O que é Tamiflu?
Tamiflu (oseltamivir phosphate) is an oral antiviral medicamento approved by the Agência Europeia de Medicamentos (EMA) for the tratamento and prevention of influenza A and B. It is the most widely used antiviral medicamento for influenza globally, recommended by the Organização Mundial da Saúde (WHO) for use in at-risk populations and during influenza pandemics.
Tamiflu belongs to the neuraminidase inhibitor class of antivirals — the same class as Relenza (zanamivir) — and works by interfering with a protein on the surface of influenza viruses that is essential for viral spread. Unlike Relenza, which is delivered directly to the lungs by inhalation, Tamiflu is taken orally and is absorbed systemically.
Como funciona Tamiflu work?
Gripe viruses reproduce by infecting respiratory cells, replicating inside them, and then using a surface enzyme called neuraminidase to release new viral copies into the airway, allowing them to infect further cells. This cycle of infection and spread is what causes the progressive worsening of flu symptoms in the first days of illness.
Oseltamivir (the active ingredient in Tamiflu) is a prodrug — it is converted in the body to oseltamivir carboxylate, which is the pharmacologically active form. Oseltamivir carboxylate is a potent inhibitor of neuraminidase on both influenza A and influenza B viruses. By blocking neuraminidase:
- New viral particles are trapped on the surface of infected cells and cannot spread to new cells
- The total viral load in the respiratory tract is reduced
- The duration and severity of infection is shortened
Tamiflu has high oral bioavailability (approximately 80% of the oral dose is absorbed), meaning it reaches adequate concentrations throughout the body, including in the respiratory tract.
Para quem é Tamiflu for?
Treatment: Tamiflu is indicated for the tratamento of influenza A and B in:
- Adults and adolescents
- Children aged 1 year and over
It is particularly important for pacientes at increased risk of serious complications from influenza, including:
- Older adults (aged 65 and over)
- Immunocompromised individuals
- Patients with chronic respiratory conditions (including asthma, COPD)
- Patients with chronic cardiovascular, renal, hepatic, or metabolic diseases
- Pregnant and postpartum women
Prevention (prophylaxis): Tamiflu is approved for prevention of influenza following close contact with an infected person (post-exposure prophylaxis) in adults and children aged 1 year and over.
Tamiflu is most effective when:
- Started within 48 hours of symptom onset (tratamento)
- Started within 48 hours of exposure (post-exposure prevention)
Dosagem
Treatment
| Group | Dose | Frequency | Duration |
|---|---|---|---|
| Adults and adolescents (≥13 years) | 75 mg | Twice daily | 5 days |
| Children (1–12 years) | Weight-based dosing | Twice daily | 5 days |
| Patients with renal impairment | Dose reduced by médico | — | 5 days |
Prevention
| Group | Dose | Frequency | Duration |
|---|---|---|---|
| Adults and adolescents (≥13 years) | 75 mg | Once daily | 10 days (post-exposure) |
| Seasonal prevention | 75 mg | Once daily | Up to 6 weeks |
Tamiflu cápsulas (30 mg, 45 mg, 75 mg) and an oral suspension (12 mg/mL) are available. The oral suspension is particularly suitable for children and adults who cannot swallow cápsulas. Taking Tamiflu with food reduces the likelihood of nausea.
Efeitos secundários
Very common and common efeito secundários
- Nausea: The most frequently reported efeito secundário; significantly reduced if Tamiflu is taken with food. Nausea typically improves after the first one to two days.
- Vomiting: More common in children than adults
- Headache
- Abdominal pain
- Diarrhoea
Serious risks
- Neuropsychiatric events: Reports of confusion, delirium, abnormal behaviour, and hallucinations — predominantly in children and adolescents. It is unclear whether these are caused by the medicamento, by influenza infection itself, or by a combination. Patients and caregivers should be alert to any unusual behaviour.
- Skin reactions: Rare cases of serious skin reactions (erythema multiforme, Stevens-Johnson syndrome) have been reported. Stop Tamiflu and seek medical attention for any significant skin changes.
- Anaphylaxis: Very rare; discontinue and seek emergency care if severe allergic symptoms develop.
Note: Many of the neuropsychiatric events reported with Tamiflu have occurred in countries with higher rates of influenza-associated encephalopathy, and the causal relationship with the medicamento is debated. The EMA continues to monitor this safety signal.
