[RainMan]

I would question storing them in the freezer. Two things that CAN change chemistry over time are light and heat, so putting something in a dark refridgerator at a low constant temperature would eliminate those variables.

Putting it in the freezer would not be recommended however, because just as excessive heat can change chemistry, so can excessive cold. Freezer burn can happen to medicine just as it can happen to that nice steak or quart of ice cream. The moisture in your medicine will dessicate, which can cause chemical bonds to fail. Also, if your medicine is a liquid, freezing could cause the product to expand and break the bottle. Caplets can also be broken by freezing them.

[Nepeta]

I would question storing them in the freezer.

Long-term storage of chemicals used as standards is commonly refrigeration or in a freezer--but if you are going to do this with medication, put the prescription bottle inside of an airtight container. (Throwing away the original labeling is NOT a good idea.)