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Tamiflu (oseltamivir)


Conclusion

Tamiflu is a new product in capsule form which can be used both for the prevention and treatment of influenza. If treatment is initiated within two days after the onset of symptoms, the duration of illness is shortened by about one day (normal duration is five to seven days).

 

Tamiflu can also be used to prevent influenza in people who have most likely been exposed to the illness: it reduces an individual’s risk of contracting influenza from 12% to 1%. In either case, the price per pack for the treatment of one person is DKK 249.95.  To avoid one person contracting influenza, ten people must be treated for seven days.

 

Patients with a high risk of developing complications as a result of influenza should still be vaccinated (see Danish National Board of Health guidelines). Tamiflu can be used prophylactically for high-risk patients who have not been vaccinated for some reason or another. To prevent one case during an influenza outbreak, roughly 25 people must be treated for six weeks, at a total cost of about DKK 26,000.

 

Background

Tamiflu (oseltamivir) is a new antiviral medicinal product in capsule form for the treatment and prevention of influenza, and it has been marketed in Denmark since 30 September 2002. Tamiflu is currently the only medicinal product registered for the treatment of influenza, but the prophylactic treatment used today is vaccination. Tamiflu may be used for the treatment of adults and children aged one or older. However, the currently available capsule formulation can only be used for people who weigh more than 40 kg; paediatric treatment guidelines will be posted as soon as an oral suspension is on the market. Prophylactic (longer-term) treatment has not been studied in children under 13, so it should not be used for this group.

 

  • Treatment of influenza should be initiated as early as possible in the course of the illness. The adult dose is one capsule (75 mg) twice daily for five days.
  • For post-exposure prophylaxis, administration of 75 mg once daily only for at least one week is recommended.
  • For prophylactic treatment during an influenza outbreak in the community, people should be treated for up to six weeks. Tamiflu is not a replacement for influenza vaccination in high-risk groups, and the duration of protection lasts only as long as it is administered.

Efficacy

The efficacy of Tamiflu has not been compared with that of other therapies (Relenza or vaccination). Two studies with a total of 1355 otherwise healthy patients aged 18-65 with classic influenza symptoms compared the efficacy of five days’ treatment with Tamiflu 75 mg twice daily and 150 mg twice daily with that of placebo. The primary efficacy endpoint was the time from onset of treatment to symptom alleviation, which was defined as no or mild symptoms for a period of at least 24 hours. In the case of all the patients treated (of whom about 63% were confirmed influenza-positive), Tamiflu 75 mg twice daily shortened the duration of illness by less than 24 hours (18.5 and 20.7 hours). The duration of illness was shortened by an additional ten hours (29.1 and 31.8 hours) in the influenza-positive patients.

 

An independent analysis of 257 persons in whom treatment with either Tamiflu 75 mg or placebo was initiated within 24 hours demonstrated an additional reduction in duration of illness (a total of 37.8 hours). Doses of 150 mg instead of 75 mg provided no added efficacy.

 

On the other hand, studies of high-risk patients (elderly patients over 65 and patients with chronic heart or lung disease) found no significant reduction in duration of illness when Tamiflu and placebo were compared. It must be mentioned, however, that almost half of the elderly patients had been vaccinated against influenza.

 

Post-exposure prophylaxis

In a study in which 962 family members of influenza patients were treated with Tamiflu 75 mg for seven days within two days of known exposure, the incidence of new influenza cases was also found to be significantly lower (1% versus 12%); the NNT was approximately ten.

Prophylaxis during an influenza epidemic.

Studies of both adult and elderly patients have shown that Tamiflu significantly reduces the number of influenza cases when six weeks of preventive treatment is given during an influenza outbreak. The NNT was 25; many of the elderly patients were vaccinated against influenza.

 

Adverse drug reactions

The most common adverse effects are nausea and vomiting, which were observed in about 8% of the patents on the first or second day of treatment (significant relative to placebo). In patients receiving prophylactic treatment for six weeks, the incidence of pain, colds, dyspepsia and upper respiratory airways infections was higher than in the placebo group.

 

Drug interactions

No interactions of clinical importance.

 

Cost

A pack with 10 capsules cost DKK 249.95 on 30 September 2002.

 

Tamiflu Dosage/duration Product price
Treatment 75 mg twice daily for 5 days DKK 249.95
Post-exposure prophylaxis 75 mg once daily for at least 7 days DKK 175-249.95
Prophylaxis in an influenza outbreak 75 mg once daily for 6 wks. DKK 1050

 

 

General reimbursement is not granted for this product. The product price for an influenza vaccination is about DKK 60.

 

Additional information can be found in the summary of product characteristics.

 


Last modified: September 30th 2002


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