For me it doesn't matter. Dragging it to the hotbar, equipping it and then checking in the inventory returns the same result. It appears a First Aid Kit is treated the same as e.g. a can. There it doesn't really matter which one you drink first if you have two.
May 10 2016
Yes it appears so, but it makes first aid kits hard to use. And normally you can swap everything in your hands, so why not two first aid kits? (talking from a user experience perspective) Also I suppose this behaviour is the same for any container as well (like that yellow protector case), where it might be problematic as well.
Eat all can or food +1
@ItsMe360Nation: Please elaborate! I think eating a whole can of beans if you're starving isn't unrealistic. I suppose you didn't mean to say this, but without specifying, people can't really tell what you mean.