Amantadine as an anti-flu drug 
Author Message
 Amantadine as an anti-flu drug

Quote:

>I'd be interested in comments on the drug amantadine as a treatment for
>certain flu (specifically, Influenza A) viruses.
>I was surprised that any anti-flu drug existed at all.  Last I had
>known, once you got the flu, you just had to let it take its course.

Amantadine was introduced as a prophylactic agent against Influenza A
infection, and has been used in this capacity for about 20-25 years.
It's only in the past 5-7 years that it has been approved for the
treatment of Influenza A after an infection has been established and
flu symptoms have appeared.  One reason for this is that it's a whole
lot harder to demonstrate efficacy in the treatment of a disease like
flu (as opposed to its prevention), since its course can be so
variable.  It's also completely ineffective against Influenza B, and
it's often difficult to know what strain a particular case is unless
there's a widespread outbreak.

Quote:
>In any case, I started taking amantadine yesterday afternoon, and my
>fever started going down within hours (back to the vicinity of 37.5C).
>No way, of course, to be sure whether this was because of the drug or
>if it was about to get better anyway.

A few years ago, I came down with the flu 2 days before Christmas,
and asked for (and received) an Rx for amantadine.  It was difficult
to say in this particular case whether it had much of an effect.
I did feel somewhat better, but it still took me a week to shake it.
The effect wasn't clear cut enough for me to attribute it to the
drug (or not.)

Quote:
>I understand that amantadine is also useful in treating Parkinson's
>disease.  Was this what it was first developed/discovered for, with the
>anti-flu effects noticed only later?

No, it was the other way around.  Its ameliorative effects in certain
patients with Parkinsonism were observed serendipitously after it was
administered as flu prophylaxis.  You see, the elderly and infirm are a
prime risk group for severe flu, and so are more likely to receive
prophylaxis.  A significant subgroup of these would be individuals with
Parkinsonism.  Amantadine seems to exert its anti-Parkinson's effect by
facilitating the release of dopamine within a part of the brain known
as the substantia nigra.

Quote:
>My doctor also warned that there was a (very small) possibility that
>amantadine might make me drowsy, give me hallucinations, or even make
>me psychotic...  Can anyone on the net supply more details
>as to what kind of mind-altering side effects have been seen with
>amantadine?

These kinds of side effects have occurred most frequently in the
elderly, who tend to be quite sensitive to {*filter*} with central nervous
system activity, and in patients with Parkinsonism who might also be
taking {*filter*} which interact with amantadine and which may contribute
in their own way to such side-effects.  If you are an otherwise healthy
{*filter*}, such untoward effects would be rather surprising.  In most
people, the drug produces no subjective side-effects.

Quote:
>Amantadine is supposedly =not= a general antiviral drug, but has only
>been observed to be effective against Influenza A infections.  Appar-
>ently, though, it works in such a way that it'll fight multiple strains
>of Influenza A (as opposed to a vaccine).  Are there any hopes that the
>discovery of amantadine may lead to other, more general treatments for
>influenza and other viral infections?

Well, just from the impression I get (I haven't followed the research
or the literature lately) amantadine seems like a remarkable, but
somewhat dead-end, drug, at least as far as producing important
spin-offs is concerned.  It apparently interferes with the ability of
the Influenza A virus to attach to and infect cells; I don't believe it
interferes with replication of the virus.  This is apparently an effect
sufficiently unique to Influenza A (and still poorly enough understood)
that it hasn't illuminated the basic research on anti-virals.  I may
follow this up with a literature search though; you've piqued my interest.

Quote:
>Finally, is there a realistic danger that the overuse of amantadine may
>result in the proliferation of hardier flu viruses

Well, I don't know about "hardier", but I suppose it could encourage
the selection of viruses which are resistant to the mechanism of
action of the drug.  I don't know whether this is a serious concern.
(In some sense it isn't, because amantadine is generally used as
prophylaxis only when the current year's vaccine isn't available
or practical.)

--
Steve Dyer




Sun, 02 May 1993 06:47:45 GMT
 Amantadine as an anti-flu drug
Just a quick note:

Amantadine apparently interferes with the uncoating of the virus,
which is why is was originally used as a prophylactic after exposure
and prior to symptoms.

Linda Li
Boston University School of Medicine
Boston, MA



Sun, 02 May 1993 20:08:21 GMT
 Amantadine as an anti-flu drug

Quote:

>Amantadine apparently interferes with the uncoating of the virus,
>which is why is was originally used as a prophylactic after exposure
>and prior to symptoms.

Yes, I wrote that off the top of my head yesterday.  When I looked
it up last night, there seemed to be consensus that the drug acts in
two ways, though probably through the same mechanism: by interfering
with the uncoating of the virus during initial infection and also by
interfering with assembly of the viral particles.   The theory that
it worked by interfering with penetration was an early conjecture
before its mechanism of action was investigated.

--
Steve Dyer




Mon, 03 May 1993 00:26:11 GMT
 
 [ 3 post ] 

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