Open the medicine chest and begin dumping. Check expiration dates. Anything too old gets tossed out. The toothpaste that nobody likes, even if half a tube still remains, goes. Call your pharmacist to inquire about the expiration of any prescription drugs.
Most pharmacists are very happy to oblige.
They don't ask where you bought the product, so don't feel shy if you've bought from several places. They will honestly tell you what is wise to keep and what is best discarded. They will also tell you the safest way to dispose of each item. Again, it's best to ask your pharmacist. While you're at it, make a written note of anything that you're running low on, and any first-aid supplies that you probably should have on hand, but don't.