In accordance with the present invention, there are provided compositions comprising zanamivir and at least one permeability enhancer. The compositions can increase the amount of zanamivir capable of being transported across a cell membrane (such as a Caco-2 cell membrane), and can increase this amount by at least 150% relative to the amount capable of being transported across the cell membrane in the absence of the permeability enhancer. Also provided are oral dosage forms of the compositions, which comprise a therapeutically effective amount of zanamivir and a permeability-enhancing amount of a permeability enhancer. The oral dosage forms can further comprise an enteric- or pH-sensitive coating or layer surrounding the composition. Also provided in accordance with the present invention are methods for treating or preventing influenza infection.
