Not sure what you can do about miscast potions. Most players probably won't hit the f key accidentally like I did.
I'm personally a fan of minimalist control schemes, so I'd consider removing the potion key altogether and make it auto-consume when needed. But I guess then you'd loose the implicit press-your-luck mechanic that manual potions offer.
I guess the ultimate solution would be user key remapping, but coding that means time not spent coding something else.