In contrast to methyl esters, ethyl esters are more commonly used as prodrug moieties.This is in contrast to the more polar antiviral zanamivir which is administered via the nasal rout.The ethyl ester prodrug oseltamivir; an anti-influenza (anti-viral) agent has an oral bioavailability of nearly 80%, which represents a significant improvement in bioavailability of the parent compound which is nearly 5%  [10].As mentioned before, ester prodrugs are generally exploited in order to offer increased lipophlicity to the parent drug; hence an increased intestinal absorption can be achieved.In clinical practice this improvement in bioavailability enables oral administration of oseltamivir.