Sorry I am unable to advise with regards to Patrick. His tumor was free-floating and encapsulated enough that it did not spread and did not require pain-meds.
I did however, need meds for Luna when she was diagnosed with kidney stones. She started out on metacam, and when it was found that the number of stones had increased, she was prescribed Tramadol in a compound form.
I would say that you shouldn't be too afraid of trying to make Lara as comfortable as possible. I was so thankful that Luna had something as strong as Tramadol "to take the edge off" of her pain. From whatI've heard, kidney stones hurt like heck in humans, and I don't even want to think of the pain Luna endured.
You will know when Lara needs more, and by the sounds of it, she may already need it with her back leg troubles. It is good to hear that she is still eating, drinking, and has a good attitude. TreasuredFriend always says to watch for the 3 A's; Appetite, Attitude, and Affection. If any of these are lacking, then you will know that it is time to change something for her, and that will probably include the strength of her pain meds.
Don't be afraid of the possibility of giving her Tramadol. Metacam will work up to a point, but beyond that point, Tramadol will probablybe the safest. If she gets too sleepy on it, ask the vet for a weaker dose. Luna had no side-effects from it, and was able to hang out with Patrick and Zappa, as well as get into trouble as usual. Every-bun is going to be different in how they handle any drug/pain med anyhow, so you won't know how Lara will be with it until you try.
Hope I've helped a little. So sorry you have to go through this. Knowing you're going to lose your wonderful friend sometime, anytime, isextremely difficult to deal with. It was that way for me with Luna because the vet warned me that kidney stones in rabbits are always fatal. It's the comfort-care and love that makes the difference. We on the forum are all here for you to talk with. Please don't ever feel that you are alone in any of your heartache and decisionswith Lara.
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ray:for Lara and the time she has with you. Enjoy each other, love each other, and learn from each other. You will be surprised at the things Lara has to tell you.
myheart