I've seen betta meds before, but need to run out on my lunch hour from work & grab something for my work betta. He's not doing well, and I may not be able to find the betta meds. Will regular meds do? I was thinking they'd work fine, but not sure if I need to use less than would on other fish? Or is it the same dosage?

My betta's in a 2 gallon undergravel filter, and he's almost 2 yrs old. He doesn't seem to eat anymore, and lays on his side on the gravel on the bottom. I've tried BettaZing, and it's done nothing in the past. Water changes, etc.. I just don't know if he's old & can't save him, but I want to at least try with some meds. His stomach area (?) seems to look a little bloated, but sorry, I don't have peas here at work. :/ He won't eat the pellets anymore either. I noticed that on one of his eyes, it looks like there's either a clear covering over it, or the eye is swollen. Can I just pick up regular fish meds to try & treat this for him?