Researchers say the popular antiviral flu drugs Tamiflu and Relenza are not as effective as doctors and public health experts were led to believe, in the most comprehensive review of data on the effectiveness of the two drugs.
There isn't strong evidence to support stockpiling the products in national emergency drug depots in case of a pandemic, the researchers say. Both drugs—Tamiflu is the brand name for oseltamivir and Relenza is the brand name zanamivir—are designed to stop the influenza virus from spreading in an infected person, and claim to reduce the severity of flu symptoms and how long people are sick. The Centers for Disease Control and Prevention keeps the drugs in its stockpile for use in both seasonal and pandemic flu situations, and the European Medicines Agency (EMA) and the World Health Organization also recommend the medications for treating flu.
The authors of the current review found, however, that in the case of the European approvals in particular, regulatory agencies relied on summaries of studies rather than an exhaustive analysis of raw data, known as clinical study reports, which can run to more than 1,000 pages and detail methods, protocols and statistical analyses.
After a four-year effort to obtain this data from both the manufacturers and the EMA, the authors report in the journal BMJ that those trials do not support claims that the drugs lower the risk of complications from flu, such as pneumonia, or that the benefits of the drugs outweigh their risks, which include nausea, vomiting, headaches and kidney disorders.
The authors point to not just one failure in the process of approving these medications, but a weak regulatory system in which the studies are all conducted by manufacturers, and in which the trials compared the medications against placebo rather than to existing flu treatments.
Given that the more comprehensive review found little support for recommending oseltamivir to reduce flu symptoms or hospitalization due to complications from flu, the authors write: “We believe these findings provide reason to question the stockpiling of oseltamivir, its inclusion on the WHO list of essential drugs, and its use in clinical practice as an anti-influenza drug.” On zanamivir, they said “Our findings do not support the mode of action of zanamivir proposed by the manufacturer.”