Sorry to hear this is going on.
Certainly with any drug there can be side effects. What you are seeing could be related to the drug itself.
I've attached a link to the drug itself, including side effects.
Equally likely is that this behavior is secondary to the priXXXXX XXXXXver problem. Liver issues are the usual reason this drug is prescribed.
If the condition continues, see your vet. There are other formulations of the drug that may be effective, and they may improve on those.
Good luck, and let me know what happens.