Study: Tamiflu shortens length of flu symptoms

Antiviral drug oseltamivir (Tamiflu, Roche) shortens the length of flu symptoms by about 1 day, and reduces respiratory infections that sometimes develop by 44%, according to a study published in The Lancet.

The research was conducted by the University of Michigan, the London School of Hygiene and Tropical Medicine, and the University of Alabama.

They conducted a meta-analysis of data from all published and unpublished clinical trials from 1997 to 2001 to determine oseltamivir's effectiveness. More than 4,300 patients were involved in the trials, more than half of whom were treated with the drug, according to a University of Michigan press release.

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The research used data made available by the drug’s manufacturer and analyzed by an independent research group.

Oseltamivir is in a class of drugs known as neuraminidase inhibitors. They block the enzyme activity that occurs in influenza type A and B viruses. Most of the patients studied had influenza type A, with the most prevalent strain reported as H3N2, the same one that is hitting much of the United States this year.

When used at the normal prescribed dosage of 75 mg twice a day for adults, within 36 hours following development of at least 2 flu symptoms, oseltamivir was shown to reduce the duration of the illness by 21%. With the drug, symptom alleviation occurred, on average, at 98 hours compared with 123 hours with placebo.

The researchers found no benefit in adults who did not have the flu virus, confirming the drug's role as an antiviral.

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In addition to reducing the risk of respiratory tract infections requiring antibiotics, such as pneumonia (4.9% had complications with the drug compared with 8.7% on placebo), oseltamivir decreased hospital admissions by 63% (0.6% vs. 1.7%).

The researchers also found some of the same complications of the drug noted in previous research, with an increase in nausea (3.7%) and vomiting (4.7%). They did not find differences between the 2 groups with respect to development of neurological or psychological disorders that had been raised in previous research.

 "[This] data . . . is reassuring in that the statistical methodology is accepted and the studies deemed valid,” said Victoria Richards, associate professor of medical sciences at the Frank H. Netter MD School of Medicine at Quinnipiac University, Hamden, Conn. “This type of analysis supports the claims that the use of oseltamivir in adults reduces the duration of symptoms of laboratory-confirmed influenza virus infection."

But it also indicates a reduced risk of certain complications of diagnosed influenza, such as bronchitis, pneumonia, and lower respiratory tract infections; all of which can be dangerous in certain adults with influenza, according to Richards.

“Other comforting data revolves around how oseltamivir reduced hospital admission rates for any reason in those with influenza virus infection; again positive given the current status on our healthcare system,” she said. “Overall, this is positive news and should help prescribers with appropriate use of the drug; however, the nausea and vomiting associated with oseltamivir use may outweigh the benefits in some patients."

As with evidence-based pharmacotherapy, prescribers should weigh the benefits and risks of oseltamivir use and clearly communicate with their patients on all treatment options, Richards said.