New neuraminidase inhibitors for influenza: Current and potential therapeutic roles

Although vaccination remains the most effective preventive intervention aga inst influenza, many persons still become infected during annual epidemics. Two new antiviral agents, zanamivir and oseltamivir phosphate, each with s pecific activity against influenza virus neuraminidase, have recently becom e available for the treatment of influenza. These compounds appear to provi de advantages over the older antiviral agents amantadine and rimantadine, i ncluding activity against influenza B virus, fewer side effects, and reduce d risk of viral resistance. Zanamivir, which is poorly absorbed from the ga strointestinal tract, is formulated as a powder for oral inhalation; oselta mivir is formulated as a capsule taken orally. If administered within. 2 da ys of symptom onset, zanamivir and oseltamivir can reduce the duration of u ncomplicated influenza illness by approximately 1 to 1.5 days. The two comp ounds appear to be equally effective, although no direct comparative studie s have been reported. Both agents have shown efficacy in the prevention of influenza, although they are not currently licensed for this use.