Re: Prescription medicines for first aid kit
I've used the UN rehydration recipe for years, and wanted to also mention it is dirt cheap, easily pre-mixed and carried so you just add water, and it beats the heck out of Gatoraide or anything else to keep you hydrated on a hot day.
OTOH it always tastes like old socks, no matter how you try to flavor it, i.e. by adding lemonade powder instead of sugar. Which can be a good thing, because no one wants to borrow it.