From the FDA site:
1. Check for a take-back program in your area. Basically call the dump.
2. "If no disposal instructions are given on the prescription drug labeling and no take-back program is available in your area, throw the drugs in the household trash following these steps:
Remove them from their original containers and mix them with an undesirable substance, such as used coffee grounds, dirt or kitty litter (this makes the drug less appealing to children and pets, and unrecognizable to people who may intentionally go through the trash seeking drugs).
Place the mixture in a sealable bag, empty can or other container to prevent the drug from leaking or breaking out of a garbage bag."
In short, mix it with some garbage and throw it out in a way so nobody will feel inclined to root through your garbage for pills.
