NEW YORK (Reuters Health) Extended-duration treatment with the neuraminidase inhibitors (NAIs) oseltamivir or zanamivir can help prevent symptomatic influenza in immunocompetent adults, a review and analysis of trial data suggest.

ìIn the context of the emergence of and ongoing pandemic caused by a novel influenza A (H1N1) virus of swine origin that is resistant to adamantanes, but susceptible to NAIs, and the projected 4 to 6 month delay to availability of a matched vaccine, chemoprophylaxis with NAIs could be used for prevention strategies, lead author Dr. Nayer Khazeni, from Stanford University Medical Center, California, and colleagues point out.

To assess the safety and efficacy of extended-duration (> 4 weeks) prophylaxis with these agents, the researchers analyzed data from seven randomized, placebo-controlled trials identified through a search of MEDLINE, EMBASE, and other sources. Together, the studies featured 7021 subjects, according to the report in the August 3rd online issue of the Annals of Internal Medicine.

Relative to placebo use, treatment with an NAI reduced the likelihood of symptomatic influenza by 74%, Dr. Khazeni and colleagues report. Oseltamivir and zanamivir were comparable in this regard.

By contrast, NAI use did not prevent asymptomatic infection with influenza virus, the results indicate.

In general, NAI therapy did not increase the risk of adverse events. However, an increased rate of nausea and vomiting was noted in subjects treated with oseltamivir.

Regarding the limitations of their analysis, the researchers comment that none of the trials they reviewed were “powered to detect rare adverse events, and none included diverse racial groups, children, immunocompromised patients, or individuals who received live-attenuated influenza virus vaccine.”

Thus, they conclude, there is a need for studies that address these issues.

Reference:
Ann Intern Med 2009.