Arthritis and pain meds not working anymore. I know what to do. But…

Hello. My hounds name is Ronnie he’s 13 1/2 years old. He’s been in monthly arthritis shot (Librela) for a year, I saw him struggling to get out of bed so I knew immediately something was wrong. Took him to the vet and put him in two more pain meds. ( carprofen and gabapentin) soon after he struggled to walk, look confused and loosing his balance. Took him to the vet again and they told me he’s in extreme pain and that those are the side affects of his meds. I can’t see my Ronnie like this those side effects are awful, so they wanna put him on cbd tablets and see what happens. BUT I can’t let my best friend have this pain and wait for the results. Do I give it one more try or I wait? he will probably be in pain again. He is in the emergency section right now with an iv for pain and picking him up tomorrow. Any help would be appreciated. Thanks.