INFLUENZA DRUGS Adamantanes
Warning: Beginning with the 2005-2006 flu season,
widespread resistance to this class of flu agents has been
observed. Use of amantadine and rimantadine should
only be considered based on the current circulating
strain of influenza virus and after consulting current
CDC seasonal guidelines (wwv44.govif1ia),
The Amantadine has little effect during the recent HINI
“swine flu’ scare of 2009.
Amantadine
(“A Man to Dine’)
Amantadine has the narrowest spectnun. only inhibit- ing Influenza A, NOT B; the “A” is for “Araantadine.” It is
thought to do this by inhibiting viral genote.e uncoating
in the host cell. It has minimal side effects.
If given early during an influenza A infection, aman-
tadine will decrease the duration of flu symptoms. It
also helps prevent influenza A if given prophylactically. .-
For example, it can be given to nursing home residents
if there is an outbreak of influenza A.
Rimantadine appears to be as effective as amanta-
dine for the prevention of influenza A. It has less CNS
side effects (anxiety and confusion) and does not require
dose adjustments in renal failure, making it a safer
agent for the elderly.
Neuraminidase Inhibitors
gore recently a new class of agents, neuraminidase
inhibitors, with clinical activity against both influenza
A and B types have been introduced, (This includes
activity against both avian influenza A, otherwise named
‘bird flu’, and the 2009-2010 HIN1 strain of “swine
flu”.) These agents target neuraminidase
which is responsible for cleaving the bonds between
emerging virus and the cell and therefore freeing the
virus to penetrate respiratory secretions and replicate.
Resistance to neuraminidase inhibitors appears to be
slow developing. These agents are indicated for the treat-
ment of uncomplicated acute illness due to influenza and
will decrease flu-symptoms by 1 to 2 days.
Oseltamivir
Oseltartuvir s available as an oral tablet, which intw
be started within 2 days of onset of influenza symptom:,
Oseltaznivir is the only neuraminidase inhibitor used
for flu prophylaxis as well. This agent is relatively weJl
tolerated with dizziness, headache, fatigue, insomnia
and vertigo being the most frequent side effects occur-
ring in less than 2% of patients.
Zanamivir
Zanamivir is available as an intranasal spray and
oral inhaler and should be initiated within 2 days of
onset of influenza symptoms. Of course, because this _
drug is delivered through the upper respiratory tract,
it is not recommended in patients with severe chronic
obstructive pulmonary disease (COPD)), or asthma.
Nose bleed is the most characteristic side effect occur-
ring with the nasal spray in up to 4% of patients.
Peramivir
Peramivir is a newer neuraminidase inhibitor, that
was FDA approved in December 2014. It is given as a
single IV dose. It is the only IV anti-influenza agent
available and is indicated for persons unable to tolerate
oral medication or critically ill persons who are not
responding to oral regimens.