Influenza treatment with oseltamivir outside of labeled recommendations

Published evidence regarding the use of the antiinfluenza agent oseltamivir outside of the standard dosing recommendations is reviewed.Oseltamivir is a neuraminidase inhibitor indicated for the treatment of uncomplicated influenza in patients two weeks of age or older who have been symptomatic for no more than two days; the recommended dosage is 75 mg twice daily by mouth for five days. A literature search identified six studies evaluating the effects of administering oseltamivir 48 hours or more after the onset of influenza symptoms, administering the drug at double the standard dose, or continuing therapy for more than five days. Two randomized controlled trials found that double-dose oseltamivir therapy conferred no significant survival benefit. The results of one retrospective study of intensive care unit (ICU) patients infected with the influenza H1N1 strain suggested improved survival among those who received oseltamivir no later than five days after symptom onset.Oseltamivir may increase survival when used within five days of symptom onset in influenza H1N1-infected patients who require ICU admission. There appears to be no benefit in starting treatment more than 48 hours after symptom onset in hospitalized general medicine patients or outpatients infected with either H1N1 or other influenza strains or in doubling the dose of oseltamivir in hospitalized patients or outpatients. There are scant data supporting the use of oseltamivir for longer than five days in any patient population, with the possible exception of critically ill H1N1-infected ICU patients, who may benefit from extended treatment in some cases.