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April 23, 2014
How Effective Are Neuraminidase Inhibitors in Influenza?
Oxford, UK—While oseltamivir shortens symptoms of influenza by half a day, no good evidence supports claims that the drug, marketed as Tamiflu, reduces admissions to hospitals or complications of influenza, according to an updated Cochrane evidence review. In light of the review, published jointly by the Cochrane Collaboration, the independent, global healthcare research network, and the British Medical Journal (BMJ), worldwide stockpiling of the neuraminidase inhibitors in preparation for an influenza epidemic is being called into question. The review also notes that while Tamiflu can reduce the risk of flu symptoms, it remains unproven that the drug can prevent the spread of the illness. Neuraminidase inhibitors also cause a variety of side effects, including nausea and vomiting, headaches, psychiatric disturbances, and renal events, according to the report. For the review, investigators looked at full internal reports of 20 trials of oseltamivir and 26 trials of zanamivir, marketed as Relenza, involving more than 24,000 patients. Authors note that assumptions about the effectiveness of Tamiflu against complications were used when governments around the world decided to stockpile the drugs in case of a pandemic. For example, the United States has spent more than $1.3 billion buying a strategic reserve of antivirals, according to the article. Cochrane analysts note that attempts were made to verify the safety and effectiveness of Tamiflu in 2009, but researchers were unable to get access to trial data. Compared with a placebo, taking Tamiflu led to a quicker alleviation of influenza-like symptoms of half a day—from seven to 6.3 days—in adults, while the effect in children was more uncertain, according to the analysis. No evidence was found of a reduction in hospitalizations or serious influenza complications, such as confirmed pneumonia, bronchitis, sinusitis, or ear infection in either adults or children, the authors point out. In addition, Tamiflu also increased the risk of nausea and vomiting in adults by around 4% and in children by 5%, according to the review, which also found some evidence that Tamiflu prevented some patients from producing sufficient numbers of their own antibodies to fight infection. “In prophylactic studies, oseltamivir reduces the proportion of symptomatic influenza. In treatment studies it also modestly reduces the time to first alleviation of symptoms, but it causes nausea and vomiting and increases the risk of headaches and renal and psychiatric syndromes,” according to the authors. “The evidence of clinically significant effects on complications and viral transmission is limited because of rarity of such events and problems with study design. The trade-off between benefits and harms should be borne in mind when making decisions to use oseltamivir for treatment, prophylaxis, or stockpiling.” In commenting on the study, Dr. Fiona Godlee, BMJ’s editor-in-chief, noted the difficulty in getting effectiveness information for the drug class. “This review is the result of many years of struggles to access and use trial data, which was previously unpublished and even hidden from view. It highlights with certainty that future decisions to purchase and use drugs, particularly when on a mass scale, must be based on a complete picture of the evidence, both published and unpublished,” Godlee said “We need the full data from clinical trials made available for all drugs in current use. With the new European Clinical Trials Directive bringing in rules for future drugs, it highlights the enormous challenge we face. We need the commitment of organizations and drug companies to make all data available, even if it means going back 20 years. Otherwise we risk another knee-jerk reaction to a potential pandemic. And can we really afford it?”
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U.S. Pharmacist Social Connect
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