Tamiflu vs Relenza
| Feature | Tamiflu (Oseltamivir) | Relenza (Zanamivir) |
|---|---|---|
| Route | Oral | Inhaled (Diskhaler) |
| Systemic absorption | High (~80%) | Low (~10–20%) |
| Suitable for asthma/COPD | Yes (preferred) | Not recommended |
| Main efeito secundários | Nausea, vomiting | Bronchospasm risk |
| Minimum age (tratamento) | 1 year | 5 years |
| Availability | Capsules and oral suspension | Inhalation powder |
Tamiflu is generally the preferred influenza antiviral for most pacientes, including those with respiratory conditions. Relenza may be considered in specific circumstances, such as where oral administration is not possible.
Como aceder a Tamiflu online na Europa
Tamiflu 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.
Critical timing note: Since antiviral tratamento for influenza must be started within 48 hours of symptom onset to be maximally effective, it is essential to seek a medical assessment promptly if you develop flu symptoms. Do not delay in contacting a médico.
If an independent médico determines that oseltamivir is clinically appropriate, they may issue a receita médica, which is then fulfilled by a licensed EU farmácia partner.
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
Informe o seu médico if you:
- Have kidney disease (dose adjustment may be required)
- Are pregnant or breastfeeding
- Are giving Tamiflu to a child (use weight-based dosing as directed)
Watch for and report:
- Unusual behaviour, confusion, or hallucinations (particularly in children)
- Severe skin reactions
- Worsening of breathing difficulties
Vaccination: Annual influenza vaccination remains the most effective preventive strategy against influenza and its complications. Tamiflu is a tratamento tool, not a substitute for vaccination. The WHO recommends annual flu vaccination for all at-risk groups.
Antiviral resistance: While oseltamivir resistance in circulating influenza strains has been recorded (particularly in certain H1N1 strains), surveillance data from the WHO and ECDC indicates that most circulating influenza viruses remain susceptible to oseltamivir.
Fontes
Medical information on this page is based on the following sources:
- Agência Europeia de Medicamentos (EMA). Tamiflu (oseltamivir) — 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
- Jefferson T, et al. Oseltamivir for influenza in adults and children: systematic review of clinical study reports and summary of regulatory comments. BMJ. 2014;348:g2545.
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 Tamiflu utilizado para?
- Tamiflu (oseltamivir) is an oral antiviral medicamento used to treat influenza A and B in adults and children aged 1 year and over. It is also approved to prevent influenza following exposure, or during outbreaks. Like all influenza antivirals, Tamiflu must be started as soon as possible after symptom onset — ideally within 48 hours — to be effective.
- How much does Tamiflu shorten the duration of flu?
- Clinical trial data reviewed by the EMA indicates that Tamiflu can reduce the duration of influenza symptoms by approximately 1–2 days compared to placebo when started within 48 hours of symptom onset. Evidence also suggests a reduction in the risk of serious complications such as pneumonia and hospitalisation, particularly in at-risk populations.
- Can I take Tamiflu to prevent flu after being exposed?
- Yes. Tamiflu is approved for post-exposure prophylaxis (prevention) in adults and children aged 1 year and over who have been exposed to influenza. The preventive dose is lower than the tratamento dose and is taken once daily for 10 days following exposure. Tamiflu is not a substitute for flu vaccination, which remains the primary preventive measure.
- What are the main efeito secundários of Tamiflu?
- The most commonly reported efeito secundários of Tamiflu are nausea and vomiting, which occur in a minority of pacientes and are typically mild to moderate. Taking Tamiflu with food significantly reduces the risk of nausea. Headache, abdominal pain, and diarrhoea are also reported. Rarely, neuropsychiatric events including confusion and abnormal behaviour have been reported, particularly in children.
- Is Tamiflu suitable for people with asthma or COPD?
- Yes, Tamiflu is generally considered suitable for pacientes with asthma or chronic obstructive pulmonary disease (COPD). Unlike Relenza (zanamivir), which is inhaled and carries a risk of bronchospasm, Tamiflu is taken orally and is therefore preferred in pacientes with underlying respiratory conditions. Patients with severe respiratory disease should consult their médico.
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.