I have found a few threads mentioning this, but none mentioned any "cure" for it. My cat has noticed that after taking relatively high doses of opiods (specifically hydromorphone
[60mg+ but has also noticed this at even 30mg at times] in her case), she often has a hangover the next day- usually consisting of fatigue and headache (sometimes severe). My cat doesn't consider this to be withdrawals, given what she's read about them and her use schedule (sometimes a few times a week at most and on those days, only one dose in the evening) and the duration of symptoms (sometimes only the morning after and occasionally the whole day).
Is there anything my cat can do to help with these symptoms, other than taking a small lower dose of more medication? She has tried naproxen/excedrine/prescribed migraine medication, as well as hydrating well. My cat realizes this may be a "rebound" headache as well, and it definitely doesn't happen every time she uses, even at her somewhat high doses- but almost every time, she experiences fatigue the next day, even after adequate sleep.