Ivermectin (oral info):
Well, I am not a vet, but I can look up the info to let the vets speak
for themselves.

In Dr. Karen Purcell's vet text, _Essentials of Ferrets, a Guide for
Practioners_ you will notice that there *IS* oral dosing provided, and
there is no way Karen would do that if she were worried.  Plus, she did
not add a caution in the comments.  See page 27 for:

"Ivermectin
0.006 mg/kg q 30 d PO"
[heartworm prevention]

"0.5 mg/kg PO, SC"
[dosing for after destroying adult heart worms]

"0.5-1.0 mg/kg PO, SC"
[sarcoptic mange, ear mites]

On page 439 of _Ferrets, Rabbits and Rodents, Clinical Medicine and
Surgery_ Doctors Katy Quesenberry and James Carpenter also provide oral
dosing for ferrets.  You will notice that the concerns for the rabbits
and rodents for this med are different, though, so for them there is not
oral dosing.

if you want that dosing info, too, I will copy it for you.

Notice Dr. Ruth Heller using it in
http://ferrethealth.org/archive/browse.php?msg=SG14589

Dr. Bruce Williams can be found commenting in
http://ferrethealth.org/archive/browse.php?msg=YG8727

and there are more in the archives.

Honestly, I would go by what the VETS say, and I think you are inclined
in that direction, too, from the way that you worded your request

One of the Frontline Golden Oldies:
http://fhl.sonic-weasel.org/browse.php?msg=SG7520

Fostering: I was actually surprised to find that a shelter covered day
to day expenses other than just medical.  The latter is what I have
usually read of happening.

-- Sukie (not a vet, and not speaking for any of the below in my
private posts)
Recommended health resources to help ferrets and the people who love
them:
Ferret Health List
http://www.smartgroups.com/groups/ferrethealth
FHL Archives
http://ferrethealth.org/archive/
AFIP Ferret Pathology
http://www.afip.org/ferrets/index.html
Miamiferrets
http://www.miamiferret.org/fhc/
International Ferret Congress Critical References
http://www.ferretcongress.org
[Posted in FML issue 5274]