Drug Profile

Oseltamivir (TAMIFLU) was approved by the Food Drug Administration (FDA) in October 1999, following zanamivir (RELENZA) as the second drug cleared to treat uncomplicated flu infections in people who have had symptoms of the flu for no longer than two days.

In November 2000, oseltamivir received further FDA approval to prevent flu. Several studies have confirmed the effectiveness of oseltamivir for prevention. The drug must be started within two days of close contact with a flu-infected individual. Oseltamivir is approved to be taken for up to 42 days to prevent the flu, but protection only lasts as long as the drug is being taken. The safety and effectiveness of repeated courses for prevention of flu has not been studied.[1] A 2006 Cochrane review concluded that for prevention of influenza, "compared to placebo, NIs [neuraminidase inhibitors, which include drugs such as Relenza or Tamiflu] have no [significant] effect against influenza-like illness."

The same Cochrane Collaboration review concluded that “Because of their low effectiveness, NIs should not be used in routine seasonal influenza control. In a serious epidemic or pandemic, NIs should be used with other public health measures.”[2]

Oseltamivir reduces the duration of the flu by about 1.3 days, which the director of the FDA’s Division of Antiviral Drug Products described as "modest." The director also noted that “the clinical relevance of the modest treatment benefit is a highly subjective question.”[3]

In our opinion, because of its limited effect on the duration of the flu, the cost of oseltamivir outweighs the “benefit” in the treatment of an illness that runs a definite, limited course in the vast majority of people.

Studies say…

Oseltamivir has failed to achieve impressive results in multiple clinical trials. In clinical studies, there was no difference in the incidence of complications of the flu between patients taking oseltamivir and those taking a placebo.

The effectiveness and safety of oseltamivir in the treatment of patients with chronic heart or respiratory disease is unknown.[1]

The editors of Prescrire International, a highly regarded French source of independent drug information for health professionals, found:

Oseltamivir is only moderately effective at preventing influenza, and there is no evidence that it differs from amantadine in this respect. In patients with suspected influenza during an epidemic, the effects of oseltamivir are also moderate, and similar to those of zanamivir and amantadine. No impact on the frequency of complications has been shown in adults or children at risk.[4]

However, safety concerns about oseltamivir use in both children and adults have been raised. As of Feb. 4, 2006, 39 deaths had been associated with oseltamivir in Japan, 13 of which were children aged 16 and under.[5] Several of the deaths in children involved falls from high places.[6]

Oseltamivir is not indicated for use in pediatric patients younger than 1 year of age.[7]

Discussing the use of oseltamivir in the prevention of influenza in children, the editors of Prescrire wrote:

The clinical evaluation of oseltamivir in the prevention of influenza in children is woefully inadequate. There is no firm evidence that oseltamivir reduced the incidence of complications associated with influenza. Adverse effects can be severe, and the potential for the development of viral strains resistant to oseltamivir is of concern. It is better simply to vaccinate at-risk children.[8]

In June 2023, JAMA Internal Medicine published an article showing limited evidence that oseltamivir reduces hospitalizations or prevents complications associated with the flu in patients who are not in a hospital, nursing home or other institution (outpatient).[9]

Regulatory actions surrounding oseltamivir

2006: In November, manufacturer Roche revised the FDA-approved drug label of oseltamivir to include reports of abnormal behavior that, in extreme cases, resulted in death. These reports, mostly from Japan, primarily involved children and adolescents.[7]

2008: The FDA and manufacturer Roche issued an advisory warning regarding neuropsychiatric events associated with the use of oseltamivir. Most of these reports were from Japan and included delirium and abnormal behavior leading to injury and, in some cases, death.[10]

The current labeling for oseltamivir states that: “Patients with influenza should be closely monitored for signs of abnormal behavior. If neuropsychiatric symptoms occur, the risks and benefits of continuing treatment should be evaluated for each patient.”

2009: The FDA issued a Public Health safety alert in September 2009 alerting health care professionals and the public to the potential of dosing errors with oseltamivir for oral suspension. Health care providers in the United States usually write prescriptions for liquid medication in milliliters (mL) or teaspoons. The dosing dispenser for oseltamivir is dosed in milligrams (mg). Reports of dosing errors have occurred when the dosing instructions do not match the dosing dispenser.[11]

2012: In December, the FDA issued the following statement: “Safety and efficacy of TAMIFLU for treatment of influenza in pediatric patients less than 2 weeks of age have not been established. Safety and efficacy of TAMIFLU for prophylaxis of influenza have not been established for pediatric patients less than 1 year of age.”[12]