As noted - always bring prescription drugs in their original bottles with info. I'd also note that the zipper-case is very unlikely to be truly water-proof.
I usually carry a few of these with me when traveling
Osprey ultralight dry bag -
Things that shouldn't get wet (or already are) goes in them, and the design makes it easy to clip to the outside of your bags if necessary to create more effective-volume. For example, it's how I usually carry around my Bose QC headset these days. Bright red bag - hard to forget, and with an add-on carabiner, I can clip it to seat back pocket (or belt) for easy access.