Looking through the other thread, some useful, OTC medications to have on hand:
diphenhydramine (Benadryl)
caffeine pills
4 baby aspirin (especially if you are a male over 40 with a history of heart disease in your family)

These could also be nice to have:
an antacid
immodium

I am allergic to bees, so I always carry Benadryl, caffiene pills, my rescue inhaler, and an epipen in my saddle bag. The last two items on the list are Rx only in the US.

If you really want to Boy Scout it up and be prepared for massive bleeding, take along some feminine sanitary napkins, super size. They make great trauma dressings, and don't stick to hair. That's what we used on horses in pony club, but they're not sterile.