I am sorry to hear about you loss of Penny.
I would speek w/ a vet or the rimadyl company.
I do know that one side affect is that is causes liver damage, ussually after long term use. But since she already had liver failure and then it was prescribed it may cause more damage more rapidly. I do know that my vets office does not & never had even carried that product because of the side affects.
Again I am so sorry to hear about penny. I send my sympothy!