Hi April!  We used the commercail (non-suspended) version of diazoxide.
It was still expensive ($200) but lasted much, much longer than a
suspension, being more stable.  I called the pharmaceutical company
that manufactures it to ask about added ingredients besides diazoxide
(stabalizers and such) and relayed the info to my vet, who said they were
fine.  We used this commercial brand for years.  The ferrets liked the
taste better than the expensive suspensions we tried , too.  I believe
it was chocolate mint!  And it lasted so much longer and didn't get all
crusty.  I have also found that calling around to pharmacies can mean a
big difference in the price of the same drug, which you and many on the
forum probably also know, and there are a couple ferret-friendly
pharmacies in Seattle that would go out of their way to get me the best
deals they could.  In fact, the one I got it from does ship and the woman
who was and may still be there, a pharm tech, goes to vet conferences and
learns as much as she can about ferrets and other furry creatures!  She'd
remember my Wally :)  I'd be happy to send their phone number...
 
Diazoxide was so helpful when my little Minnie got obese on pediapred,
which she could ill afford since she had a congenital heart defect.  I
slowly tapered the pred and added diazoxide and voila!  she lost weight
and regained her slim, petite little albino body... oh she was a cutey...
my eyes blur remembering...
 
Lynn, currently fuzzieless :(..... ... but still lurking
[Posted in FML issue 4590]