For the duration of a PSK, the only meds I'd want are immodium, bendryl and an OTC analgesic. Even for a bug out bag, I don't see the need- I carry E'merg'n'C in my gear for the electrolytes, the vitamins are just a perk. In the time frames in question, you probably aren't going to get stuck by vitamin deficiencies.

That being said, for my digging in stuff, I've got the next bottle of my daily multivitamin on hand already, and bottle lasts me a couple of months.