I think the medicines should have shorter cool down time.
And furthermore, the timer shouldn't be the same for all the items.

It is really impractical to have 5 minutes cool down for Echo Drops... if a monster has a move that silences you, it will usually use it more than once in 5 minutes.

What if a healer is out of HP and MP, I use a pot for MP and then I have to wait 5 mins for the HP one?

I suggest every group of items have different timers. One for ethers, one for potions and then individual timers for crucial medicines such as Antidotes and Echo Drops.
There is no point to purchase these items (and alchemists to make them) if you can't really use them very well.