Please accept my sympathies on the loss of your beautiful Penny

Rimadyl is notorious for causing liver complications. I can't imagine why a vet would recommend it for a patient with an already compromised liver. Certain breeds, especially Labs are especially prone to liver damage from prolonged use. Even otherwise healthy dogs are usually monitored (blood work) while on it. Although I know it has been known to be of great help to arthritic dogs, my vet very rarely if ever prescribes it.

Bless you dear Penny. No more pain or suffering beautiful girl. I know my Jing is welcoming you at the Rainbow Bridge with open paws.