02 and sunlight degrade medications. Store in a cool dry place with as much air out as possible. OK, sounds like storing in a sealabel container with either 02 sorbers or 02 displaced by dry ice would be the ticket eh?
I'll keep hydrogen peroxide in mind too as I'm looking for antibiotics for external application as well.
I use ammo cans with a couple of dessicant packets and that's all you need. The cans seal air tight because of a rubber ring and the dessicant removes any moisture wicked or otherwise. No need to go to the trouble of CO2.