by zanamivir or are a manifestation of influenza itself is unclear.
- Anaphylaxis and allergic reactions: Rare but reported; discontinue immediately if severe hypersensitivity occurs.
Relenza vs Tamiflu
| Feature | Relenza (Zanamivir) | Tamiflu (Oseltamivir) |
|---|---|---|
| Active ingredient | Zanamivir | Oseltamivir |
| Route | Inhaled (Diskhaler) | Oral (cápsula or suspension) |
| Systemic absorption | Low (~10–20%) | High (~80%) |
| Suitable for asthma/COPD | Not recommended | Preferred in respiratory disease |
| Starting age (tratamento) | 5 years and over | 1 year and over |
| Side effect profile | Bronchospasm risk | Mainly GI (nausea, vomiting) |
Tamiflu is generally preferred in pacientes with underlying respiratory disease or those who cannot use inhaler devices. Relenza may be preferred in pacientes who tolerate it and for whom systemic exposure should be minimised.
Como aceder a influenza tratamento online na Europa
Relenza is a medicamento sujeito a receita médica in most estados-membros da UE. Prescrivia operates as a technology intermediary, connecting pacientes with independent EU-registered médicos for online health assessments. We do not prescribe medicamentos, employ médicos, or sell medicamentos directly.
Note on timing: Given that antiviral tratamento for influenza must be started within 48 hours of symptom onset to be effective, prompt medical consultation is critical. If you are experiencing flu symptoms, seek medical assessment as soon as possible.
Important: A Prescrivia não garante that a receita médica will be issued. All clinical decisions are made independently by qualified medical professionals.
Informação de segurança importante
Não utilize Relenza if you:
- Have asthma or chronic obstructive pulmonary disease (COPD)
- Cannot use inhaler devices effectively
- Are allergic to zanamivir or any excipient in Relenza
Stop Relenza and procure assistência médica imediata if you:
- Experience difficulty breathing, wheezing, or chest tightness after inhalation (bronchospasm)
- Develop severe allergic symptoms
Vaccinate: Annual influenza vaccination remains the most important preventive measure against influenza and its complications, per WHO recommendations.
Fontes
Medical information on this page is based on the following sources:
- Agência Europeia de Medicamentos (EMA). Relenza (zanamivir) — Summary of Product Characteristics. ema.europa.eu
- Organização Mundial da Saúde (WHO). Gripe (Seasonal) — Fact sheet. who.int
- Organização Mundial da Saúde (WHO). WHO guidelines for pharmacological management of pandemic and seasonal influenza. 2010. who.int
This content is reviewed periodically to reflect updated clinical guidance. It is provided for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for advice relevant to your individual health circumstances.
Frequently asked questions
- O que é Relenza utilizado para?
- Relenza (zanamivir) is an inhaled antiviral medicamento used to treat influenza A and B in adults and children aged 5 years and over when they are showing flu symptoms. It is also used to prevent influenza in adults and adolescents in certain circumstances. Relenza must be started within 48 hours of the first appearance of flu symptoms to be effective.
- Why must Relenza be started within 48 hours?
- Gripe viruses replicate most rapidly in the first 24–48 hours of infection. Zanamivir works by blocking neuraminidase — an enzyme the virus uses to release copies of itself from infected cells and spread to new cells. Starting tratamento early, when viral replication is still active, significantly limits the extent of infection and shortens the duration of illness. Starting after 48 hours has passed provides little clinical benefit.
- Como é Relenza taken?
- Relenza is inhaled using a breath-activated inhaler device called a Diskhaler. Each dose consists of two inhalations (2 x 5 mg = 10 mg per dose), taken twice daily for 5 days. The Diskhaler contains a blister pack of powdered zanamivir and requires the paciente to breathe in through the device to deliver the medication to the airways.
- Can people with asthma or COPD use Relenza?
- Caution is required. Relenza is inhaled as a powder, and has been associated with bronchospasm (sudden narrowing of the airways) in pacientes with underlying respiratory conditions such as asthma or COPD. Some pacientes have experienced severe and even fatal bronchospasm shortly after inhaling zanamivir. Relenza should generally not be used in pacientes with asthma or COPD; Tamiflu (oseltamivir) oral cápsulas are typically preferred in this group.
- Is Relenza the same as Tamiflu?
- Both Relenza (zanamivir) and Tamiflu (oseltamivir) are neuraminidase inhibitor antivirals used to treat influenza, and they have a similar mechanism of action. The key differences are the route of administration (Relenza is inhaled; Tamiflu is taken orally), their efeito secundário profiles, and their suitability for pacientes with respiratory conditions. A médico can advise which is most appropriate for individual pacientes.
Tratamentos
A Prescrivia é apenas uma plataforma intermediária. Não prestamos serviços médicos, não prescrevemos tratamentos nem dispensamos medicamentos. Todas as decisões médicas são tomadas por médicos independentes registados na UE. Todos os medicamentos são dispensados por farmácias licenciadas na UE. Esta plataforma facilita a ligação entre pacientes e prestadores de cuidados de saúde.