Updated reviews issued for oseltamivir, zanamivir use in flu

(HealthDay)—Oseltamivir and zanamivir reduce the time to symptomatic improvement in influenza by about half a day, but evidence to support claims of reduced admissions to hospital or complications of influenza is lacking, according to two systematic reviews of regulatory information published online April 10 in BMJ.

Tom Jefferson, Ph.D., from the Cochrane Acute Respiratory Infections Group in Rome, and colleagues conducted a systematic review of clinical study reports and regulatory information to describe the potential benefits and harms of oseltamivir. Twenty-three trials were included in a reliability and completeness screen and 20 in a formal analysis. The researchers found that oseltamivir reduced the time to first alleviation of symptoms by 16.8 hours in treatment trials on adults, and had an effect in some children. In prophylaxis trials, oseltamivir reduced symptomatic influenza by 55 percent in participants, but had no significant effect on asymptomatic influenza and no indication of a reduction in transmission. In treatment
trials there was no difference in admissions to hospital in adults (risk difference, 0.15 percent; 95 percent confidence interval, −0.91 to 0.78 percent; P = 0.84)
and sparse data in children and for prophylaxis.

Carl J. Heneghan, M.D., from the University of Oxford in the United Kingdom, and colleagues conducted a systematic review of clinical study reports and regulatory information to describe the potential benefits and harms of zanamivir. Twenty-eight trials were assessed for appropriate study design and 26 were included in a formal analysis. The researchers found that in adults, zanamivir correlated with 0.60-day reduction in the time to first alleviation of symptoms of influenza-like illness. Zanamivir prophylaxis correlated with a reduction in symptomatic influenza in individuals (risk difference, 1.98 percent).

"Zanamivir reduces the time to symptomatic improvement in adults (but not in children) with influenza-like illness by just over half a day, although this effect might be attenuated by symptom relief medication," Heneghan and colleagues write. "We found no evidence that zanamivir reduces the risk of complications of influenza, particularly pneumonia, or the risk
of hospital admission or death."

Several authors from both studies disclosed financial ties to pharmaceutical companies, including GlaxoSmithKline, the manufacturer of zanamivir (Relenza).

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