Save that bathroom cabinet for beauty products only, no meds.
Heat, moisture and temperature change can all degrade medicines (even OTC meds and supplements), making them less effective. Try storing them in the linen closet, the bedroom, or any dry, cool place out of children's reach. If you need to tote your meds, don't carry them next to your body, like in a pants or shirt pocket. Body heat will cause them to break down as well.