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Tamiflu (Oseltamivir) Doesn’t Offer Relief Promised, Study Says

Prescriptions are usually written after 24-hour window of opportunity (Oct. 25)

New research from the University of Georgia College of Public Health indicates that the influenza drug Tamiflu (oseltamivir, Genentech) may not have all of the benefits that flu sufferers and physicians are hoping for.

“Based on published trials and the conventional wisdom, we thought Tamiflu prevents complications, prevents hospitalizations, and is especially good in the vulnerable populations, but we didn’t find support for any of that,” said Dr. Mark Ebell, associate professor of epidemiology.

The findings were based on a meta-analysis of three published and eight unpublished double-blind, placebo-controlled clinical trials of Tamiflu that were conducted in several countries between 1997 and 2000.

The results of the new study will be published in an upcoming issue of Family Practice.

While other reviews have reported reductions in complications due to Tamiflu’s medicinal effect, Ebell’s analysis found no decrease. His team’s analysis eliminated the inclusion of acute bronchitis, a self-limiting viral illness, as a complication and considered only pneumonia, sinusitis, and otitis media as complications requiring antivirals.

“We saw a small difference in the likelihood that pneumonia would develop in those patients who were later confirmed to have influenza, but it was only a 0.9% reduction,” Ebell said. “However, if you look at all patients given oseltamivir for suspected influenza, which is what happens in practice, there was no difference in pneumonia. So, we found no real difference in the likelihood of important complications.”

Ebell and his team also evaluated the duration of symptoms. “When we looked at the data, they were actually pretty disappointing,” Ebell said. “In the published studies, there appeared to be about a 30-hour benefit for people with confirmed influenza, but when we looked at all the data and looked at who would be given the drug in the primary care office with suspected flu, there was only about a 20-hour benefit.”

For patients who waited longer than 24 hours to seek care, the benefits decreased dramatically.

“That makes sense based on what we know about how the drug works,” he said.

Tamiflu prevents respiratory cells from bursting open and releasing viral particles. Once cells begin to burst, the medication loses its effectiveness. Too often, physicians will write prescriptions long after the 24-hour window of treatment closes, Ebell said.

While most of the trials enrolled participants who were generally healthy, two studies selectively included people who were over 65 years of age, and another study looked specifically at patients with cardiopulmonary disease. However, these studies were not published, and none of them found a reduction in complications in these high-risk populations.

Overall, hospitalizations were uncommon, occurring in 33 of 2,633 patients treated with Tamiflu and in 22 of 1,694 patients given placebo.

Source: University of Georgia, October 25, 2012.

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