Neuraminidase inhibitors: progress in the management of influenza.

Influenza is a serious respiratory illness and represents a significant clinical burden. As well as being debilitating, influenza can often cause complications leading to hospitalisation and death. Prophylaxis by vaccination is the preferred method of disease management, but because influenza viruses are constantly changing their antigenic properties, influenza outbreaks occur regularly as epidemics. Neuraminidase inhibitors are a new class of anti-influenza drugs designed to block influenza virus replication. Two neuraminidase inhibitors, zanamivir and oseltamivir, have been licensed for clinical use in the treatment of influenza. Both drugs significantly reduce the severity and duration of the illness when treatment is started within two days of the onset of symptoms. However, while zanamivir and oseltamivir have apparently similar efficacy, they differ in their modes of delivery and tolerability. Zanamivir is delivered direct to the lungs by inhalation and is well tolerated. Oseltamivir is taken in the form of a pill but has the side-effect of producing nausea and vomiting in some patients. In the absence of a demonstrable difference in efficacy, uptake of the two drugs will depend on evaluation of the relative merits of mode of delivery and tolerability.