I have EDC one, car one, bug in one, bug out one. Each progressively more advanced.
We bug out in our RV which has all those things already in it. We live in hurricane country which makes us ready to bug out 24/7. Already bugged out 3 times now in 20 years. Harvey was the last time.
A BOB should have a means of starting a fire, a knife for obtaining wood for fire, building a shelter, and obtaining food, water or a way to filter water.
There are always more items.
Firestarter / Matches (both)
Knife
Water
550 cord
Tarp and / or trash bag
and yes, any prescription medicine you may need.
With a knife, you can make kindling and help start a fire, help gather poles for building a shelter, and with the 550 cord and tarp you have the means to make a quick shelter if you can not build one, water is a must, and a way to filter water (which can be done with a plastic bottle and straw or grasses, sand, gravel, and then boil it) A trash bag can be used as a ground cover and / or a rain poncho.
So, you can do without the tarp and trash bag, but you really should have your prescription medicine, a way to start a fire, and a knife to help build shelter and water or a means of filtering… so there are at least 4 items,
and this would not be a BOB. It might be a quick get home bag, or emergency survival bag, but a BOB should have more than three or four items.