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Hello. Thanks for the question.
It does sound like you are seeing a side effect to Buprenorphine (Buprenex). This is a very safe pain medication, but cats can act pretty goofy on it. Some will get lethargic. Some will get dilated pupils and act high. Some will be more affectionate. There are many different effects that we can see. You're seeing the more hyperactive/ high look.
You could try giving a lower dose. It's probably drawn up in syringes, so you could give 1/2 of what they dosed. You could also go less frequently and only give it every 12 hours. That may help with these signs. If all else fails, you could stop the pain meds. It's been 3 days now, so she could probably have them stopped.
I hope this helps, let me know if you have any other questions.