Cats and insipidus

my 7 year old cat has been drinking/urinating alot, eating and sleeping alot for the past 4-5 months - getting worse with each passing day.  We have taken her to vets and told that her blood tests were fine and the only thing that was abnormal on her urine tests was her 'specific gravity' levels were very low - at 1.012.  Vet gave an uncertain diagnosis of diabetes insipidus and started her on DDAVP hormones in eye drop format.  Of course this is very difficult to administer to her as most of the drops drip away once she closes her eyes - we tried to put under her bottom eyelid but she becomes very angry and tries to bite us now!  We are not sure if this is working and it is getting very expensive with all the vet visits and medication etc.  Any ideas of what other forms of treatment are available and/or can this be fatal if left untreated?

[opus88]

well that is really uncommon, has the Vet ruled out CRF?....
since I don't have any personal knowledge of insipidus I found a Veterinary site that should give you more info.

http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/40507.htm&word=feline%2cdiabetes%2cinsipidus

I do know DDAVP for humans is VERY expensive and I assume its the same for pets....the article dose say the drops can also be administered to the nasal mucosa( I have done this for humans but not for pets).....it may mean a different prescription so talk to your Vet about this...IMO nasal drops would be easier to administer b/c your not attempting to both hold the cat and the eyelid open at the same time...

NOTE diabetes of any form left untreated is fatal..please don't withhold treatment, talk to your Vet about alternatives...please.
keep us informed....and good luck.♥