Over a year ago I had an opperation, and when they sent me home they gave me prescription Tylonol with Codine. At this point, I figured I probably couldn't use it, and I couldn't give it to anyone ...
If it's expired, your pharmacy may accept it for disposal. If not, put the loose pills in a Ziploc bag and add some flour, water and kitty litter. Shake until it's well blended and then dispose of the whole thing in your garbage (don't unzip the bag).
Never flush medicine down the toilet or put it down the drain as it can ultimately leach into your community's drinking water.