I found very small zip lock bags in a craft store. They're intended for beads or tiny parts. Some might put illegal substances in them....

I put OTC meds in these, labeled with a sharpie, and I cut out the name portion of the original package. I put prescription drugs in them, and affix the label that goes on the original bottle. Pharmacists will print an extra label for you if you ask.

Then everything goes into a air/water/crush proof box like an otter box.