Anti-influenza viral drugs can be classified into two
groups: M2 protein inhibitors including amantadine and
rimantadine, which are effective against the type A virus,
although emergence of M2 inhibitor-resistant influenza
A viruses has occurred at high frequency in treated patients
(8, 9); and NA inhibitors such as zanamivir and
oseltamivir, which are used against both type A and type
B viruses. The NA inhibitors are more effective than the
M2 inhibitors, but influenza A viruses resistant to the NA
inhibitor oseltamivir have been found in 20% of children
treated with this drug