Welcome, Archie-Neil
so sorry to hear about your kitty
I think you will find a difference in your kitty's health if you change her food to a quality canned
. Nature's Variety makes Duck, Rabbit and Lamb flavours you can try if your cat has not had these meats before.
As for Amitriptyline, it is commonly used in cats but not all that safe. I have talked extensively to my vet about it when I had Sweet Pea on it for a couple of months. He only prescribes it to young, healthy cats and monitors blood work every three months to monitor the liver.
Here is some info:
http://www.vetinfo.com/side-effects-...line-cats.html
If the blood is bright red, then the bleeding is low in the colon, if it is darker or the stools are black or tarry, then it is much farther up in the tract.